entry : documentProperties.entrySet()) {
+ String key = entry.getKey();
+ Object value = entry.getValue();
+
+ // Append key-value pair
+ builder.append("[").append(key).append(" : ").append(value).append("]");
+
+ // Add comma if not last property
+ if (++currentPropertyIndex < numProperties) {
+ builder.append(", ");
+ }
+ }
+
builder.append("]");
return builder.toString();
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/App.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/App.java
index b881ee7ac0f6..607b4a7f7913 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/App.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/App.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,13 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument;
import com.iluwatar.abstractdocument.domain.Car;
import com.iluwatar.abstractdocument.domain.enums.Property;
import java.util.List;
import java.util.Map;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
/**
* The Abstract Document pattern enables handling additional, non-static properties. This pattern
@@ -38,30 +38,37 @@
* In Abstract Document pattern,({@link AbstractDocument}) fully implements {@link Document})
* interface. Traits are then defined to enable access to properties in usual, static way.
*/
+@Slf4j
public class App {
- private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
-
/**
- * Executes the App.
+ * Program entry point.
+ *
+ * @param args command line args
*/
- public App() {
+ public static void main(String[] args) {
LOGGER.info("Constructing parts and car");
- var wheelProperties = Map.of(
- Property.TYPE.toString(), "wheel",
- Property.MODEL.toString(), "15C",
- Property.PRICE.toString(), 100L);
+ var wheelProperties =
+ Map.of(
+ Property.TYPE.toString(), "wheel",
+ Property.MODEL.toString(), "15C",
+ Property.PRICE.toString(), 100L);
- var doorProperties = Map.of(
- Property.TYPE.toString(), "door",
- Property.MODEL.toString(), "Lambo",
- Property.PRICE.toString(), 300L);
+ var doorProperties =
+ Map.of(
+ Property.TYPE.toString(), "door",
+ Property.MODEL.toString(), "Lambo",
+ Property.PRICE.toString(), 300L);
- var carProperties = Map.of(
- Property.MODEL.toString(), "300SL",
- Property.PRICE.toString(), 10000L,
- Property.PARTS.toString(), List.of(wheelProperties, doorProperties));
+ var carProperties =
+ Map.of(
+ Property.MODEL.toString(),
+ "300SL",
+ Property.PRICE.toString(),
+ 10000L,
+ Property.PARTS.toString(),
+ List.of(wheelProperties, doorProperties));
var car = new Car(carProperties);
@@ -69,20 +76,13 @@ public App() {
LOGGER.info("-> model: {}", car.getModel().orElseThrow());
LOGGER.info("-> price: {}", car.getPrice().orElseThrow());
LOGGER.info("-> parts: ");
- car.getParts().forEach(p -> LOGGER.info("\t{}/{}/{}",
- p.getType().orElse(null),
- p.getModel().orElse(null),
- p.getPrice().orElse(null))
- );
- }
-
- /**
- * Program entry point.
- *
- * @param args command line args
- */
- public static void main(String[] args) {
- new App();
+ car.getParts()
+ .forEach(
+ p ->
+ LOGGER.info(
+ "\t{}/{}/{}",
+ p.getType().orElse(null),
+ p.getModel().orElse(null),
+ p.getPrice().orElse(null)));
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/Document.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/Document.java
index d0eb85f34c78..79a51b610337 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/Document.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/Document.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,22 +22,19 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Stream;
-/**
- * Document interface.
- */
+/** Document interface. */
public interface Document {
/**
* Puts the value related to the key.
*
- * @param key element key
+ * @param key element key
* @param value element value
* @return Void
*/
@@ -52,7 +51,7 @@ public interface Document {
/**
* Gets the stream of child documents.
*
- * @param key element key
+ * @param key element key
* @param constructor constructor of child class
* @return child documents
*/
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Car.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Car.java
index bf68d40e57fe..93fbbb9c1eae 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Car.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Car.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +22,15 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument.domain;
import com.iluwatar.abstractdocument.AbstractDocument;
import java.util.Map;
-/**
- * Car entity.
- */
+/** Car entity. */
public class Car extends AbstractDocument implements HasModel, HasPrice, HasParts {
public Car(Map properties) {
super(properties);
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasModel.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasModel.java
index 76d7d743139d..6f517588e5a0 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasModel.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasModel.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,20 +22,16 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument.domain;
import com.iluwatar.abstractdocument.Document;
import com.iluwatar.abstractdocument.domain.enums.Property;
import java.util.Optional;
-/**
- * HasModel trait for static access to 'model' property.
- */
+/** HasModel trait for static access to 'model' property. */
public interface HasModel extends Document {
default Optional getModel() {
return Optional.ofNullable((String) get(Property.MODEL.toString()));
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasParts.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasParts.java
index 8ecfa85fb5eb..8bffa753e6ef 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasParts.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasParts.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,21 +22,16 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument.domain;
import com.iluwatar.abstractdocument.Document;
import com.iluwatar.abstractdocument.domain.enums.Property;
import java.util.stream.Stream;
-/**
- * HasParts trait for static access to 'parts' property.
- */
+/** HasParts trait for static access to 'parts' property. */
public interface HasParts extends Document {
-
default Stream getParts() {
return children(Property.PARTS.toString(), Part::new);
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasPrice.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasPrice.java
index 9a95f2a514db..ce876e5faf54 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasPrice.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasPrice.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,21 +22,16 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument.domain;
import com.iluwatar.abstractdocument.Document;
import com.iluwatar.abstractdocument.domain.enums.Property;
import java.util.Optional;
-/**
- * HasPrice trait for static access to 'price' property.
- */
+/** HasPrice trait for static access to 'price' property. */
public interface HasPrice extends Document {
-
default Optional getPrice() {
return Optional.ofNullable((Number) get(Property.PRICE.toString()));
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasType.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasType.java
index b1d5bd6b563f..5e0f49df7b7b 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasType.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/HasType.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,21 +22,16 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument.domain;
import com.iluwatar.abstractdocument.Document;
import com.iluwatar.abstractdocument.domain.enums.Property;
import java.util.Optional;
-/**
- * HasType trait for static access to 'type' property.
- */
+/** HasType trait for static access to 'type' property. */
public interface HasType extends Document {
-
default Optional getType() {
return Optional.ofNullable((String) get(Property.TYPE.toString()));
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Part.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Part.java
index 996598a92712..6eec08b0d2a4 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Part.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/Part.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +22,15 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument.domain;
import com.iluwatar.abstractdocument.AbstractDocument;
import java.util.Map;
-/**
- * Part entity.
- */
+/** Part entity. */
public class Part extends AbstractDocument implements HasType, HasModel, HasPrice {
public Part(Map properties) {
super(properties);
}
-
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/enums/Property.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/enums/Property.java
index 640f0ed83f1d..3e0d6d10ab1f 100644
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/enums/Property.java
+++ b/abstract-document/src/main/java/com/iluwatar/abstractdocument/domain/enums/Property.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,13 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument.domain.enums;
-/**
- * Enum To Describe Property type.
- */
+/** Enum To Describe Property type. */
public enum Property {
-
- PARTS, TYPE, PRICE, MODEL
+ PARTS,
+ TYPE,
+ PRICE,
+ MODEL
}
diff --git a/abstract-document/src/main/java/com/iluwatar/abstractdocument/module-info.java b/abstract-document/src/main/java/com/iluwatar/abstractdocument/module-info.java
deleted file mode 100644
index 9121f004990b..000000000000
--- a/abstract-document/src/main/java/com/iluwatar/abstractdocument/module-info.java
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-module com.iluwatar.abstractdocument {
- requires org.slf4j;
-}
\ No newline at end of file
diff --git a/abstract-document/src/test/java/com/iluwatar/abstractdocument/AbstractDocumentTest.java b/abstract-document/src/test/java/com/iluwatar/abstractdocument/AbstractDocumentTest.java
index d7fe5688d262..a098517c3a69 100644
--- a/abstract-document/src/test/java/com/iluwatar/abstractdocument/AbstractDocumentTest.java
+++ b/abstract-document/src/test/java/com/iluwatar/abstractdocument/AbstractDocumentTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,43 +22,38 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.*;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.junit.jupiter.api.Test;
-/**
- * AbstractDocument test class
- */
-public class AbstractDocumentTest {
+/** AbstractDocument test class */
+class AbstractDocumentTest {
private static final String KEY = "key";
private static final String VALUE = "value";
- private class DocumentImplementation extends AbstractDocument {
+ private static class DocumentImplementation extends AbstractDocument {
DocumentImplementation(Map properties) {
super(properties);
}
}
- private DocumentImplementation document = new DocumentImplementation(new HashMap<>());
+ private final DocumentImplementation document = new DocumentImplementation(new HashMap<>());
@Test
- public void shouldPutAndGetValue() {
+ void shouldPutAndGetValue() {
document.put(KEY, VALUE);
assertEquals(VALUE, document.get(KEY));
}
@Test
- public void shouldRetrieveChildren() {
+ void shouldRetrieveChildren() {
var children = List.of(Map.of(), Map.of());
document.put(KEY, children);
@@ -67,18 +64,67 @@ public void shouldRetrieveChildren() {
}
@Test
- public void shouldRetrieveEmptyStreamForNonExistingChildren() {
+ void shouldRetrieveEmptyStreamForNonExistingChildren() {
var children = document.children(KEY, DocumentImplementation::new);
assertNotNull(children);
assertEquals(0, children.count());
}
@Test
- public void shouldIncludePropsInToString() {
+ void shouldIncludePropsInToString() {
var props = Map.of(KEY, (Object) VALUE);
var document = new DocumentImplementation(props);
assertTrue(document.toString().contains(KEY));
assertTrue(document.toString().contains(VALUE));
}
+ @Test
+ void shouldHandleExceptionDuringConstruction() {
+ Map invalidProperties =
+ null; // Invalid properties, causing NullPointerException
+
+ // Throw null pointer exception
+ assertThrows(
+ NullPointerException.class,
+ () -> {
+ // Attempt to construct a document with invalid properties
+ new DocumentImplementation(invalidProperties);
+ });
+ }
+
+ @Test
+ void shouldPutAndGetNestedDocument() {
+ // Creating a nested document
+ DocumentImplementation nestedDocument = new DocumentImplementation(new HashMap<>());
+ nestedDocument.put("nestedKey", "nestedValue");
+
+ document.put("nested", nestedDocument);
+
+ // Retrieving the nested document
+ DocumentImplementation retrievedNestedDocument =
+ (DocumentImplementation) document.get("nested");
+
+ assertNotNull(retrievedNestedDocument);
+ assertEquals("nestedValue", retrievedNestedDocument.get("nestedKey"));
+ }
+
+ @Test
+ void shouldUpdateExistingValue() {
+ // Arrange
+ final String key = "key";
+ final String originalValue = "originalValue";
+ final String updatedValue = "updatedValue";
+
+ // Initializing the value
+ document.put(key, originalValue);
+
+ // Verifying that the initial value is retrieved correctly
+ assertEquals(originalValue, document.get(key));
+
+ // Updating the value
+ document.put(key, updatedValue);
+
+ // Verifying that the updated value is retrieved correctly
+ assertEquals(updatedValue, document.get(key));
+ }
}
diff --git a/abstract-document/src/test/java/com/iluwatar/abstractdocument/AppTest.java b/abstract-document/src/test/java/com/iluwatar/abstractdocument/AppTest.java
index aed63f303181..16dcba0db37f 100644
--- a/abstract-document/src/test/java/com/iluwatar/abstractdocument/AppTest.java
+++ b/abstract-document/src/test/java/com/iluwatar/abstractdocument/AppTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +22,23 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
import org.junit.jupiter.api.Test;
-/**
- * Simple App test
- */
-public class AppTest {
+/** Simple App test */
+class AppTest {
+ /**
+ * Issue: Add at least one assertion to this test case.
+ *
+ * Solution: Inserted assertion to check whether the execution of the main method in {@link
+ * App} throws an exception.
+ */
@Test
- public void shouldExecuteAppWithoutException() {
- App.main(null);
+ void shouldExecuteAppWithoutException() {
+ assertDoesNotThrow(() -> App.main(null));
}
-
}
diff --git a/abstract-document/src/test/java/com/iluwatar/abstractdocument/DomainTest.java b/abstract-document/src/test/java/com/iluwatar/abstractdocument/DomainTest.java
index 5b1311ff6af9..fc29dea45c43 100644
--- a/abstract-document/src/test/java/com/iluwatar/abstractdocument/DomainTest.java
+++ b/abstract-document/src/test/java/com/iluwatar/abstractdocument/DomainTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractdocument;
import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -32,10 +33,8 @@
import java.util.Map;
import org.junit.jupiter.api.Test;
-/**
- * Test for Part and Car
- */
-public class DomainTest {
+/** Test for Part and Car */
+class DomainTest {
private static final String TEST_PART_TYPE = "test-part-type";
private static final String TEST_PART_MODEL = "test-part-model";
@@ -45,12 +44,12 @@ public class DomainTest {
private static final long TEST_CAR_PRICE = 1L;
@Test
- public void shouldConstructPart() {
- var partProperties = Map.of(
- Property.TYPE.toString(), TEST_PART_TYPE,
- Property.MODEL.toString(), TEST_PART_MODEL,
- Property.PRICE.toString(), (Object) TEST_PART_PRICE
- );
+ void shouldConstructPart() {
+ var partProperties =
+ Map.of(
+ Property.TYPE.toString(), TEST_PART_TYPE,
+ Property.MODEL.toString(), TEST_PART_MODEL,
+ Property.PRICE.toString(), (Object) TEST_PART_PRICE);
var part = new Part(partProperties);
assertEquals(TEST_PART_TYPE, part.getType().orElseThrow());
assertEquals(TEST_PART_MODEL, part.getModel().orElseThrow());
@@ -58,16 +57,15 @@ public void shouldConstructPart() {
}
@Test
- public void shouldConstructCar() {
- var carProperties = Map.of(
- Property.MODEL.toString(), TEST_CAR_MODEL,
- Property.PRICE.toString(), TEST_CAR_PRICE,
- Property.PARTS.toString(), List.of(Map.of(), Map.of())
- );
+ void shouldConstructCar() {
+ var carProperties =
+ Map.of(
+ Property.MODEL.toString(), TEST_CAR_MODEL,
+ Property.PRICE.toString(), TEST_CAR_PRICE,
+ Property.PARTS.toString(), List.of(Map.of(), Map.of()));
var car = new Car(carProperties);
assertEquals(TEST_CAR_MODEL, car.getModel().orElseThrow());
assertEquals(TEST_CAR_PRICE, car.getPrice().orElseThrow());
assertEquals(2, car.getParts().count());
}
-
}
diff --git a/abstract-factory/README.md b/abstract-factory/README.md
index 6a840f316974..ee9823a39a5f 100644
--- a/abstract-factory/README.md
+++ b/abstract-factory/README.md
@@ -1,24 +1,32 @@
---
-layout: pattern
-title: Abstract Factory
-folder: abstract-factory
-permalink: /patterns/abstract-factory/
-categories: Creational
-tags:
- - Gang of Four
+title: "Abstract Factory Pattern in Java: Mastering Object Creation Elegantly"
+shortTitle: Abstract Factory
+description: "Learn the Abstract Factory pattern in Java with real-world examples, class diagrams, and tutorials. Understand its intent, applicability, benefits, and known uses to enhance your design pattern knowledge."
+category: Creational
+language: en
+tag:
+ - Abstraction
+ - Decoupling
+ - Gang of Four
+ - Instantiation
+ - Polymorphism
---
## Also known as
-Kit
-## Intent
-Provide an interface for creating families of related or dependent
-objects without specifying their concrete classes.
+* Kit
-## Explanation
-Real world example
+## Intent of Abstract Factory Design Pattern
-> To create a kingdom we need objects with common theme. Elven kingdom needs an Elven king, Elven castle and Elven army whereas Orcish kingdom needs an Orcish king, Orcish castle and Orcish army. There is a dependency between the objects in the kingdom.
+The Abstract Factory pattern in Java provides an interface for creating families of related or dependent objects without specifying their concrete classes, enhancing modularity and flexibility in software design.
+
+## Detailed Explanation of Abstract Factory Pattern with Real-World Examples
+
+Real-world example
+
+> Imagine a furniture company that uses the Abstract Factory pattern in Java to produce various styles of furniture: modern, Victorian, and rustic. Each style includes products like chairs, tables, and sofas. To ensure consistency within each style, the company uses an Abstract Factory pattern.
+>
+> In this scenario, the Abstract Factory is an interface for creating families of related furniture objects (chairs, tables, sofas). Each concrete factory (ModernFurnitureFactory, VictorianFurnitureFactory, RusticFurnitureFactory) implements the Abstract Factory interface and creates a set of products that match the specific style. This way, clients can create a whole set of modern or Victorian furniture without worrying about the details of their instantiation. This maintains a consistent style and allows easy swapping of one style of furniture for another.
In plain words
@@ -28,174 +36,192 @@ Wikipedia says
> The abstract factory pattern provides a way to encapsulate a group of individual factories that have a common theme without specifying their concrete classes
-**Programmatic Example**
+Class diagram
+
+
+
+## Programmatic Example of Abstract Factory in Java
+
+To create a kingdom using the Abstract Factory pattern in Java, we need objects with a common theme. The elven kingdom needs an elven king, elven castle, and elven army whereas the orcish kingdom needs an orcish king, orcish castle, and orcish army. There is a dependency between the objects in the kingdom.
-Translating the kingdom example above. First of all we have some interfaces and implementation for the objects in the kingdom
+Translating the kingdom example above. First of all, we have some interfaces and implementation for the objects in the kingdom.
```java
public interface Castle {
- String getDescription();
+ String getDescription();
}
+
public interface King {
- String getDescription();
+ String getDescription();
}
+
public interface Army {
- String getDescription();
+ String getDescription();
}
// Elven implementations ->
public class ElfCastle implements Castle {
- static final String DESCRIPTION = "This is the Elven castle!";
- @Override
- public String getDescription() {
- return DESCRIPTION;
- }
+ static final String DESCRIPTION = "This is the elven castle!";
+
+ @Override
+ public String getDescription() {
+ return DESCRIPTION;
+ }
}
+
public class ElfKing implements King {
- static final String DESCRIPTION = "This is the Elven king!";
- @Override
- public String getDescription() {
- return DESCRIPTION;
- }
+ static final String DESCRIPTION = "This is the elven king!";
+
+ @Override
+ public String getDescription() {
+ return DESCRIPTION;
+ }
}
+
public class ElfArmy implements Army {
- static final String DESCRIPTION = "This is the Elven Army!";
- @Override
- public String getDescription() {
- return DESCRIPTION;
- }
-}
+ static final String DESCRIPTION = "This is the elven Army!";
-// Orcish implementations similarly...
+ @Override
+ public String getDescription() {
+ return DESCRIPTION;
+ }
+}
+// Orcish implementations similarly -> ...
```
-Then we have the abstraction and implementations for the kingdom factory
+Then we have the abstraction and implementations for the kingdom factory.
```java
public interface KingdomFactory {
- Castle createCastle();
- King createKing();
- Army createArmy();
+ Castle createCastle();
+
+ King createKing();
+
+ Army createArmy();
}
public class ElfKingdomFactory implements KingdomFactory {
- public Castle createCastle() {
- return new ElfCastle();
- }
- public King createKing() {
- return new ElfKing();
- }
- public Army createArmy() {
- return new ElfArmy();
- }
-}
-public class OrcKingdomFactory implements KingdomFactory {
- public Castle createCastle() {
- return new OrcCastle();
- }
- public King createKing() {
- return new OrcKing();
- }
- public Army createArmy() {
- return new OrcArmy();
- }
-}
-```
+ @Override
+ public Castle createCastle() {
+ return new ElfCastle();
+ }
-Now we have our abstract factory that lets us make family of related objects i.e. Elven kingdom factory creates Elven castle, king and army etc.
+ @Override
+ public King createKing() {
+ return new ElfKing();
+ }
-```java
-var factory = new ElfKingdomFactory();
-var castle = factory.createCastle();
-var king = factory.createKing();
-var army = factory.createArmy();
-
-castle.getDescription(); // Output: This is the Elven castle!
-king.getDescription(); // Output: This is the Elven king!
-army.getDescription(); // Output: This is the Elven Army!
+ @Override
+ public Army createArmy() {
+ return new ElfArmy();
+ }
+}
+
+// Orcish implementations similarly -> ...
```
-Now, we can design a factory for our different kingdom factories. In this example, we created FactoryMaker, responsible for returning an instance of either ElfKingdomFactory or OrcKingdomFactory.
-The client can use FactoryMaker to create the desired concrete factory which, in turn, will produce different concrete objects (Army, King, Castle).
-In this example, we also used an enum to parameterize which type of kingdom factory the client will ask for.
+Now, we can design a factory for our different kingdom factories. In this example, we created `FactoryMaker`, responsible for returning an instance of either `ElfKingdomFactory` or `OrcKingdomFactory`. The client can use `FactoryMaker` to create the desired concrete factory which, in turn, will produce different concrete objects (derived from `Army`, `King`, `Castle`). In this example, we also used an enum to parameterize which type of kingdom factory the client will ask for.
```java
public static class FactoryMaker {
- public enum KingdomType {
- ELF, ORC
- }
-
- public static KingdomFactory makeFactory(KingdomType type) {
- switch (type) {
- case ELF:
- return new ElfKingdomFactory();
- case ORC:
- return new OrcKingdomFactory();
- default:
- throw new IllegalArgumentException("KingdomType not supported.");
+ public enum KingdomType {
+ ELF, ORC
+ }
+
+ public static KingdomFactory makeFactory(KingdomType type) {
+ return switch (type) {
+ case ELF -> new ElfKingdomFactory();
+ case ORC -> new OrcKingdomFactory();
+ };
}
- }
}
+```
-public static void main(String[] args) {
- var app = new App();
+Here is the main function of our example application:
- LOGGER.info("Elf Kingdom");
- app.createKingdom(FactoryMaker.makeFactory(KingdomType.ELF));
- LOGGER.info(app.getArmy().getDescription());
- LOGGER.info(app.getCastle().getDescription());
- LOGGER.info(app.getKing().getDescription());
+```java
+LOGGER.info("elf kingdom");
+createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+LOGGER.info(kingdom.getArmy().getDescription());
+LOGGER.info(kingdom.getCastle().getDescription());
+LOGGER.info(kingdom.getKing().getDescription());
+
+LOGGER.info("orc kingdom");
+createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+LOGGER.info(kingdom.getArmy().getDescription());
+LOGGER.info(kingdom.getCastle().getDescription());
+LOGGER.info(kingdom.getKing().getDescription());
+```
- LOGGER.info("Orc Kingdom");
- app.createKingdom(FactoryMaker.makeFactory(KingdomType.ORC));
- -- similar use of the orc factory
-}
+The program output:
+
+```
+07:35:46.340 [main] INFO com.iluwatar.abstractfactory.App -- elf kingdom
+07:35:46.343 [main] INFO com.iluwatar.abstractfactory.App -- This is the elven army!
+07:35:46.343 [main] INFO com.iluwatar.abstractfactory.App -- This is the elven castle!
+07:35:46.343 [main] INFO com.iluwatar.abstractfactory.App -- This is the elven king!
+07:35:46.343 [main] INFO com.iluwatar.abstractfactory.App -- orc kingdom
+07:35:46.343 [main] INFO com.iluwatar.abstractfactory.App -- This is the orc army!
+07:35:46.343 [main] INFO com.iluwatar.abstractfactory.App -- This is the orc castle!
+07:35:46.343 [main] INFO com.iluwatar.abstractfactory.App -- This is the orc king!
```
-## Class diagram
-
+## When to Use the Abstract Factory Pattern in Java
+Use the Abstract Factory pattern in Java when:
-## Applicability
-Use the Abstract Factory pattern when
+* The system should be independent of how its products are created, composed, and represented.
+* You need to configure the system with one of multiple families of products.
+* A family of related product objects must be used together, enforcing consistency.
+* You want to provide a class library of products, exposing only their interfaces, not their implementations.
+* The lifetime of dependencies is shorter than the consumer's lifetime.
+* Dependencies need to be constructed using runtime values or parameters.
+* You need to choose which product to use from a family at runtime.
+* Adding new products or families should not require changes to existing code.
-* a system should be independent of how its products are created, composed and represented
-* a system should be configured with one of multiple families of products
-* a family of related product objects is designed to be used together, and you need to enforce this constraint
-* you want to provide a class library of products, and you want to reveal just their interfaces, not their implementations
-* the lifetime of the dependency is conceptually shorter than the lifetime of the consumer.
-* you need a run-time value to construct a particular dependency
-* you want to decide which product to call from a family at runtime.
-* you need to supply one or more parameters only known at run-time before you can resolve a dependency.
-* when you need consistency among products
-* you don’t want to change existing code when adding new products or families of products to the program.
+## Abstract Factory Pattern Java Tutorials
-## Use Cases:
+* [Abstract Factory Design Pattern in Java (DigitalOcean)](https://www.digitalocean.com/community/tutorials/abstract-factory-design-pattern-in-java)
+* [Abstract Factory(Refactoring Guru)](https://refactoring.guru/design-patterns/abstract-factory)
-* Selecting to call the appropriate implementation of FileSystemAcmeService or DatabaseAcmeService or NetworkAcmeService at runtime.
-* Unit test case writing becomes much easier
-* UI tools for different OS
+## Benefits and Trade-offs of Abstract Factory Pattern
-## Consequences:
+Benefits:
-* Dependency injection in java hides the service class dependencies that can lead to runtime errors that would have been caught at compile time.
-* While the pattern is great when creating predefined objects, adding the new ones might be challenging.
-* The code may become more complicated than it should be, since a lot of new interfaces and classes are introduced along with the pattern.
+* Flexibility: Easily switch between product families without code modifications.
+* Decoupling: Client code only interacts with abstract interfaces, promoting portability and maintainability.
-## Tutorial
-* [Abstract Factory Pattern Tutorial](https://www.journaldev.com/1418/abstract-factory-design-pattern-in-java)
+* Reusability: Abstract factories and products facilitate component reuse across projects.
+* Maintainability: Changes to individual product families are localized, simplifying updates.
-## Real world examples
+Trade-offs:
+* Complexity: Defining abstract interfaces and concrete factories adds initial overhead.
+
+* Indirectness: Client code interacts with products indirectly through factories, potentially reducing transparency.
+
+## Real-World Applications of Abstract Factory Pattern in Java
+
+* Java Swing's `LookAndFeel` classes for providing different look-and-feel options.
+* Various implementations in the Java Abstract Window Toolkit (AWT) for creating different GUI components.
* [javax.xml.parsers.DocumentBuilderFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/parsers/DocumentBuilderFactory.html)
* [javax.xml.transform.TransformerFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/transform/TransformerFactory.html#newInstance--)
* [javax.xml.xpath.XPathFactory](http://docs.oracle.com/javase/8/docs/api/javax/xml/xpath/XPathFactory.html#newInstance--)
-## Credits
+## Related Java Design Patterns
+
+* [Factory Method](https://java-design-patterns.com/patterns/factory-method/): Abstract Factory uses Factory Methods to create products.
+* [Singleton](https://java-design-patterns.com/patterns/singleton/): Abstract Factory classes are often implemented as Singletons.
+* [Factory Kit](https://java-design-patterns.com/patterns/factory-kit/): Similar to Abstract Factory but focuses on configuring and managing a set of related objects in a flexible way.
+
+## References and Credits
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
+* [Design Patterns in Java](https://amzn.to/3Syw0vC)
+* [Head First Design Patterns: Building Extensible and Maintainable Object-Oriented Software](https://amzn.to/49NGldq)
+* [Java Design Patterns: A Hands-On Experience with Real-World Examples](https://amzn.to/3HWNf4U)
diff --git a/abstract-factory/pom.xml b/abstract-factory/pom.xml
index 614b26232d99..60fbf72eff54 100644
--- a/abstract-factory/pom.xml
+++ b/abstract-factory/pom.xml
@@ -1,56 +1,72 @@
-
-
-
- 4.0.0
-
- com.iluwatar
- java-design-patterns
- 1.23.0-SNAPSHOT
-
- abstract-factory
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
-
-
-
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+ abstract-factory
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+
+
+
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.abstractfactory.App
-
-
-
-
-
-
-
-
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.abstractfactory.App
+
+
+
+
+
+
+
+
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/App.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/App.java
index e158ece74b48..798cbe4fd118 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/App.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/App.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,10 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-import com.iluwatar.abstractfactory.App.FactoryMaker.KingdomType;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
/**
* The Abstract Factory pattern provides a way to encapsulate a group of individual factories that
@@ -39,87 +39,13 @@
*
*
The essence of the Abstract Factory pattern is a factory interface ({@link KingdomFactory})
* and its implementations ( {@link ElfKingdomFactory}, {@link OrcKingdomFactory}). The example uses
- * both concrete implementations to create a king, a castle and an army.
+ * both concrete implementations to create a king, a castle, and an army.
*/
-public class App {
-
- private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
+@Slf4j
+@Getter
+public class App implements Runnable {
- private King king;
- private Castle castle;
- private Army army;
-
- /**
- * Creates kingdom.
- */
- public void createKingdom(final KingdomFactory factory) {
- setKing(factory.createKing());
- setCastle(factory.createCastle());
- setArmy(factory.createArmy());
- }
-
- King getKing(final KingdomFactory factory) {
- return factory.createKing();
- }
-
- public King getKing() {
- return king;
- }
-
- private void setKing(final King king) {
- this.king = king;
- }
-
- Castle getCastle(final KingdomFactory factory) {
- return factory.createCastle();
- }
-
- public Castle getCastle() {
- return castle;
- }
-
- private void setCastle(final Castle castle) {
- this.castle = castle;
- }
-
- Army getArmy(final KingdomFactory factory) {
- return factory.createArmy();
- }
-
- public Army getArmy() {
- return army;
- }
-
- private void setArmy(final Army army) {
- this.army = army;
- }
-
- /**
- * The factory of kingdom factories.
- */
- public static class FactoryMaker {
-
- /**
- * Enumeration for the different types of Kingdoms.
- */
- public enum KingdomType {
- ELF, ORC
- }
-
- /**
- * The factory method to create KingdomFactory concrete objects.
- */
- public static KingdomFactory makeFactory(KingdomType type) {
- switch (type) {
- case ELF:
- return new ElfKingdomFactory();
- case ORC:
- return new OrcKingdomFactory();
- default:
- throw new IllegalArgumentException("KingdomType not supported.");
- }
- }
- }
+ private final Kingdom kingdom = new Kingdom();
/**
* Program entry point.
@@ -127,19 +53,34 @@ public static KingdomFactory makeFactory(KingdomType type) {
* @param args command line args
*/
public static void main(String[] args) {
-
var app = new App();
+ app.run();
+ }
- LOGGER.info("Elf Kingdom");
- app.createKingdom(FactoryMaker.makeFactory(KingdomType.ELF));
- LOGGER.info(app.getArmy().getDescription());
- LOGGER.info(app.getCastle().getDescription());
- LOGGER.info(app.getKing().getDescription());
+ @Override
+ public void run() {
+ LOGGER.info("elf kingdom");
+ createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+ LOGGER.info(kingdom.getArmy().getDescription());
+ LOGGER.info(kingdom.getCastle().getDescription());
+ LOGGER.info(kingdom.getKing().getDescription());
+
+ LOGGER.info("orc kingdom");
+ createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+ LOGGER.info(kingdom.getArmy().getDescription());
+ LOGGER.info(kingdom.getCastle().getDescription());
+ LOGGER.info(kingdom.getKing().getDescription());
+ }
- LOGGER.info("Orc Kingdom");
- app.createKingdom(FactoryMaker.makeFactory(KingdomType.ORC));
- LOGGER.info(app.getArmy().getDescription());
- LOGGER.info(app.getCastle().getDescription());
- LOGGER.info(app.getKing().getDescription());
+ /**
+ * Creates kingdom.
+ *
+ * @param kingdomType type of Kingdom
+ */
+ public void createKingdom(final Kingdom.FactoryMaker.KingdomType kingdomType) {
+ final KingdomFactory kingdomFactory = Kingdom.FactoryMaker.makeFactory(kingdomType);
+ kingdom.setKing(kingdomFactory.createKing());
+ kingdom.setCastle(kingdomFactory.createCastle());
+ kingdom.setArmy(kingdomFactory.createArmy());
}
-}
\ No newline at end of file
+}
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Army.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Army.java
index 51f69a82256c..78c75323f1c0 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Army.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Army.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * Army interface.
- */
+/** Army interface. */
public interface Army {
String getDescription();
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Castle.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Castle.java
index c75eb32ef333..ee1e16f3cd3f 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Castle.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Castle.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * Castle interface.
- */
+/** Castle interface. */
public interface Castle {
String getDescription();
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfArmy.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfArmy.java
index 6d2da97ccfd9..d7e46c1456f0 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfArmy.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfArmy.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * ElfArmy.
- */
+/** ElfArmy. */
public class ElfArmy implements Army {
- static final String DESCRIPTION = "This is the Elven Army!";
+ static final String DESCRIPTION = "This is the elven army!";
@Override
public String getDescription() {
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfCastle.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfCastle.java
index 5f2b6ed2a5e8..136afb11fd23 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfCastle.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfCastle.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * ElfCastle.
- */
+/** ElfCastle. */
public class ElfCastle implements Castle {
- static final String DESCRIPTION = "This is the Elven castle!";
+ static final String DESCRIPTION = "This is the elven castle!";
@Override
public String getDescription() {
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKing.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKing.java
index f7c4c614667f..9b0d3a6f1a77 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKing.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKing.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * ElfKing.
- */
+/** ElfKing. */
public class ElfKing implements King {
- static final String DESCRIPTION = "This is the Elven king!";
+ static final String DESCRIPTION = "This is the elven king!";
@Override
public String getDescription() {
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKingdomFactory.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKingdomFactory.java
index 4493d2d08a39..b09a2f47c252 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKingdomFactory.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/ElfKingdomFactory.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * ElfKingdomFactory concrete factory.
- */
+/** ElfKingdomFactory concrete factory. */
public class ElfKingdomFactory implements KingdomFactory {
@Override
@@ -42,5 +41,4 @@ public King createKing() {
public Army createArmy() {
return new ElfArmy();
}
-
}
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/King.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/King.java
index 97e5f676f29f..9f65ed434577 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/King.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/King.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * King interface.
- */
+/** King interface. */
public interface King {
String getDescription();
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Kingdom.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Kingdom.java
new file mode 100644
index 000000000000..d1f85a6a4812
--- /dev/null
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/Kingdom.java
@@ -0,0 +1,56 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.abstractfactory;
+
+import lombok.Getter;
+import lombok.Setter;
+
+/** Helper class to manufacture {@link KingdomFactory} beans. */
+@Getter
+@Setter
+public class Kingdom {
+
+ private King king;
+ private Castle castle;
+ private Army army;
+
+ /** The factory of kingdom factories. */
+ public static class FactoryMaker {
+
+ /** Enumeration for the different types of Kingdoms. */
+ public enum KingdomType {
+ ELF,
+ ORC
+ }
+
+ /** The factory method to create KingdomFactory concrete objects. */
+ public static KingdomFactory makeFactory(KingdomType type) {
+ return switch (type) {
+ case ELF -> new ElfKingdomFactory();
+ case ORC -> new OrcKingdomFactory();
+ };
+ }
+ }
+}
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/KingdomFactory.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/KingdomFactory.java
index a72dbf78cbe0..199c6697dcaa 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/KingdomFactory.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/KingdomFactory.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * KingdomFactory factory interface.
- */
+/** KingdomFactory factory interface. */
public interface KingdomFactory {
Castle createCastle();
@@ -33,5 +32,4 @@ public interface KingdomFactory {
King createKing();
Army createArmy();
-
}
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcArmy.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcArmy.java
index ae0bd5c3e24a..31ed6896d921 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcArmy.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcArmy.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * OrcArmy.
- */
+/** OrcArmy. */
public class OrcArmy implements Army {
- static final String DESCRIPTION = "This is the Orc Army!";
+ static final String DESCRIPTION = "This is the orc army!";
@Override
public String getDescription() {
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcCastle.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcCastle.java
index 458a61bf9920..bdae5709a97c 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcCastle.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcCastle.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * OrcCastle.
- */
+/** OrcCastle. */
public class OrcCastle implements Castle {
- static final String DESCRIPTION = "This is the Orc castle!";
+ static final String DESCRIPTION = "This is the orc castle!";
@Override
public String getDescription() {
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKing.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKing.java
index f73ada9b080e..7f106d45a01d 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKing.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKing.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * OrcKing.
- */
+/** OrcKing. */
public class OrcKing implements King {
- static final String DESCRIPTION = "This is the Orc king!";
+ static final String DESCRIPTION = "This is the orc king!";
@Override
public String getDescription() {
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKingdomFactory.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKingdomFactory.java
index ae7c744be72b..82d258570460 100644
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKingdomFactory.java
+++ b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/OrcKingdomFactory.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
-/**
- * OrcKingdomFactory concrete factory.
- */
+/** OrcKingdomFactory concrete factory. */
public class OrcKingdomFactory implements KingdomFactory {
@Override
diff --git a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/module-info.java b/abstract-factory/src/main/java/com/iluwatar/abstractfactory/module-info.java
deleted file mode 100644
index f075aadc0b82..000000000000
--- a/abstract-factory/src/main/java/com/iluwatar/abstractfactory/module-info.java
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-module com.iluwatar.abstractfactory {
- requires org.slf4j;
-}
\ No newline at end of file
diff --git a/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AbstractFactoryTest.java b/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AbstractFactoryTest.java
index be83cc315627..b5dde940c464 100644
--- a/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AbstractFactoryTest.java
+++ b/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AbstractFactoryTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,68 +22,71 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;
-import com.iluwatar.abstractfactory.App.FactoryMaker;
-import com.iluwatar.abstractfactory.App.FactoryMaker.KingdomType;
-import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
-/**
- * Test for abstract factory.
- */
-public class AbstractFactoryTest {
+/** Tests for abstract factory. */
+class AbstractFactoryTest {
- private App app = new App();
- private KingdomFactory elfFactory;
- private KingdomFactory orcFactory;
-
- @BeforeEach
- public void setUp() {
- elfFactory = FactoryMaker.makeFactory(KingdomType.ELF);
- orcFactory = FactoryMaker.makeFactory(KingdomType.ORC);
- }
+ private final App app = new App();
@Test
- public void king() {
- final var elfKing = app.getKing(elfFactory);
+ void verifyKingCreation() {
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+ final var kingdom = app.getKingdom();
+
+ final var elfKing = kingdom.getKing();
assertTrue(elfKing instanceof ElfKing);
assertEquals(ElfKing.DESCRIPTION, elfKing.getDescription());
- final var orcKing = app.getKing(orcFactory);
+
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+ final var orcKing = kingdom.getKing();
assertTrue(orcKing instanceof OrcKing);
assertEquals(OrcKing.DESCRIPTION, orcKing.getDescription());
}
@Test
- public void castle() {
- final var elfCastle = app.getCastle(elfFactory);
+ void verifyCastleCreation() {
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+ final var kingdom = app.getKingdom();
+
+ final var elfCastle = kingdom.getCastle();
assertTrue(elfCastle instanceof ElfCastle);
assertEquals(ElfCastle.DESCRIPTION, elfCastle.getDescription());
- final var orcCastle = app.getCastle(orcFactory);
+
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+ final var orcCastle = kingdom.getCastle();
assertTrue(orcCastle instanceof OrcCastle);
assertEquals(OrcCastle.DESCRIPTION, orcCastle.getDescription());
}
@Test
- public void army() {
- final var elfArmy = app.getArmy(elfFactory);
+ void verifyArmyCreation() {
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+ final var kingdom = app.getKingdom();
+
+ final var elfArmy = kingdom.getArmy();
assertTrue(elfArmy instanceof ElfArmy);
assertEquals(ElfArmy.DESCRIPTION, elfArmy.getDescription());
- final var orcArmy = app.getArmy(orcFactory);
+
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+ final var orcArmy = kingdom.getArmy();
assertTrue(orcArmy instanceof OrcArmy);
assertEquals(OrcArmy.DESCRIPTION, orcArmy.getDescription());
}
@Test
- public void createElfKingdom() {
- app.createKingdom(elfFactory);
- final var king = app.getKing();
- final var castle = app.getCastle();
- final var army = app.getArmy();
+ void verifyElfKingdomCreation() {
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ELF);
+ final var kingdom = app.getKingdom();
+
+ final var king = kingdom.getKing();
+ final var castle = kingdom.getCastle();
+ final var army = kingdom.getArmy();
assertTrue(king instanceof ElfKing);
assertEquals(ElfKing.DESCRIPTION, king.getDescription());
assertTrue(castle instanceof ElfCastle);
@@ -91,11 +96,13 @@ public void createElfKingdom() {
}
@Test
- public void createOrcKingdom() {
- app.createKingdom(orcFactory);
- final var king = app.getKing();
- final var castle = app.getCastle();
- final var army = app.getArmy();
+ void verifyOrcKingdomCreation() {
+ app.createKingdom(Kingdom.FactoryMaker.KingdomType.ORC);
+ final var kingdom = app.getKingdom();
+
+ final var king = kingdom.getKing();
+ final var castle = kingdom.getCastle();
+ final var army = kingdom.getArmy();
assertTrue(king instanceof OrcKing);
assertEquals(OrcKing.DESCRIPTION, king.getDescription());
assertTrue(castle instanceof OrcCastle);
diff --git a/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AppTest.java b/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AppTest.java
index 4036cc9b8e34..9f53691a594d 100644
--- a/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AppTest.java
+++ b/abstract-factory/src/test/java/com/iluwatar/abstractfactory/AppTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,17 +22,18 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.abstractfactory;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
import org.junit.jupiter.api.Test;
-/**
- * Tests that Abstract Factory example runs without errors.
- */
-public class AppTest {
+/** Check whether the execution of the main method in {@link App} throws an exception. */
+class AppTest {
+
@Test
- public void test() {
- App.main(new String[]{});
+ void shouldExecuteApplicationWithoutException() {
+
+ assertDoesNotThrow(() -> App.main(new String[] {}));
}
}
diff --git a/active-object/README.md b/active-object/README.md
new file mode 100644
index 000000000000..a804ce9e632b
--- /dev/null
+++ b/active-object/README.md
@@ -0,0 +1,222 @@
+---
+title: "Active Object Pattern in Java: Achieving Efficient Asynchronous Processing"
+shortTitle: Active Object
+description: "Learn about the Active Object design pattern in Java. This guide covers asynchronous behavior, concurrency, and practical examples to enhance your Java applications' performance."
+category: Concurrency
+language: en
+tag:
+ - Asynchronous
+ - Decoupling
+ - Messaging
+ - Synchronization
+ - Thread management
+---
+
+## Intent of Active Object Design Pattern
+
+The Active Object pattern provides a reliable method for asynchronous processing in Java, ensuring responsive applications and efficient thread management. It achieves this by encapsulating tasks within objects that have their own thread and message queue. This separation keeps the main thread responsive and avoids issues like direct thread manipulation or shared state access.
+
+## Detailed Explanation of Active Object Pattern with Real-World Examples
+
+Real-world example
+
+> Imagine a busy restaurant where customers place orders with waiters. Instead of the waiters going to the kitchen to prepare the food themselves, they write the orders on slips and hand them to a dispatcher. The dispatcher manages a pool of chefs who prepare the meals asynchronously. Once a chef is free, they pick up the next order from the queue, prepare the dish, and notify the waiter when it's ready for serving.
+>
+> In this analogy, the waiters represent the client threads, the dispatcher represents the scheduler, and the chefs represent the method execution in separate threads. This setup allows the waiters to continue taking orders without being blocked by the food preparation process, much like the Active Object pattern decouples method invocation from execution to enhance concurrency.
+
+In plain words
+
+> The Active Object pattern decouples method execution from method invocation to improve concurrency and responsiveness in multithreaded applications.
+
+Wikipedia says
+
+> The active object design pattern decouples method execution from method invocation for objects that each reside in their own thread of control.[1] The goal is to introduce concurrency, by using asynchronous method invocation and a scheduler for handling requests.
+>
+> The pattern consists of six elements:
+>
+> * A proxy, which provides an interface towards clients with publicly accessible methods.
+> * An interface which defines the method request on an active object.
+> * A list of pending requests from clients.
+> * A scheduler, which decides which request to execute next.
+> * The implementation of the active object method.
+> * A callback or variable for the client to receive the result.
+
+Sequence diagram
+
+
+
+
+## Programmatic Example of Active Object in Java
+
+This section explains how the Active Object design pattern works in Java, highlighting its use in asynchronous task management and concurrency control.
+
+The Orcs are known for their wildness and untameable soul. It seems like they have their own thread of control based on previous behavior. To implement a creature that has its own thread of control mechanism and expose its API only and not the execution itself, we can use the Active Object pattern.
+
+```java
+public abstract class ActiveCreature {
+ private final Logger logger = LoggerFactory.getLogger(ActiveCreature.class.getName());
+
+ private BlockingQueue requests;
+
+ private String name;
+
+ private Thread thread;
+
+ public ActiveCreature(String name) {
+ this.name = name;
+ this.requests = new LinkedBlockingQueue();
+ thread = new Thread(new Runnable() {
+ @Override
+ public void run() {
+ while (true) {
+ try {
+ requests.take().run();
+ } catch (InterruptedException e) {
+ logger.error(e.getMessage());
+ }
+ }
+ }
+ }
+ );
+ thread.start();
+ }
+
+ public void eat() throws InterruptedException {
+ requests.put(new Runnable() {
+ @Override
+ public void run() {
+ logger.info("{} is eating!", name());
+ logger.info("{} has finished eating!", name());
+ }
+ }
+ );
+ }
+
+ public void roam() throws InterruptedException {
+ requests.put(new Runnable() {
+ @Override
+ public void run() {
+ logger.info("{} has started to roam the wastelands.", name());
+ }
+ }
+ );
+ }
+
+ public String name() {
+ return this.name;
+ }
+}
+```
+
+We can see that any class that will extend the `ActiveCreature` class will have its own thread of control to invoke and execute methods.
+
+For example, the `Orc` class:
+
+```java
+public class Orc extends ActiveCreature {
+
+ public Orc(String name) {
+ super(name);
+ }
+}
+```
+
+Now, we can create multiple creatures such as orcs, tell them to eat and roam, and they will execute it on their own thread of control:
+
+```java
+public class App implements Runnable {
+
+ private static final Logger logger = LoggerFactory.getLogger(App.class.getName());
+
+ private static final int NUM_CREATURES = 3;
+
+ public static void main(String[] args) {
+ var app = new App();
+ app.run();
+ }
+
+ @Override
+ public void run() {
+ List creatures = new ArrayList<>();
+ try {
+ for (int i = 0; i < NUM_CREATURES; i++) {
+ creatures.add(new Orc(Orc.class.getSimpleName() + i));
+ creatures.get(i).eat();
+ creatures.get(i).roam();
+ }
+ Thread.sleep(1000);
+ } catch (InterruptedException e) {
+ logger.error(e.getMessage());
+ Thread.currentThread().interrupt();
+ } finally {
+ for (int i = 0; i < NUM_CREATURES; i++) {
+ creatures.get(i).kill(0);
+ }
+ }
+ }
+}
+```
+
+Program output:
+
+```
+09:00:02.501 [Thread-0] INFO com.iluwatar.activeobject.ActiveCreature -- Orc0 is eating!
+09:00:02.501 [Thread-2] INFO com.iluwatar.activeobject.ActiveCreature -- Orc2 is eating!
+09:00:02.501 [Thread-1] INFO com.iluwatar.activeobject.ActiveCreature -- Orc1 is eating!
+09:00:02.504 [Thread-0] INFO com.iluwatar.activeobject.ActiveCreature -- Orc0 has finished eating!
+09:00:02.504 [Thread-1] INFO com.iluwatar.activeobject.ActiveCreature -- Orc1 has finished eating!
+09:00:02.504 [Thread-0] INFO com.iluwatar.activeobject.ActiveCreature -- Orc0 has started to roam in the wastelands.
+09:00:02.504 [Thread-2] INFO com.iluwatar.activeobject.ActiveCreature -- Orc2 has finished eating!
+09:00:02.504 [Thread-1] INFO com.iluwatar.activeobject.ActiveCreature -- Orc1 has started to roam in the wastelands.
+09:00:02.504 [Thread-2] INFO com.iluwatar.activeobject.ActiveCreature -- Orc2 has started to roam in the wastelands.
+```
+
+## When to Use the Active Object Pattern in Java
+
+Use the Active Object pattern in Java when:
+
+* when you need to handle asynchronous tasks without blocking the main thread, ensuring better performance and responsiveness.
+* When you need to interact with external resources asynchronously.
+* When you want to improve the responsiveness of your application.
+* When you need to manage concurrent tasks in a modular and maintainable way.
+
+## Active Object Pattern Java Tutorials
+
+* [Android and Java Concurrency: The Active Object Pattern(Douglas Schmidt)](https://www.youtube.com/watch?v=Cd8t2u5Qmvc)
+
+## Real-World Applications of Active Object Pattern in Java
+
+* Real-time trading systems where transaction requests are handled asynchronously.
+* GUIs where long-running tasks are executed in the background without freezing the user interface.
+* Game programming to handle concurrent updates to game state or AI computations.
+
+## Benefits and Trade-offs of Active Object Pattern
+
+Discover the benefits and trade-offs of using the Active Object pattern in Java, including improved thread safety and potential overhead concerns.
+
+Benefits:
+
+* Improves responsiveness of the main thread.
+* Encapsulates concurrency concerns within objects.
+* Promotes better code organization and maintainability.
+* Provides thread safety and avoids shared state access problems.
+
+Trade-offs:
+
+* Introduces additional overhead due to message passing and thread management.
+* May not be suitable for all types of concurrency problems.
+
+## Related Java Design Patterns
+
+* [Command](https://java-design-patterns.com/patterns/command/): Encapsulates a request as an object, similarly to how the Active Object pattern encapsulates method calls.
+* [Promise](https://java-design-patterns.com/patterns/promise/): Provides a means to retrieve the result of an asynchronous method call, often used in conjunction with Active Object.
+* [Proxy](https://java-design-patterns.com/patterns/proxy/): The Active Object pattern can use a proxy to handle method invocations asynchronously.
+
+## References and Credits
+
+* [Design Patterns: Elements of Reusable Object Software](https://amzn.to/3HYqrBE)
+* [Concurrent Programming in Java: Design Principles and Patterns](https://amzn.to/498SRVq)
+* [Java Concurrency in Practice](https://amzn.to/4aRMruW)
+* [Learning Concurrent Programming in Scala](https://amzn.to/3UE07nV)
+* [Pattern Languages of Program Design 3](https://amzn.to/3OI1j61)
+* [Pattern-Oriented Software Architecture Volume 2: Patterns for Concurrent and Networked Objects](https://amzn.to/3UgC24V)
diff --git a/active-object/etc/active-object-sequence-diagram.png b/active-object/etc/active-object-sequence-diagram.png
new file mode 100644
index 000000000000..b725d9b07b6d
Binary files /dev/null and b/active-object/etc/active-object-sequence-diagram.png differ
diff --git a/active-object/etc/active-object.urm.png b/active-object/etc/active-object.urm.png
new file mode 100644
index 000000000000..c14f66144ee2
Binary files /dev/null and b/active-object/etc/active-object.urm.png differ
diff --git a/active-object/etc/active-object.urm.puml b/active-object/etc/active-object.urm.puml
new file mode 100644
index 000000000000..3fc3c8e1e921
--- /dev/null
+++ b/active-object/etc/active-object.urm.puml
@@ -0,0 +1,25 @@
+@startuml
+package com.iluwatar.activeobject {
+ abstract class ActiveCreature {
+ - logger : Logger
+ - name : String
+ - requests : BlockingQueue
+ - thread : Thread
+ + ActiveCreature(name : String)
+ + eat()
+ + name() : String
+ + roam()
+ }
+ class App {
+ - creatures : Integer
+ - logger : Logger
+ + App()
+ + main(args : String[]) {static}
+ + run()
+ }
+ class Orc {
+ + Orc(name : String)
+ }
+}
+Orc --|> ActiveCreature
+@enduml
\ No newline at end of file
diff --git a/active-object/pom.xml b/active-object/pom.xml
new file mode 100644
index 000000000000..aa26dbbe2e48
--- /dev/null
+++ b/active-object/pom.xml
@@ -0,0 +1,72 @@
+
+
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+ active-object
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.activeobject.App
+
+
+
+
+
+
+
+
+
diff --git a/active-object/src/main/java/com/iluwatar/activeobject/ActiveCreature.java b/active-object/src/main/java/com/iluwatar/activeobject/ActiveCreature.java
new file mode 100644
index 000000000000..5a440020c0ac
--- /dev/null
+++ b/active-object/src/main/java/com/iluwatar/activeobject/ActiveCreature.java
@@ -0,0 +1,118 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.activeobject;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/** ActiveCreature class is the base of the active object example. */
+public abstract class ActiveCreature {
+
+ private static final Logger logger = LoggerFactory.getLogger(ActiveCreature.class.getName());
+
+ private BlockingQueue requests;
+
+ private String name;
+
+ private Thread thread; // Thread of execution.
+
+ private int status; // status of the thread of execution.
+
+ /** Constructor and initialization. */
+ protected ActiveCreature(String name) {
+ this.name = name;
+ this.status = 0;
+ this.requests = new LinkedBlockingQueue<>();
+ thread =
+ new Thread(
+ () -> {
+ boolean infinite = true;
+ while (infinite) {
+ try {
+ requests.take().run();
+ } catch (InterruptedException e) {
+ if (this.status != 0) {
+ logger.error("Thread was interrupted. --> {}", e.getMessage());
+ }
+ infinite = false;
+ Thread.currentThread().interrupt();
+ }
+ }
+ });
+ thread.start();
+ }
+
+ /**
+ * Eats the porridge.
+ *
+ * @throws InterruptedException due to firing a new Runnable.
+ */
+ public void eat() throws InterruptedException {
+ requests.put(
+ () -> {
+ logger.info("{} is eating!", name());
+ logger.info("{} has finished eating!", name());
+ });
+ }
+
+ /**
+ * Roam the wastelands.
+ *
+ * @throws InterruptedException due to firing a new Runnable.
+ */
+ public void roam() throws InterruptedException {
+ requests.put(() -> logger.info("{} has started to roam in the wastelands.", name()));
+ }
+
+ /**
+ * Returns the name of the creature.
+ *
+ * @return the name of the creature.
+ */
+ public String name() {
+ return this.name;
+ }
+
+ /**
+ * Kills the thread of execution.
+ *
+ * @param status of the thread of execution. 0 == OK, the rest is logging an error.
+ */
+ public void kill(int status) {
+ this.status = status;
+ this.thread.interrupt();
+ }
+
+ /**
+ * Returns the status of the thread of execution.
+ *
+ * @return the status of the thread of execution.
+ */
+ public int getStatus() {
+ return this.status;
+ }
+}
diff --git a/active-object/src/main/java/com/iluwatar/activeobject/App.java b/active-object/src/main/java/com/iluwatar/activeobject/App.java
new file mode 100644
index 000000000000..ca3a5526ebb8
--- /dev/null
+++ b/active-object/src/main/java/com/iluwatar/activeobject/App.java
@@ -0,0 +1,75 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.activeobject;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * The Active Object pattern helps to solve synchronization difficulties without using
+ * 'synchronized' methods. The active object will contain a thread-safe data structure (such as
+ * BlockingQueue) and use to synchronize method calls by moving the logic of the method into an
+ * invocator(usually a Runnable) and store it in the DSA.
+ *
+ * In this example, we fire 20 threads to modify a value in the target class.
+ */
+public class App implements Runnable {
+
+ private static final Logger logger = LoggerFactory.getLogger(App.class.getName());
+
+ private static final int NUM_CREATURES = 3;
+
+ /**
+ * Program entry point.
+ *
+ * @param args command line arguments.
+ */
+ public static void main(String[] args) {
+ var app = new App();
+ app.run();
+ }
+
+ @Override
+ public void run() {
+ List creatures = new ArrayList<>();
+ try {
+ for (int i = 0; i < NUM_CREATURES; i++) {
+ creatures.add(new Orc(Orc.class.getSimpleName() + i));
+ creatures.get(i).eat();
+ creatures.get(i).roam();
+ }
+ Thread.sleep(1000);
+ } catch (InterruptedException e) {
+ logger.error(e.getMessage());
+ Thread.currentThread().interrupt();
+ } finally {
+ for (int i = 0; i < NUM_CREATURES; i++) {
+ creatures.get(i).kill(0);
+ }
+ }
+ }
+}
diff --git a/active-object/src/main/java/com/iluwatar/activeobject/Orc.java b/active-object/src/main/java/com/iluwatar/activeobject/Orc.java
new file mode 100644
index 000000000000..30adde034de5
--- /dev/null
+++ b/active-object/src/main/java/com/iluwatar/activeobject/Orc.java
@@ -0,0 +1,33 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.activeobject;
+
+/** An implementation of the ActiveCreature class. */
+public class Orc extends ActiveCreature {
+
+ public Orc(String name) {
+ super(name);
+ }
+}
diff --git a/active-object/src/test/java/com/iluwatar/activeobject/ActiveCreatureTest.java b/active-object/src/test/java/com/iluwatar/activeobject/ActiveCreatureTest.java
new file mode 100644
index 000000000000..be79e2fb5527
--- /dev/null
+++ b/active-object/src/test/java/com/iluwatar/activeobject/ActiveCreatureTest.java
@@ -0,0 +1,42 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.activeobject;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class ActiveCreatureTest {
+
+ @Test
+ void executionTest() throws InterruptedException {
+ ActiveCreature orc = new Orc("orc1");
+ assertEquals("orc1", orc.name());
+ assertEquals(0, orc.getStatus());
+ orc.eat();
+ orc.roam();
+ orc.kill(0);
+ }
+}
diff --git a/active-object/src/test/java/com/iluwatar/activeobject/AppTest.java b/active-object/src/test/java/com/iluwatar/activeobject/AppTest.java
new file mode 100644
index 000000000000..559e2a1f58f1
--- /dev/null
+++ b/active-object/src/test/java/com/iluwatar/activeobject/AppTest.java
@@ -0,0 +1,37 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.activeobject;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+import org.junit.jupiter.api.Test;
+
+class AppTest {
+
+ @Test
+ void shouldExecuteApplicationWithoutException() {
+ assertDoesNotThrow(() -> App.main(new String[] {}));
+ }
+}
diff --git a/actor-model/README.md b/actor-model/README.md
new file mode 100644
index 000000000000..be8065ffefef
--- /dev/null
+++ b/actor-model/README.md
@@ -0,0 +1,201 @@
+---
+title: "Actor Model Pattern in Java: Building Concurrent Systems with Elegance"
+shortTitle: Actor Model
+description: "Explore the Actor Model pattern in Java with real-world examples and practical implementation. Learn how to build scalable, message-driven systems using actors, messages, and asynchronous communication."
+category: Concurrency
+language: en
+tag:
+ - Concurrency
+ - Messaging
+ - Isolation
+ - Asynchronous
+ - Distributed Systems
+ - Actor Model
+---
+
+## Also Known As
+
+- Message-passing concurrency
+- Actor-based concurrency
+
+---
+
+## Intent of Actor Model Pattern
+
+The Actor Model pattern enables the construction of highly concurrent, distributed, and fault-tolerant systems by using isolated components (actors) that interact exclusively through asynchronous message passing.
+
+---
+
+## Detailed Explanation of Actor Model Pattern with Real-World Examples
+
+### 📦 Real-world Example
+
+Imagine a customer service system:
+- Each **customer support agent** is an **actor**.
+- Customers **send questions (messages)** to agents.
+- Each agent handles one request at a time and can **respond asynchronously** without interfering with other agents.
+
+---
+
+### 🧠 In Plain Words
+
+> "Actors are like independent workers that never share memory and only communicate through messages."
+
+---
+
+### 📖 Wikipedia Says
+
+> [Actor model](https://en.wikipedia.org/wiki/Actor_model) is a mathematical model of concurrent computation that treats "actors" as the universal primitives of concurrent computation.
+
+---
+
+### 🧹 Architecture Diagram
+
+
+
+---
+
+## Programmatic Example of Actor Model Pattern in Java
+
+### Actor.java
+
+```java
+public abstract class Actor implements Runnable {
+
+ @Setter @Getter private String actorId;
+ private final BlockingQueue mailbox = new LinkedBlockingQueue<>();
+ private volatile boolean active = true;
+
+
+ public void send(Message message) {
+ mailbox.add(message);
+ }
+
+ public void stop() {
+ active = false;
+ }
+
+ @Override
+ public void run() {
+
+ }
+
+ protected abstract void onReceive(Message message);
+}
+
+```
+
+### Message.java
+
+```java
+
+@AllArgsConstructor
+@Getter
+@Setter
+public class Message {
+ private final String content;
+ private final String senderId;
+}
+```
+
+### ActorSystem.java
+
+```java
+public class ActorSystem {
+ public void startActor(Actor actor) {
+ String actorId = "actor-" + idCounter.incrementAndGet(); // Generate a new and unique ID
+ actor.setActorId(actorId); // assign the actor it's ID
+ actorRegister.put(actorId, actor); // Register and save the actor with it's ID
+ executor.submit(actor); // Run the actor in a thread
+ }
+ public Actor getActorById(String actorId) {
+ return actorRegister.get(actorId); // Find by Id
+ }
+
+ public void shutdown() {
+ executor.shutdownNow(); // Stop all threads
+ }
+}
+```
+
+### App.java
+
+```java
+public class App {
+ public static void main(String[] args) {
+ ActorSystem system = new ActorSystem();
+ Actor srijan = new ExampleActor(system);
+ Actor ansh = new ExampleActor2(system);
+
+ system.startActor(srijan);
+ system.startActor(ansh);
+ ansh.send(new Message("Hello ansh", srijan.getActorId()));
+ srijan.send(new Message("Hello srijan!", ansh.getActorId()));
+
+ Thread.sleep(1000); // Give time for messages to process
+
+ srijan.stop(); // Stop the actor gracefully
+ ansh.stop();
+ system.shutdown(); // Stop the actor system
+ }
+}
+```
+
+---
+
+## When to Use the Actor Model Pattern in Java
+
+- When building **concurrent or distributed systems**
+- When you want **no shared mutable state**
+- When you need **asynchronous, message-driven communication**
+- When components should be **isolated and loosely coupled**
+
+---
+
+## Actor Model Pattern Java Tutorials
+
+- [Baeldung – Akka with Java](https://www.baeldung.com/java-akka)
+- [Vaughn Vernon – Reactive Messaging Patterns](https://vaughnvernon.co/?p=1143)
+
+---
+
+## Real-World Applications of Actor Model Pattern in Java
+
+- [Akka Framework](https://akka.io/)
+- [Erlang and Elixir concurrency](https://www.erlang.org/)
+- [Microsoft Orleans](https://learn.microsoft.com/en-us/dotnet/orleans/)
+- JVM-based game engines and simulators
+
+---
+
+## Benefits and Trade-offs of Actor Model Pattern
+
+### ✅ Benefits
+- High concurrency support
+- Easy scaling across threads or machines
+- Fault isolation and recovery
+- Message ordering within actors
+
+### ⚠️ Trade-offs
+- Harder to debug due to asynchronous behavior
+- Slight performance overhead due to message queues
+- More complex to design than simple method calls
+
+---
+
+## Related Java Design Patterns
+
+- [Command Pattern](../command)
+- [Mediator Pattern](../mediator)
+- [Event-Driven Architecture](../event-driven-architecture)
+- [Observer Pattern](../observer)
+
+---
+
+## References and Credits
+
+- *Programming Erlang*, Joe Armstrong
+- *Reactive Design Patterns*, Roland Kuhn
+- *The Actor Model in 10 Minutes*, [InfoQ Article](https://www.infoq.com/articles/actor-model/)
+- [Akka Documentation](https://doc.akka.io/docs/akka/current/index.html)
+
diff --git a/actor-model/etc/Actor_Model_UML_Class_Diagram.png b/actor-model/etc/Actor_Model_UML_Class_Diagram.png
new file mode 100644
index 000000000000..a4c34d7a75fd
Binary files /dev/null and b/actor-model/etc/Actor_Model_UML_Class_Diagram.png differ
diff --git a/actor-model/etc/actor-model.urm.puml b/actor-model/etc/actor-model.urm.puml
new file mode 100644
index 000000000000..020c1fc735a4
--- /dev/null
+++ b/actor-model/etc/actor-model.urm.puml
@@ -0,0 +1,35 @@
+@startuml actor-model
+
+title Actor Model - UML Class Diagram
+
+class ActorSystem {
+ +actorOf(actor: Actor): Actor
+ +shutdown(): void
+}
+
+class Actor {
+ -mailbox: BlockingQueue
+ -active: boolean
+ +send(message: Message): void
+ +stop(): void
+ +run(): void
+ #onReceive(message: Message): void
+}
+
+class ExampleActor {
+ +onReceive(message: Message): void
+}
+
+class Message {
+ -content: String
+ -sender: Actor
+ +getContent(): String
+ +getSender(): Actor
+}
+
+ActorSystem --> Actor : creates
+Actor <|-- ExampleActor : extends
+Actor --> Message : processes
+ExampleActor --> Message : uses
+
+@enduml
diff --git a/actor-model/pom.xml b/actor-model/pom.xml
new file mode 100644
index 000000000000..76c288829b8d
--- /dev/null
+++ b/actor-model/pom.xml
@@ -0,0 +1,114 @@
+
+
+
+
+ 4.0.0
+
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+
+ actor-model
+ Actor Model
+
+
+
+
+
+ org.junit
+ junit-bom
+ 5.11.0
+ pom
+ import
+
+
+
+
+
+
+ org.junit.jupiter
+ junit-jupiter-api
+ test
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+ org.junit.platform
+ junit-platform-launcher
+ test
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+ 3.3.0
+
+
+ jar-with-dependencies
+
+
+
+ com.iluwatar.actormodel.App
+
+
+
+
+
+ make-assembly
+ package
+
+ single
+
+
+
+
+
+
+
+
+
diff --git a/actor-model/src/main/java/com/iluwatar/actormodel/Actor.java b/actor-model/src/main/java/com/iluwatar/actormodel/Actor.java
new file mode 100644
index 000000000000..6e2aaccd1937
--- /dev/null
+++ b/actor-model/src/main/java/com/iluwatar/actormodel/Actor.java
@@ -0,0 +1,63 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.actormodel;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import lombok.Getter;
+import lombok.Setter;
+
+public abstract class Actor implements Runnable {
+
+ @Setter @Getter private String actorId;
+ private final BlockingQueue mailbox = new LinkedBlockingQueue<>();
+ private volatile boolean active =
+ true; // always read from main memory and written back to main memory,
+
+ // rather than being cached in a thread's local memory. To make it consistent to all Actors
+
+ public void send(Message message) {
+ mailbox.add(message); // Add message to queue
+ }
+
+ public void stop() {
+ active = false; // Stop the actor loop
+ }
+
+ @Override
+ public void run() {
+ while (active) {
+ try {
+ Message message = mailbox.take(); // Wait for a message
+ onReceive(message); // Process it
+ } catch (InterruptedException e) {
+ Thread.currentThread().interrupt();
+ }
+ }
+ }
+
+ // Child classes must define what to do with a message
+ protected abstract void onReceive(Message message);
+}
diff --git a/actor-model/src/main/java/com/iluwatar/actormodel/ActorSystem.java b/actor-model/src/main/java/com/iluwatar/actormodel/ActorSystem.java
new file mode 100644
index 000000000000..db7c21cb6088
--- /dev/null
+++ b/actor-model/src/main/java/com/iluwatar/actormodel/ActorSystem.java
@@ -0,0 +1,51 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.actormodel;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class ActorSystem {
+ private final ExecutorService executor = Executors.newCachedThreadPool();
+ private final ConcurrentHashMap actorRegister = new ConcurrentHashMap<>();
+ private final AtomicInteger idCounter = new AtomicInteger(0);
+
+ public void startActor(Actor actor) {
+ String actorId = "actor-" + idCounter.incrementAndGet(); // Generate a new and unique ID
+ actor.setActorId(actorId); // assign the actor it's ID
+ actorRegister.put(actorId, actor); // Register and save the actor with it's ID
+ executor.submit(actor); // Run the actor in a thread
+ }
+
+ public Actor getActorById(String actorId) {
+ return actorRegister.get(actorId); // Find by Id
+ }
+
+ public void shutdown() {
+ executor.shutdownNow(); // Stop all threads
+ }
+}
diff --git a/actor-model/src/main/java/com/iluwatar/actormodel/App.java b/actor-model/src/main/java/com/iluwatar/actormodel/App.java
new file mode 100644
index 000000000000..79fe79e48a6f
--- /dev/null
+++ b/actor-model/src/main/java/com/iluwatar/actormodel/App.java
@@ -0,0 +1,64 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * The Actor Model is a design pattern used to handle concurrency in a safe, scalable, and
+ * message-driven way.
+ *
+ * In the Actor Model: - An **Actor** is an independent unit that has its own state and behavior.
+ * - Actors **communicate only through messages** — they do not share memory. - An **ActorSystem**
+ * is responsible for creating, starting, and managing the lifecycle of actors. - Messages are
+ * delivered asynchronously, and each actor processes them one at a time.
+ *
+ *
💡 Key benefits: - No shared memory = no need for complex thread-safety - Easy to scale with
+ * many actors - Suitable for highly concurrent or distributed systems
+ *
+ *
🔍 This example demonstrates the Actor Model: - `ActorSystem` starts two actors: `srijan` and
+ * `ansh`. - `ExampleActor` and `ExampleActor2` extend the `Actor` class and override the
+ * `onReceive()` method to handle messages. - Actors communicate using `send()` to pass `Message`
+ * objects that include the message content and sender's ID. - The actors process messages
+ * **asynchronously in separate threads**, and we allow a short delay (`Thread.sleep`) to let them
+ * run. - The system is shut down gracefully at the end.
+ */
+package com.iluwatar.actormodel;
+
+public class App {
+ public static void main(String[] args) throws InterruptedException {
+ ActorSystem system = new ActorSystem();
+ Actor srijan = new ExampleActor(system);
+ Actor ansh = new ExampleActor2(system);
+
+ system.startActor(srijan);
+ system.startActor(ansh);
+ ansh.send(new Message("Hello ansh", srijan.getActorId()));
+ srijan.send(new Message("Hello srijan!", ansh.getActorId()));
+
+ Thread.sleep(1000); // Give time for messages to process
+
+ srijan.stop(); // Stop the actor gracefully
+ ansh.stop();
+ system.shutdown(); // Stop the actor system
+ }
+}
diff --git a/actor-model/src/main/java/com/iluwatar/actormodel/ExampleActor.java b/actor-model/src/main/java/com/iluwatar/actormodel/ExampleActor.java
new file mode 100644
index 000000000000..fd49325f44bd
--- /dev/null
+++ b/actor-model/src/main/java/com/iluwatar/actormodel/ExampleActor.java
@@ -0,0 +1,53 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.actormodel;
+
+import java.util.ArrayList;
+import java.util.List;
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+public class ExampleActor extends Actor {
+ private final ActorSystem actorSystem;
+ @Getter private final List receivedMessages = new ArrayList<>();
+
+ public ExampleActor(ActorSystem actorSystem) {
+ this.actorSystem = actorSystem;
+ }
+
+ // Logger log = Logger.getLogger(getClass().getName());
+
+ @Override
+ protected void onReceive(Message message) {
+ LOGGER.info(
+ "[{}]Received : {} from : [{}]", getActorId(), message.getContent(), message.getSenderId());
+ Actor sender = actorSystem.getActorById(message.getSenderId()); // sender actor id
+ // Reply of the message
+ if (sender != null && !message.getSenderId().equals(getActorId())) {
+ sender.send(new Message("I got your message ", getActorId()));
+ }
+ }
+}
diff --git a/actor-model/src/main/java/com/iluwatar/actormodel/ExampleActor2.java b/actor-model/src/main/java/com/iluwatar/actormodel/ExampleActor2.java
new file mode 100644
index 000000000000..037f96716558
--- /dev/null
+++ b/actor-model/src/main/java/com/iluwatar/actormodel/ExampleActor2.java
@@ -0,0 +1,46 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.actormodel;
+
+import java.util.ArrayList;
+import java.util.List;
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+public class ExampleActor2 extends Actor {
+ private final ActorSystem actorSystem;
+ @Getter private final List receivedMessages = new ArrayList<>();
+
+ public ExampleActor2(ActorSystem actorSystem) {
+ this.actorSystem = actorSystem;
+ }
+
+ @Override
+ protected void onReceive(Message message) {
+ receivedMessages.add(message.getContent());
+ LOGGER.info("[{}]Received : {}", getActorId(), message.getContent());
+ }
+}
diff --git a/actor-model/src/main/java/com/iluwatar/actormodel/Message.java b/actor-model/src/main/java/com/iluwatar/actormodel/Message.java
new file mode 100644
index 000000000000..03ca6e02cac0
--- /dev/null
+++ b/actor-model/src/main/java/com/iluwatar/actormodel/Message.java
@@ -0,0 +1,35 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.actormodel;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@AllArgsConstructor
+@Getter
+public class Message {
+ private final String content;
+ private final String senderId;
+}
diff --git a/actor-model/src/test/java/com/iluwatar/actor/ActorModelTest.java b/actor-model/src/test/java/com/iluwatar/actor/ActorModelTest.java
new file mode 100644
index 000000000000..a4a0dee569ab
--- /dev/null
+++ b/actor-model/src/test/java/com/iluwatar/actor/ActorModelTest.java
@@ -0,0 +1,63 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.actor;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.iluwatar.actormodel.ActorSystem;
+import com.iluwatar.actormodel.App;
+import com.iluwatar.actormodel.ExampleActor;
+import com.iluwatar.actormodel.ExampleActor2;
+import com.iluwatar.actormodel.Message;
+import org.junit.jupiter.api.Test;
+
+public class ActorModelTest {
+ @Test
+ void testMainMethod() throws InterruptedException {
+ App.main(new String[] {});
+ }
+
+ @Test
+ public void testMessagePassing() throws InterruptedException {
+ ActorSystem system = new ActorSystem();
+
+ ExampleActor srijan = new ExampleActor(system);
+ ExampleActor2 ansh = new ExampleActor2(system);
+
+ system.startActor(srijan);
+ system.startActor(ansh);
+
+ // Ansh recieves a message from Srijan
+ ansh.send(new Message("Hello ansh", srijan.getActorId()));
+
+ // Wait briefly to allow async processing
+ Thread.sleep(200);
+
+ // Check that Srijan received the message
+ assertTrue(
+ ansh.getReceivedMessages().contains("Hello ansh"),
+ "ansh should receive the message from Srijan");
+ }
+}
diff --git a/acyclic-visitor/README.md b/acyclic-visitor/README.md
index f293e4393f20..fb57d5681fd4 100644
--- a/acyclic-visitor/README.md
+++ b/acyclic-visitor/README.md
@@ -1,20 +1,150 @@
---
-layout: pattern
-title: Acyclic Visitor
-folder: acyclic-visitor
-permalink: /patterns/acyclic-visitor/
-categories: Behavioral
-tags:
- - Extensibility
+title: "Acyclic Visitor Pattern in Java: Streamlining Object Interactions"
+shortTitle: Acyclic Visitor
+description: "Learn about the Acyclic Visitor pattern in Java. This guide explains how it decouples operations from object hierarchies, providing examples and real-world applications."
+category: Behavioral
+language: en
+tag:
+ - Decoupling
+ - Extensibility
+ - Interface
+ - Object composition
---
-## Intent
-Allow new functions to be added to existing class hierarchies without affecting those hierarchies, and without creating the troublesome dependency cycles that are inherent to the GOF VISITOR Pattern.
+## Intent of Acyclic Visitor Design Pattern
-## Class diagram
-
+The Acyclic Visitor pattern in Java decouples operations from an object hierarchy, providing a flexible design for various applications.
+
+## Detailed Explanation of Acyclic Visitor Pattern with Real-World Examples
+
+Real-world example
+
+> An analogous real-world example of the Acyclic Visitor pattern in Java is a museum guide system, demonstrating the practical application of this design pattern. Imagine a museum with various exhibits like paintings, sculptures, and historical artifacts. The museum has different types of guides (audio guide, human guide, virtual reality guide) that provide information about each exhibit. Instead of modifying the exhibits every time a new guide type is introduced, each guide implements an interface to visit different exhibit types. This way, the museum can add new types of guides without altering the existing exhibits, ensuring that the system remains extensible and maintainable without forming any dependency cycles.
+
+In plain words
+
+> Acyclic Visitor allows functions to be added to existing class hierarchies without modifying the hierarchies.
+
+[WikiWikiWeb](https://wiki.c2.com/?AcyclicVisitor) says
+
+> The Acyclic Visitor pattern allows new functions to be added to existing class hierarchies without affecting those hierarchies, and without creating the dependency cycles that are inherent to the GangOfFour VisitorPattern.
+
+Sequence diagram
+
+
+
+
+## Programmatic Example of Acyclic Visitor in Java
+
+In this Java example, we have a hierarchy of modem classes illustrating the Acyclic Visitor pattern. The modems in this hierarchy need to be visited by an external algorithm based on filtering criteria (is it Unix or DOS compatible modem).
+
+Here's the `Modem` hierarchy.
+
+```java
+public abstract class Modem {
+ public abstract void accept(ModemVisitor modemVisitor);
+}
+
+public class Zoom extends Modem {
+
+ // Other properties and methods...
+
+ @Override
+ public void accept(ModemVisitor modemVisitor) {
+ if (modemVisitor instanceof ZoomVisitor) {
+ ((ZoomVisitor) modemVisitor).visit(this);
+ } else {
+ LOGGER.info("Only ZoomVisitor is allowed to visit Zoom modem");
+ }
+ }
+}
+
+public class Hayes extends Modem {
+
+ // Other properties and methods...
+
+ @Override
+ public void accept(ModemVisitor modemVisitor) {
+ if (modemVisitor instanceof HayesVisitor) {
+ ((HayesVisitor) modemVisitor).visit(this);
+ } else {
+ LOGGER.info("Only HayesVisitor is allowed to visit Hayes modem");
+ }
+ }
+}
+```
+
+Next, we introduce the `ModemVisitor` hierarchy.
+
+```java
+public interface ModemVisitor {
+}
+
+public interface HayesVisitor extends ModemVisitor {
+ void visit(Hayes hayes);
+}
+
+public interface ZoomVisitor extends ModemVisitor {
+ void visit(Zoom zoom);
+}
+
+public interface AllModemVisitor extends ZoomVisitor, HayesVisitor {
+}
+
+public class ConfigureForDosVisitor implements AllModemVisitor {
+
+ // Other properties and methods...
+
+ @Override
+ public void visit(Hayes hayes) {
+ LOGGER.info(hayes + " used with Dos configurator.");
+ }
+
+ @Override
+ public void visit(Zoom zoom) {
+ LOGGER.info(zoom + " used with Dos configurator.");
+ }
+}
+
+public class ConfigureForUnixVisitor implements ZoomVisitor {
+
+ // Other properties and methods...
+
+ @Override
+ public void visit(Zoom zoom) {
+ LOGGER.info(zoom + " used with Unix configurator.");
+ }
+}
+```
+
+Finally, here are the visitors in action.
+
+```java
+public static void main(String[] args) {
+ var conUnix = new ConfigureForUnixVisitor();
+ var conDos = new ConfigureForDosVisitor();
+
+ var zoom = new Zoom();
+ var hayes = new Hayes();
+
+ hayes.accept(conDos); // Hayes modem with Dos configurator
+ zoom.accept(conDos); // Zoom modem with Dos configurator
+ hayes.accept(conUnix); // Hayes modem with Unix configurator
+ zoom.accept(conUnix); // Zoom modem with Unix configurator
+}
+```
+
+Program output:
+
+```
+09:15:11.125 [main] INFO com.iluwatar.acyclicvisitor.ConfigureForDosVisitor -- Hayes modem used with Dos configurator.
+09:15:11.127 [main] INFO com.iluwatar.acyclicvisitor.ConfigureForDosVisitor -- Zoom modem used with Dos configurator.
+09:15:11.127 [main] INFO com.iluwatar.acyclicvisitor.Hayes -- Only HayesVisitor is allowed to visit Hayes modem
+09:15:11.127 [main] INFO com.iluwatar.acyclicvisitor.ConfigureForUnixVisitor -- Zoom modem used with Unix configurator.
+```
+
+## When to Use the Acyclic Visitor Pattern in Java
-## Applicability
This pattern can be used:
* When you need to add a new function to an existing hierarchy without the need to alter or affect that hierarchy.
@@ -23,20 +153,34 @@ This pattern can be used:
* When the visited class hierarchy will be frequently extended with new derivatives of the Element class.
* When the recompilation, relinking, retesting or redistribution of the derivatives of Element is very expensive.
-## Consequences
-The good:
+## Acyclic Visitor Pattern Java Tutorials
+
+* [The Acyclic Visitor Pattern (Code Crafter)](https://codecrafter.blogspot.com/2012/12/the-acyclic-visitor-pattern.html)
+
+## Benefits and Trade-offs of Acyclic Visitor Pattern
+
+Benefits:
+
+* Extensible: New operations can be added easily without changing the object structure.
+* Decoupled: Reduces coupling between the objects and the operations on them.
+* No dependency cycles: Ensures acyclic dependencies, improving maintainability and reducing complexity.
+
+Trade-offs:
-* No dependency cycles between class hierarchies.
-* No need to recompile all the visitors if a new one is added.
-* Does not cause compilation failure in existing visitors if class hierarchy has a new member.
+* Increased complexity: Can introduce additional complexity with the need for multiple visitor interfaces.
+* Maintenance overhead: Modifying the object hierarchy requires updating all visitors.
-The bad:
+## Related Java Design Patterns
-* Violates the principle of least surprise or Liskov's Substitution principle by showing that it can accept all visitors but actually only being interested in particular visitors.
-* Parallel hierarchy of visitors has to be created for all members in visitable class hierarchy.
+* [Composite](https://java-design-patterns.com/patterns/composite/): Often used in conjunction with Acyclic Visitor to allow treating individual objects and compositions uniformly.
+* [Decorator](https://java-design-patterns.com/patterns/decorator/): Can be used alongside to add responsibilities to objects dynamically.
+* [Visitor](https://java-design-patterns.com/patterns/visitor/): The Acyclic Visitor pattern is a variation of the Visitor pattern that avoids cyclic dependencies.
-## Related patterns
-* [Visitor Pattern](../visitor/)
+## References and Credits
-## Credits
-* [Acyclic Visitor](http://condor.depaul.edu/dmumaugh/OOT/Design-Principles/acv.pdf)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
+* [Head First Design Patterns: Building Extensible and Maintainable Object-Oriented Software](https://amzn.to/49NGldq)
+* [Java Design Patterns: A Hands-On Experience with Real-World Examples](https://amzn.to/3yhh525)
+* [Patterns in Java: A Catalog of Reusable Design Patterns Illustrated with UML](https://amzn.to/4bOtzwF)
+* [Acyclic Visitor (Robert C. Martin)](http://condor.depaul.edu/dmumaugh/OOT/Design-Principles/acv.pdf)
+* [Acyclic Visitor (WikiWikiWeb)](https://wiki.c2.com/?AcyclicVisitor)
diff --git a/acyclic-visitor/etc/Acyclic Visitor.ucls b/acyclic-visitor/etc/Acyclic Visitor.ucls
deleted file mode 100644
index 03b6c77dd120..000000000000
--- a/acyclic-visitor/etc/Acyclic Visitor.ucls
+++ /dev/null
@@ -1,115 +0,0 @@
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
\ No newline at end of file
diff --git a/acyclic-visitor/etc/acyclic-visitor-sequence-diagram.png b/acyclic-visitor/etc/acyclic-visitor-sequence-diagram.png
new file mode 100644
index 000000000000..a3c2ba56b89f
Binary files /dev/null and b/acyclic-visitor/etc/acyclic-visitor-sequence-diagram.png differ
diff --git a/acyclic-visitor/etc/acyclic-visitor.png b/acyclic-visitor/etc/acyclic-visitor.png
index 636532c4d5d6..7b4df13d80f8 100644
Binary files a/acyclic-visitor/etc/acyclic-visitor.png and b/acyclic-visitor/etc/acyclic-visitor.png differ
diff --git a/acyclic-visitor/pom.xml b/acyclic-visitor/pom.xml
index 24bab933a059..b4f5646b71c0 100644
--- a/acyclic-visitor/pom.xml
+++ b/acyclic-visitor/pom.xml
@@ -1,65 +1,59 @@
-
-
- 4.0.0
+
+
-
- org.assertj
- assertj-core
- 3.9.1
- test
-
-
-
- uk.org.lidalia
- slf4j-test
- 1.2.0
- test
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
- org.mockito
- mockito-all
- 1.10.19
- test
-
-
-
+ The above copyright notice and this permission notice shall be included in
+ all copies or substantial portions of the Software.
+
+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ THE SOFTWARE.
+
+-->
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+ acyclic-visitor
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+ org.mockito
+ mockito-core
+ test
+
+
+
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/AllModemVisitor.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/AllModemVisitor.java
index 354c4db74962..a3b1679a2d9f 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/AllModemVisitor.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/AllModemVisitor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,13 +22,10 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
/**
* All ModemVisitor interface extends all visitor interfaces. This interface provides ease of use
* when a visitor needs to visit all modem types.
*/
-public interface AllModemVisitor extends ZoomVisitor, HayesVisitor {
-
-}
+public interface AllModemVisitor extends ZoomVisitor, HayesVisitor {}
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/App.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/App.java
index 866abc3b736a..3b7c6cd61e4b 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/App.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/App.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
/**
@@ -36,9 +37,7 @@
*/
public class App {
- /**
- * Program's entry point.
- */
+ /** Program's entry point. */
public static void main(String[] args) {
var conUnix = new ConfigureForUnixVisitor();
var conDos = new ConfigureForDosVisitor();
@@ -49,6 +48,6 @@ public static void main(String[] args) {
hayes.accept(conDos); // Hayes modem with Dos configurator
zoom.accept(conDos); // Zoom modem with Dos configurator
hayes.accept(conUnix); // Hayes modem with Unix configurator
- zoom.accept(conUnix); // Zoom modem with Unix configurator
+ zoom.accept(conUnix); // Zoom modem with Unix configurator
}
}
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitor.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitor.java
index f9df385295d3..267a8d66ac45 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitor.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,20 +22,16 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
/**
- * ConfigureForDosVisitor class implements both zoom's and hayes' visit method for Dos
- * manufacturer.
+ * ConfigureForDosVisitor class implements both zoom's and hayes' visit method for Dos manufacturer.
*/
+@Slf4j
public class ConfigureForDosVisitor implements AllModemVisitor {
- private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForDosVisitor.class);
-
@Override
public void visit(Hayes hayes) {
LOGGER.info(hayes + " used with Dos configurator.");
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitor.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitor.java
index 3d14eff8fcee..d9fd14f69435 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitor.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,22 +22,19 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
/**
* ConfigureForUnixVisitor class implements zoom's visit method for Unix manufacturer, unlike
* traditional visitor pattern, this class may selectively implement visit for other modems.
*/
+@Slf4j
public class ConfigureForUnixVisitor implements ZoomVisitor {
- private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForUnixVisitor.class);
-
@Override
public void visit(Zoom zoom) {
LOGGER.info(zoom + " used with Unix configurator.");
}
-}
\ No newline at end of file
+}
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Hayes.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Hayes.java
index b49a6234cfd6..e0b2fcc2b530 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Hayes.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Hayes.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,22 +22,15 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
-/**
- * Hayes class implements its accept method.
- */
-public class Hayes extends Modem {
+/** Hayes class implements its accept method. */
+@Slf4j
+public class Hayes implements Modem {
- private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForDosVisitor.class);
-
- /**
- * Accepts all visitors but honors only HayesVisitor.
- */
+ /** Accepts all visitors but honors only HayesVisitor. */
@Override
public void accept(ModemVisitor modemVisitor) {
if (modemVisitor instanceof HayesVisitor) {
@@ -43,12 +38,9 @@ public void accept(ModemVisitor modemVisitor) {
} else {
LOGGER.info("Only HayesVisitor is allowed to visit Hayes modem");
}
-
}
- /**
- * Hayes' modem's toString method.
- */
+ /** Hayes' modem's toString method. */
@Override
public String toString() {
return "Hayes modem";
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/HayesVisitor.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/HayesVisitor.java
index 59527d57b2ce..aad9b970994f 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/HayesVisitor.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/HayesVisitor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-/**
- * HayesVisitor interface.
- */
+/** HayesVisitor interface. */
public interface HayesVisitor extends ModemVisitor {
void visit(Hayes hayes);
}
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Modem.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Modem.java
index 201712dd1398..8552574453e5 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Modem.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Modem.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-/**
- * Modem abstract class.
- */
-public abstract class Modem {
- public abstract void accept(ModemVisitor modemVisitor);
+/** //Modem abstract class. converted to an interface */
+public interface Modem {
+ void accept(ModemVisitor modemVisitor);
}
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ModemVisitor.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ModemVisitor.java
index b4058f237d22..9391a980cd29 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ModemVisitor.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ModemVisitor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
/**
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Zoom.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Zoom.java
index 3fbaa38dfce6..59b50a54a12f 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Zoom.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/Zoom.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,22 +22,15 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * Zoom class implements its accept method.
- */
-public class Zoom extends Modem {
+import lombok.extern.slf4j.Slf4j;
- private static final Logger LOGGER = LoggerFactory.getLogger(ConfigureForDosVisitor.class);
+/** Zoom class implements its accept method. */
+@Slf4j
+public class Zoom implements Modem {
- /**
- * Accepts all visitors but honors only ZoomVisitor.
- */
+ /** Accepts all visitors but honors only ZoomVisitor. */
@Override
public void accept(ModemVisitor modemVisitor) {
if (modemVisitor instanceof ZoomVisitor) {
@@ -45,9 +40,7 @@ public void accept(ModemVisitor modemVisitor) {
}
}
- /**
- * Zoom modem's toString method.
- */
+ /** Zoom modem's toString method. */
@Override
public String toString() {
return "Zoom modem";
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ZoomVisitor.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ZoomVisitor.java
index fd54d8b21ca7..5388ded6f735 100644
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ZoomVisitor.java
+++ b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/ZoomVisitor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-/**
- * ZoomVisitor interface.
- */
+/** ZoomVisitor interface. */
public interface ZoomVisitor extends ModemVisitor {
void visit(Zoom zoom);
}
diff --git a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/module-info.java b/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/module-info.java
deleted file mode 100644
index 78de5a786d71..000000000000
--- a/acyclic-visitor/src/main/java/com/iluwatar/acyclicvisitor/module-info.java
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-module com.iluwatar.acyclicvisitor {
- requires org.slf4j;
-}
\ No newline at end of file
diff --git a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/AppTest.java b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/AppTest.java
index 4b9a7ec6c1f7..7a21498a63ea 100644
--- a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/AppTest.java
+++ b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/AppTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,18 +22,24 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
import org.junit.jupiter.api.Test;
-/**
- * Tests that the Acyclic Visitor example runs without errors.
- */
-public class AppTest {
+/** Tests that the Acyclic Visitor example runs without errors. */
+class AppTest {
+ /**
+ * Issue: Add at least one assertion to this test case.
+ *
+ * Solution: Inserted assertion to check whether the execution of the main method in {@link
+ * App} throws an exception.
+ */
@Test
- public void test() {
- App.main(new String[]{});
+ void shouldExecuteApplicationWithoutException() {
+
+ assertDoesNotThrow(() -> App.main(new String[] {}));
}
-}
\ No newline at end of file
+}
diff --git a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitorTest.java b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitorTest.java
deleted file mode 100644
index 8847a131e605..000000000000
--- a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForDosVisitorTest.java
+++ /dev/null
@@ -1,70 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.acyclicvisitor;
-
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.groups.Tuple.tuple;
-import static uk.org.lidalia.slf4jext.Level.INFO;
-
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.Test;
-import uk.org.lidalia.slf4jtest.TestLogger;
-import uk.org.lidalia.slf4jtest.TestLoggerFactory;
-
-/**
- * ConfigureForDosVisitor test class
- */
-public class ConfigureForDosVisitorTest {
-
- private TestLogger logger = TestLoggerFactory.getTestLogger(ConfigureForDosVisitor.class);
-
- @Test
- public void testVisitForZoom() {
- var conDos = new ConfigureForDosVisitor();
- var zoom = new Zoom();
-
- conDos.visit(zoom);
-
- assertThat(logger.getLoggingEvents())
- .extracting("level", "message")
- .contains(tuple(INFO, zoom + " used with Dos configurator."));
- }
-
- @Test
- public void testVisitForHayes() {
- var conDos = new ConfigureForDosVisitor();
- var hayes = new Hayes();
-
- conDos.visit(hayes);
-
- assertThat(logger.getLoggingEvents())
- .extracting("level", "message")
- .contains(tuple(INFO, hayes + " used with Dos configurator."));
- }
-
- @AfterEach
- public void clearLoggers() {
- TestLoggerFactory.clear();
- }
-}
diff --git a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitorTest.java b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitorTest.java
deleted file mode 100644
index 32067ad385a3..000000000000
--- a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ConfigureForUnixVisitorTest.java
+++ /dev/null
@@ -1,59 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.acyclicvisitor;
-
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.groups.Tuple.tuple;
-import static uk.org.lidalia.slf4jext.Level.INFO;
-
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.Test;
-
-import uk.org.lidalia.slf4jtest.TestLogger;
-import uk.org.lidalia.slf4jtest.TestLoggerFactory;
-
-/**
- * ConfigureForUnixVisitor test class
- */
-public class ConfigureForUnixVisitorTest {
-
- private static final TestLogger LOGGER = TestLoggerFactory.getTestLogger(ConfigureForUnixVisitor.class);
-
- @AfterEach
- public void clearLoggers() {
- TestLoggerFactory.clear();
- }
-
- @Test
- public void testVisitForZoom() {
- var conUnix = new ConfigureForUnixVisitor();
- var zoom = new Zoom();
-
- conUnix.visit(zoom);
-
- assertThat(LOGGER.getLoggingEvents())
- .extracting("level", "message")
- .contains(tuple(INFO, zoom + " used with Unix configurator."));
- }
-}
diff --git a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/HayesTest.java b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/HayesTest.java
index 308dd5879329..a989d9287921 100644
--- a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/HayesTest.java
+++ b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/HayesTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,37 +22,32 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-import static org.mockito.Matchers.eq;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.verifyZeroInteractions;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.*;
import org.junit.jupiter.api.Test;
-/**
- * Hayes test class
- */
-public class HayesTest {
+/** Hayes test class */
+class HayesTest {
@Test
- public void testAcceptForDos() {
+ void testAcceptForDos() {
var hayes = new Hayes();
var mockVisitor = mock(ConfigureForDosVisitor.class);
-
+
hayes.accept(mockVisitor);
- verify((HayesVisitor)mockVisitor).visit(eq(hayes));
+ verify((HayesVisitor) mockVisitor).visit(eq(hayes));
}
-
+
@Test
- public void testAcceptForUnix() {
+ void testAcceptForUnix() {
var hayes = new Hayes();
var mockVisitor = mock(ConfigureForUnixVisitor.class);
-
+
hayes.accept(mockVisitor);
-
- verifyZeroInteractions(mockVisitor);
+
+ verifyNoMoreInteractions(mockVisitor);
}
}
diff --git a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ZoomTest.java b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ZoomTest.java
index 2dcfcfbbbf80..d5fe79965d47 100644
--- a/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ZoomTest.java
+++ b/acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/ZoomTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,36 +22,32 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.acyclicvisitor;
-
-import static org.mockito.Matchers.eq;
-import static org.mockito.Mockito.verify;
+import static org.mockito.ArgumentMatchers.eq;
import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
import org.junit.jupiter.api.Test;
-/**
- * Zoom test class
- */
-public class ZoomTest {
-
+/** Zoom test class */
+class ZoomTest {
+
@Test
- public void testAcceptForDos() {
+ void testAcceptForDos() {
var zoom = new Zoom();
var mockVisitor = mock(ConfigureForDosVisitor.class);
-
+
zoom.accept(mockVisitor);
- verify((ZoomVisitor)mockVisitor).visit(eq(zoom));
+ verify((ZoomVisitor) mockVisitor).visit(eq(zoom));
}
-
+
@Test
- public void testAcceptForUnix() {
+ void testAcceptForUnix() {
var zoom = new Zoom();
var mockVisitor = mock(ConfigureForUnixVisitor.class);
-
+
zoom.accept(mockVisitor);
- verify((ZoomVisitor)mockVisitor).visit(eq(zoom));
+ verify((ZoomVisitor) mockVisitor).visit(eq(zoom));
}
}
diff --git a/adapter/README.md b/adapter/README.md
index a8a0214be83c..489742494709 100644
--- a/adapter/README.md
+++ b/adapter/README.md
@@ -1,28 +1,31 @@
---
-layout: pattern
-title: Adapter
-folder: adapter
-permalink: /patterns/adapter/
-categories: Structural
-tags:
- - Gang of Four
+title: "Adapter Pattern in Java: Seamless Integration of Incompatible Systems"
+shortTitle: Adapter
+description: "Learn how the Adapter Design Pattern works in Java with detailed examples and use cases. Understand how it enables compatibility between incompatible interfaces."
+category: Structural
+language: en
+tag:
+ - Compatibility
+ - Decoupling
+ - Gang of Four
+ - Interface
+ - Object composition
+ - Wrapping
---
## Also known as
-Wrapper
-## Intent
-Convert the interface of a class into another interface the clients
-expect. Adapter lets classes work together that couldn't otherwise because of
-incompatible interfaces.
+* Wrapper
-## Explanation
+## Intent of Adapter Design Pattern
-Real world example
+The Adapter Design Pattern in Java converts the interface of a class into another interface that clients expect, enabling compatibility.
-> Consider that you have some pictures in your memory card and you need to transfer them to your computer. In order to transfer them you need some kind of adapter that is compatible with your computer ports so that you can attach memory card to your computer. In this case card reader is an adapter.
-> Another example would be the famous power adapter; a three legged plug can't be connected to a two pronged outlet, it needs to use a power adapter that makes it compatible with the two pronged outlet.
-> Yet another example would be a translator translating words spoken by one person to another
+## Detailed Explanation of Adapter Pattern with Real-World Examples
+
+Real-world example
+
+> Consider that you have some pictures on your memory card and you need to transfer them to your computer. To transfer them, you need some kind of adapter that is compatible with your computer ports so that you can attach a memory card to your computer. In this case card reader is an adapter. Another example would be the famous power adapter; a three-legged plug can't be connected to a two-pronged outlet, it needs to use a power adapter that makes it compatible with the two-pronged outlets. Yet another example would be a translator translating words spoken by one person to another
In plain words
@@ -32,102 +35,120 @@ Wikipedia says
> In software engineering, the adapter pattern is a software design pattern that allows the interface of an existing class to be used as another interface. It is often used to make existing classes work with others without modifying their source code.
-**Programmatic Example**
+Sequence diagram
+
+
+
+## Programmatic Example of Adapter Pattern in Java
-Consider a captain that can only use rowing boats and cannot sail at all.
+The Adapter Pattern example in Java shows how a class with an incompatible interface can be adapted to work with another class.
-First we have interfaces `RowingBoat` and `FishingBoat`
+Consider a wannabe captain that can only use rowing boats but can't sail at all.
+
+First, we have interfaces `RowingBoat` and `FishingBoat`
```java
public interface RowingBoat {
- void row();
+ void row();
}
+@Slf4j
public class FishingBoat {
- private static final Logger LOGGER = LoggerFactory.getLogger(FishingBoat.class);
- public void sail() {
- LOGGER.info("The fishing boat is sailing");
- }
+ public void sail() {
+ LOGGER.info("The fishing boat is sailing");
+ }
}
```
-And captain expects an implementation of `RowingBoat` interface to be able to move
+The captain expects an implementation of `RowingBoat` interface to be able to move.
```java
public class Captain {
- private RowingBoat rowingBoat;
- // default constructor and setter for rowingBoat
- public Captain(RowingBoat rowingBoat) {
- this.rowingBoat = rowingBoat;
- }
+ private final RowingBoat rowingBoat;
+
+ // default constructor and setter for rowingBoat
+ public Captain(RowingBoat rowingBoat) {
+ this.rowingBoat = rowingBoat;
+ }
- public void row() {
- rowingBoat.row();
- }
+ public void row() {
+ rowingBoat.row();
+ }
}
```
-Now let's say the pirates are coming and our captain needs to escape but there is only fishing boat available. We need to create an adapter that allows the captain to operate the fishing boat with his rowing boat skills.
+Now, let's say the pirates are coming and our captain needs to escape but there is only a fishing boat available. We need to create an adapter that allows the captain to operate the fishing boat with his rowing boat skills.
```java
+@Slf4j
public class FishingBoatAdapter implements RowingBoat {
- private static final Logger LOGGER = LoggerFactory.getLogger(FishingBoatAdapter.class);
-
- private FishingBoat boat;
+ private final FishingBoat boat;
- public FishingBoatAdapter() {
- boat = new FishingBoat();
- }
+ public FishingBoatAdapter() {
+ boat = new FishingBoat();
+ }
- @Override
- public void row() {
- boat.sail();
- }
+ @Override
+ public void row() {
+ boat.sail();
+ }
}
```
-And now the `Captain` can use the `FishingBoat` to escape the pirates.
+Now the `Captain` can use the `FishingBoat` to escape the pirates.
```java
-var captain = new Captain(new FishingBoatAdapter());
-captain.row();
+ public static void main(final String[] args) {
+ // The captain can only operate rowing boats but with adapter he is able to
+ // use fishing boats as well
+ var captain = new Captain(new FishingBoatAdapter());
+ captain.row();
+}
+```
+
+The program outputs:
+
+```
+10:25:08.074 [main] INFO com.iluwatar.adapter.FishingBoat -- The fishing boat is sailing
```
-## Class diagram
-
+## When to Use the Adapter Pattern in Java
-## Applicability
-Use the Adapter pattern when
+Use the Adapter pattern in Java when
-* you want to use an existing class, and its interface does not match the one you need
-* you want to create a reusable class that cooperates with unrelated or unforeseen classes, that is, classes that don't necessarily have compatible interfaces
-* you need to use several existing subclasses, but it's impractical to adapt their interface by subclassing every one. An object adapter can adapt the interface of its parent class.
-* most of the applications using third party libraries use adapters as a middle layer between the application and the 3rd party library to decouple the application from the library. If another library has to be used only an adapter for the new library is required without having to change the application code.
+* You want to use an existing class, and its interface does not match the one you need
+* You want to create a reusable class that cooperates with unrelated or unforeseen classes, that is, classes that don't necessarily have compatible interfaces
+* You need to use several existing subclasses, but it's impractical to adapt their interface by subclassing everyone. An object adapter can adapt the interface of its parent class.
+* Most of the applications using third-party libraries use adapters as a middle layer between the application and the 3rd party library to decouple the application from the library. If another library has to be used only an adapter for the new library is required without having to change the application code.
-## Consequences:
-Class and object adapters have different trade-offs. A class adapter
+## Adapter Pattern Java Tutorials
-* adapts Adaptee to Target by committing to a concrete Adaptee class. As a consequence, a class adapter won’t work when we want to adapt a class and all its subclasses.
-* let’s Adapter override some of Adaptee’s behavior, since Adapter is a subclass of Adaptee.
-* introduces only one object, and no additional pointer indirection is needed to get to the adaptee.
+* [Using the Adapter Design Pattern in Java (Dzone)](https://dzone.com/articles/adapter-design-pattern-in-java)
+* [Adapter in Java (Refactoring Guru)](https://refactoring.guru/design-patterns/adapter/java/example)
+* [The Adapter Pattern in Java (Baeldung)](https://www.baeldung.com/java-adapter-pattern)
+* [Adapter Design Pattern (GeeksForGeeks)](https://www.geeksforgeeks.org/adapter-pattern/)
-An object adapter
+## Benefits and Trade-offs of Adapter Pattern
-* let’s a single Adapter work with many Adaptees—that is, the Adaptee itself and all of its subclasses (if any). The Adapter can also add functionality to all Adaptees at once.
-* makes it harder to override Adaptee behavior. It will require subclassing Adaptee and making Adapter refer to the subclass rather than the Adaptee itself.
+Class and object adapters offer different benefits and drawbacks. A class adapter adapts the Adaptee to the Target by binding to a specific Adaptee class, which means it cannot adapt a class and all its subclasses. This type of adapter allows the Adapter to override some of the Adaptee’s behavior because the Adapter is a subclass of the Adaptee. Additionally, it introduces only one object without needing extra pointer indirection to reach the Adaptee.
+On the other hand, an object adapter allows a single Adapter to work with multiple Adaptees, including the Adaptee and all its subclasses. This type of adapter can add functionality to all Adaptees simultaneously. However, it makes overriding the Adaptee’s behavior more difficult, as it requires subclassing the Adaptee and having the Adapter refer to this subclass instead of the Adaptee itself.
-## Real world examples
+## Real-World Applications of Adapter Pattern in Java
+* `java.io.InputStreamReader` and `java.io.OutputStreamWriter` in the Java IO library.
+* GUI component libraries that allow for plug-ins or adapters to convert between different GUI component interfaces.
* [java.util.Arrays#asList()](http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#asList%28T...%29)
* [java.util.Collections#list()](https://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#list-java.util.Enumeration-)
* [java.util.Collections#enumeration()](https://docs.oracle.com/javase/8/docs/api/java/util/Collections.html#enumeration-java.util.Collection-)
* [javax.xml.bind.annotation.adapters.XMLAdapter](http://docs.oracle.com/javase/8/docs/api/javax/xml/bind/annotation/adapters/XmlAdapter.html#marshal-BoundType-)
+## References and Credits
-## Credits
-
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
-* [J2EE Design Patterns](http://www.amazon.com/J2EE-Design-Patterns-William-Crawford/dp/0596004273/ref=sr_1_2)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
+* [Effective Java](https://amzn.to/4cGk2Jz)
+* [Head First Design Patterns: Building Extensible and Maintainable Object-Oriented Software](https://amzn.to/49NGldq)
+* [J2EE Design Patterns](https://amzn.to/4dpzgmx)
+* [Refactoring to Patterns](https://amzn.to/3VOO4F5)
diff --git a/adapter/etc/adapter-sequence-diagram.png b/adapter/etc/adapter-sequence-diagram.png
new file mode 100644
index 000000000000..a9bb557ea61e
Binary files /dev/null and b/adapter/etc/adapter-sequence-diagram.png differ
diff --git a/adapter/pom.xml b/adapter/pom.xml
index 4c725def8953..6e7f45a515b5 100644
--- a/adapter/pom.xml
+++ b/adapter/pom.xml
@@ -1,61 +1,77 @@
-
-
-
- 4.0.0
-
- com.iluwatar
- java-design-patterns
- 1.23.0-SNAPSHOT
-
- adapter
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
- org.mockito
- mockito-core
- test
-
-
-
-
-
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+ adapter
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+ org.mockito
+ mockito-core
+ test
+
+
+
+
+
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.adapter.App
-
-
-
-
-
-
-
-
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.adapter.App
+
+
+
+
+
+
+
+
diff --git a/adapter/src/main/java/com/iluwatar/adapter/App.java b/adapter/src/main/java/com/iluwatar/adapter/App.java
index 4e3755fb27f2..a4fa74274f74 100644
--- a/adapter/src/main/java/com/iluwatar/adapter/App.java
+++ b/adapter/src/main/java/com/iluwatar/adapter/App.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.adapter;
/**
@@ -36,16 +37,15 @@
*
The Adapter ({@link FishingBoatAdapter}) converts the interface of the adaptee class ({@link
* FishingBoat}) into a suitable one expected by the client ({@link RowingBoat}).
*
- *
The story of this implementation is this.
The story of this implementation is this. beans;
@@ -42,11 +41,9 @@ public class AdapterPatternTest {
private static final String ROWING_BEAN = "captain";
- /**
- * This method runs before the test execution and sets the bean objects in the beans Map.
- */
+ /** This method runs before the test execution and sets the bean objects in the beans Map. */
@BeforeEach
- public void setup() {
+ void setup() {
beans = new HashMap<>();
var fishingBoatAdapter = spy(new FishingBoatAdapter());
@@ -64,7 +61,7 @@ public void setup() {
* by the client ({@link Captain} ).
*/
@Test
- public void testAdapter() {
+ void testAdapter() {
var captain = (Captain) beans.get(ROWING_BEAN);
// when captain moves
diff --git a/adapter/src/test/java/com/iluwatar/adapter/AppTest.java b/adapter/src/test/java/com/iluwatar/adapter/AppTest.java
index 3bf8e1010a11..a2cc4c22bcaa 100644
--- a/adapter/src/test/java/com/iluwatar/adapter/AppTest.java
+++ b/adapter/src/test/java/com/iluwatar/adapter/AppTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,17 +22,19 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.adapter;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
import org.junit.jupiter.api.Test;
-/**
- * Tests that Adapter example runs without errors.
- */
-public class AppTest {
+/** Tests that Adapter example runs without errors. */
+class AppTest {
+
+ /** Check whether the execution of the main method in {@link App} throws an exception. */
@Test
- public void test() {
- App.main(new String[]{});
+ void shouldExecuteApplicationWithoutException() {
+
+ assertDoesNotThrow(() -> App.main(new String[] {}));
}
}
diff --git a/aggregator-microservices/README.md b/aggregator-microservices/README.md
deleted file mode 100644
index 74a411fc5cfb..000000000000
--- a/aggregator-microservices/README.md
+++ /dev/null
@@ -1,30 +0,0 @@
----
-layout: pattern
-title: Aggregator Microservices
-folder: aggregator-microservices
-permalink: /patterns/aggregator-microservices/
-categories: Architectural
-tags:
-- Cloud distributed
----
-
-## Intent
-
-The user makes a single call to the Aggregator, and the aggregator then calls each relevant microservice and collects
-the data, apply business logic to it, and further publish is as a REST Endpoint.
-More variations of the aggregator are:
-- Proxy Microservice Design Pattern: A different microservice is called upon the business need.
-- Chained Microservice Design Pattern: In this case each microservice is dependent/ chained to a series
-of other microservices.
-
-## Class diagram
-
-
-
-## Applicability
-
-Use the Aggregator Microservices pattern when you need a unified API for various microservices, regardless the client device.
-
-## Credits
-
-* [Microservice Design Patterns](http://web.archive.org/web/20190705163602/http://blog.arungupta.me/microservice-design-patterns/)
diff --git a/aggregator-microservices/aggregator-service/pom.xml b/aggregator-microservices/aggregator-service/pom.xml
deleted file mode 100644
index f4482d0e3f8b..000000000000
--- a/aggregator-microservices/aggregator-service/pom.xml
+++ /dev/null
@@ -1,81 +0,0 @@
-
-
-
-
- aggregator-microservices
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
- aggregator-service
- jar
-
-
- org.springframework
- spring-webmvc
-
-
- org.springframework.boot
- spring-boot-starter-web
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
- org.mockito
- mockito-core
- test
-
-
-
-
-
-
- org.springframework.boot
- spring-boot-maven-plugin
-
-
-
- repackage
-
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.aggregator.microservices.App
-
-
-
-
-
-
-
-
-
diff --git a/aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/App.java b/aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/App.java
deleted file mode 100644
index 3c09c54be3b4..000000000000
--- a/aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/App.java
+++ /dev/null
@@ -1,43 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.aggregator.microservices;
-
-import org.springframework.boot.SpringApplication;
-import org.springframework.boot.autoconfigure.SpringBootApplication;
-
-/**
- * Spring Boot EntryPoint Class.
- */
-@SpringBootApplication
-public class App {
-
- /**
- * Program entry point.
- *
- * @param args command line args
- */
- public static void main(String[] args) {
- SpringApplication.run(App.class, args);
- }
-}
diff --git a/aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/Product.java b/aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/Product.java
deleted file mode 100644
index 3c214a58a9f5..000000000000
--- a/aggregator-microservices/aggregator-service/src/main/java/com/iluwatar/aggregator/microservices/Product.java
+++ /dev/null
@@ -1,58 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.aggregator.microservices;
-
-/**
- * Encapsulates all the data for a Product that clients will request.
- */
-public class Product {
-
- /**
- * The title of the product.
- */
- private String title;
-
-
- /**
- * The inventories of the product.
- */
- private int productInventories;
-
- public String getTitle() {
- return title;
- }
-
- public void setTitle(String title) {
- this.title = title;
- }
-
- public int getProductInventories() {
- return productInventories;
- }
-
- public void setProductInventories(int productInventories) {
- this.productInventories = productInventories;
- }
-
-}
diff --git a/aggregator-microservices/aggregator-service/src/main/resources/application.properties b/aggregator-microservices/aggregator-service/src/main/resources/application.properties
deleted file mode 100644
index f9e29f5a7234..000000000000
--- a/aggregator-microservices/aggregator-service/src/main/resources/application.properties
+++ /dev/null
@@ -1,23 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-server.port=50004
\ No newline at end of file
diff --git a/aggregator-microservices/etc/aggregator-microservice.png b/aggregator-microservices/etc/aggregator-microservice.png
deleted file mode 100644
index ad344a7e1e0f..000000000000
Binary files a/aggregator-microservices/etc/aggregator-microservice.png and /dev/null differ
diff --git a/aggregator-microservices/information-microservice/pom.xml b/aggregator-microservices/information-microservice/pom.xml
deleted file mode 100644
index f99d26b65665..000000000000
--- a/aggregator-microservices/information-microservice/pom.xml
+++ /dev/null
@@ -1,76 +0,0 @@
-
-
-
-
- aggregator-microservices
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
-
- information-microservice
- jar
-
-
-
- org.springframework
- spring-webmvc
-
-
- org.springframework.boot
- spring-boot-starter-web
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
-
-
-
-
- org.springframework.boot
- spring-boot-maven-plugin
-
-
-
- repackage
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.information.microservices.InformationApplication
-
-
-
-
-
-
-
-
-
diff --git a/aggregator-microservices/information-microservice/src/main/resources/application.properties b/aggregator-microservices/information-microservice/src/main/resources/application.properties
deleted file mode 100644
index b953a61da732..000000000000
--- a/aggregator-microservices/information-microservice/src/main/resources/application.properties
+++ /dev/null
@@ -1,23 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-server.port=51515
\ No newline at end of file
diff --git a/aggregator-microservices/inventory-microservice/pom.xml b/aggregator-microservices/inventory-microservice/pom.xml
deleted file mode 100644
index f7899aa8f307..000000000000
--- a/aggregator-microservices/inventory-microservice/pom.xml
+++ /dev/null
@@ -1,75 +0,0 @@
-
-
-
-
- aggregator-microservices
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
- inventory-microservice
-
- jar
-
-
- org.springframework
- spring-webmvc
-
-
- org.springframework.boot
- spring-boot-starter-web
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
-
-
-
-
- org.springframework.boot
- spring-boot-maven-plugin
-
-
-
- repackage
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.inventory.microservices.InventoryApplication
-
-
-
-
-
-
-
-
-
diff --git a/aggregator-microservices/inventory-microservice/src/main/resources/application.properties b/aggregator-microservices/inventory-microservice/src/main/resources/application.properties
deleted file mode 100644
index 9d2021f442d4..000000000000
--- a/aggregator-microservices/inventory-microservice/src/main/resources/application.properties
+++ /dev/null
@@ -1,23 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-server.port=51516
\ No newline at end of file
diff --git a/aggregator-microservices/pom.xml b/aggregator-microservices/pom.xml
deleted file mode 100644
index a63ec2f126a9..000000000000
--- a/aggregator-microservices/pom.xml
+++ /dev/null
@@ -1,42 +0,0 @@
-
-
-
-
- java-design-patterns
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
- aggregator-microservices
- pom
-
- information-microservice
- aggregator-service
- inventory-microservice
-
-
diff --git a/ambassador/README.md b/ambassador/README.md
index 78b3a885669f..fa08223feb75 100644
--- a/ambassador/README.md
+++ b/ambassador/README.md
@@ -1,37 +1,52 @@
---
-layout: pattern
-title: Ambassador
-folder: ambassador
-permalink: /patterns/ambassador/
-categories: Structural
-tags:
- - Decoupling
+title: "Ambassador Pattern in Java: Simplifying Remote Resource Management"
+shortTitle: Ambassador
+description: "Explore the Ambassador Pattern in Java, its benefits, use cases, and practical examples. Learn how to decouple and offload common functionalities to improve system performance and maintainability."
+category: Integration
+language: en
+tag:
+ - API design
+ - Decoupling
+ - Fault tolerance
+ - Proxy
+ - Resilience
+ - Scalability
---
-## Intent
-Provide a helper service instance on a client and offload common functionality away from a shared resource.
+## Intent of Ambassador Design Pattern
-## Explanation
-Real world example
+The Ambassador Pattern in Java helps offload common functionalities such as monitoring, logging, and routing from a shared resource to a helper service instance, enhancing performance and maintainability in distributed systems.
-> A remote service has many clients accessing a function it provides. The service is a legacy application and is impossible to update. Large numbers of requests from users are causing connectivity issues. New rules for request frequency should be implemented along with latency checks and client-side logging.
+## Detailed Explanation of Ambassador Pattern with Real-World Examples
+
+Real-world example
+
+> Imagine a busy hotel where guests frequently request restaurant reservations, event tickets, or transportation arrangements. Instead of each guest individually contacting these services, the hotel provides a concierge. The concierge handles these tasks on behalf of the guests, ensuring that reservations are made smoothly, tickets are booked on time, and transportation is scheduled efficiently.
+>
+> In this analogy, the guests are the client services, the external providers (restaurants, ticket vendors, transportation) are the remote services, and the concierge represents the ambassador service. This setup allows the guests to focus on enjoying their stay while the concierge manages the complexities of external interactions, providing a seamless and enhanced experience.
In plain words
-> Using the ambassador pattern, we can implement less-frequent polling from clients along with latency checks and logging.
+> With the Ambassador pattern, we can implement less-frequent polling from clients along with latency checks and logging.
Microsoft documentation states
-> An ambassador service can be thought of as an out-of-process proxy that is co-located with the client.
- This pattern can be useful for offloading common client connectivity tasks such as monitoring, logging, routing, security (such as TLS), and resiliency patterns in a language agnostic way. It is often used with legacy applications, or other applications that are difficult to modify, in order to extend their networking capabilities. It can also enable a specialized team to implement those features.
+> An ambassador service can be thought of as an out-of-process proxy which is co-located with the client. This pattern can be useful for offloading common client connectivity tasks such as monitoring, logging, routing, security (such as TLS), and resiliency patterns in a language agnostic way. It is often used with legacy applications, or other applications that are difficult to modify, in order to extend their networking capabilities. It can also enable a specialized team to implement those features.
+
+Sequence diagram
+
+
+
+## Programmatic Example of Ambassador Pattern in Java
-**Programmatic Example**
+In this example of the Ambassador Pattern in Java, we demonstrate how to implement latency checks, logging, and retry mechanisms to improve system reliability.
-With the above example in mind we will imitate the functionality in a simple manner. We have an interface implemented by the remote service as well as the ambassador service:
+A remote service has many clients accessing a function it provides. The service is a legacy application and is impossible to update. Large numbers of requests from users are causing connectivity issues. New rules for request frequency should be implemented along with latency checks and client-side logging.
+
+With the above introduction in mind we will imitate the functionality in this example. We have an interface implemented by the remote service as well as the ambassador service.
```java
interface RemoteServiceInterface {
-
long doRemoteFunction(int value) throws Exception;
}
```
@@ -39,9 +54,9 @@ interface RemoteServiceInterface {
A remote services represented as a singleton.
```java
-public class RemoteService implements RemoteServiceInterface {
- private static final Logger LOGGER = LoggerFactory.getLogger(RemoteService.class);
+@Slf4j
+public class RemoteService implements RemoteServiceInterface {
private static RemoteService service = null;
static synchronized RemoteService getRemoteService() {
@@ -51,7 +66,8 @@ public class RemoteService implements RemoteServiceInterface {
return service;
}
- private RemoteService() {}
+ private RemoteService() {
+ }
@Override
public long doRemoteFunction(int value) {
@@ -68,99 +84,108 @@ public class RemoteService implements RemoteServiceInterface {
}
```
-A service ambassador adding additional features such as logging, latency checks
+A service ambassador adds additional features such as logging and latency checks.
```java
-public class ServiceAmbassador implements RemoteServiceInterface {
-
- private static final Logger LOGGER = LoggerFactory.getLogger(ServiceAmbassador.class);
- private static final int RETRIES = 3;
- private static final int DELAY_MS = 3000;
- ServiceAmbassador() {
- }
-
- @Override
- public long doRemoteFunction(int value) {
- return safeCall(value);
- }
+@Slf4j
+public class ServiceAmbassador implements RemoteServiceInterface {
+ private static final int RETRIES = 3;
+ private static final int DELAY_MS = 3000;
- private long checkLatency(int value) {
- var startTime = System.currentTimeMillis();
- var result = RemoteService.getRemoteService().doRemoteFunction(value);
- var timeTaken = System.currentTimeMillis() - startTime;
+ ServiceAmbassador() {
+ }
- LOGGER.info("Time taken (ms): " + timeTaken);
- return result;
- }
+ @Override
+ public long doRemoteFunction(int value) {
+ return safeCall(value);
+ }
- private long safeCall(int value) {
- var retries = 0;
- var result = (long) FAILURE;
+ private long checkLatency(int value) {
+ var startTime = System.currentTimeMillis();
+ var result = RemoteService.getRemoteService().doRemoteFunction(value);
+ var timeTaken = System.currentTimeMillis() - startTime;
- for (int i = 0; i < RETRIES; i++) {
- if (retries >= RETRIES) {
- return FAILURE;
- }
+ LOGGER.info("Time taken (ms): " + timeTaken);
+ return result;
+ }
- if ((result = checkLatency(value)) == FAILURE) {
- LOGGER.info("Failed to reach remote: (" + (i + 1) + ")");
- retries++;
- try {
- sleep(DELAY_MS);
- } catch (InterruptedException e) {
- LOGGER.error("Thread sleep state interrupted", e);
+ private long safeCall(int value) {
+ var retries = 0;
+ var result = (long) FAILURE;
+
+ for (int i = 0; i < RETRIES; i++) {
+ if (retries >= RETRIES) {
+ return FAILURE;
+ }
+
+ if ((result = checkLatency(value)) == FAILURE) {
+ LOGGER.info("Failed to reach remote: (" + (i + 1) + ")");
+ retries++;
+ try {
+ sleep(DELAY_MS);
+ } catch (InterruptedException e) {
+ LOGGER.error("Thread sleep state interrupted", e);
+ }
+ } else {
+ break;
+ }
}
- } else {
- break;
- }
+ return result;
}
- return result;
- }
}
```
-A client has a local service ambassador used to interact with the remote service:
+A client has a local service ambassador used to interact with the remote service.
```java
-public class Client {
- private static final Logger LOGGER = LoggerFactory.getLogger(Client.class);
- private final ServiceAmbassador serviceAmbassador = new ServiceAmbassador();
+@Slf4j
+public class Client {
+ private final ServiceAmbassador serviceAmbassador = new ServiceAmbassador();
- long useService(int value) {
- var result = serviceAmbassador.doRemoteFunction(value);
- LOGGER.info("Service result: " + result);
- return result;
- }
+ long useService(int value) {
+ var result = serviceAmbassador.doRemoteFunction(value);
+ LOGGER.info("Service result: " + result);
+ return result;
+ }
}
```
-And here are two clients using the service.
+Here are two clients using the service.
```java
public class App {
- public static void main(String[] args) {
- var host1 = new Client();
- var host2 = new Client();
- host1.useService(12);
- host2.useService(73);
- }
+ public static void main(String[] args) {
+ var host1 = new Client();
+ var host2 = new Client();
+ host1.useService(12);
+ host2.useService(73);
+ }
}
```
-## Class diagram
-
+Here's the output for running the example:
-## Applicability
-Ambassador is applicable when working with a legacy remote service that cannot
-be modified or would be extremely difficult to modify. Connectivity features can
-be implemented on the client avoiding the need for changes on the remote service.
+```java
+Time taken(ms):111
+Service result:120
+Time taken(ms):931
+Failed to reach remote:(1)
+Time taken(ms):665
+Failed to reach remote:(2)
+Time taken(ms):538
+Failed to reach remote:(3)
+Service result:-1
+```
-* Ambassador provides a local interface for a remote service.
-* Ambassador provides logging, circuit breaking, retries and security on the client.
+## When to Use the Ambassador Pattern in Java
-## Typical Use Case
+* The Ambassador Pattern is particularly beneficial for Cloud Native and Microservices Architectures in Java. It helps in monitoring, logging, and securing inter-service communication, making it ideal for distributed systems.
+* Legacy System Integration: Facilitates communication with newer services by handling necessary but non-core functionalities.
+* Performance Enhancement: Can be used to cache results or compress data to improve communication efficiency.
+
+Typical use cases include:
* Control access to another object
* Implement logging
@@ -168,11 +193,44 @@ be implemented on the client avoiding the need for changes on the remote service
* Offload remote service tasks
* Facilitate network connection
-## Real world examples
+## Benefits and Trade-offs of Ambassador Pattern
+
+Benefits:
+
+* Separation of Concerns: Offloads cross-cutting concerns from the service logic, leading to cleaner, more maintainable code.
+* Reusable Infrastructure Logic: The ambassador pattern allows the same logic (e.g., logging, monitoring) to be reused across multiple services.
+* Improved Security: Centralizes security features like SSL termination or authentication, reducing the risk of misconfiguration.
+* Flexibility: Makes it easier to update or replace infrastructure concerns without modifying the service code.
+
+Trade-offs:
+* Increased Complexity: Adds another layer to the architecture, which can complicate the system design and debugging.
+* Potential Performance Overhead: The additional network hop can introduce latency and overhead, particularly if not optimized.
+* Deployment Overhead: Requires additional resources and management for deploying and scaling ambassador services.
+
+## Real-World Applications of Ambassador Pattern in Java
+
+* Service Mesh Implementations: In a service mesh architecture, like Istio or Linkerd, the Ambassador pattern is often employed as a sidecar proxy that handles inter-service communications. This includes tasks such as service discovery, routing, load balancing, telemetry (metrics and tracing), and security (authentication and authorization).
+* API Gateways: API gateways can use the Ambassador pattern to encapsulate common functionalities like rate limiting, caching, request shaping, and authentication. This allows backend services to focus on their core business logic without being burdened by these cross-cutting concerns.
+* Logging and Monitoring: An Ambassador can aggregate logs and metrics from various services and forward them to centralized monitoring tools like Prometheus or ELK Stack (Elasticsearch, Logstash, Kibana). This simplifies the logging and monitoring setup for each service and provides a unified view of the system's health.
+* Security: Security-related functionalities such as SSL/TLS termination, identity verification, and encryption can be managed by an Ambassador. This ensures consistent security practices across services and reduces the likelihood of security breaches due to misconfigurations.
+* Resilience: The Ambassador can implement resilience patterns like circuit breakers, retries, and timeouts. For instance, Netflix's Hystrix library can be used within an Ambassador to prevent cascading failures in a microservices ecosystem.
+* Database Proxy: Ambassadors can act as proxies for database connections, providing functionalities like connection pooling, read/write splitting for replicas, and query caching. This offloads significant complexity from the application services.
+* Legacy System Integration: In scenarios where modern microservices need to communicate with legacy systems, an Ambassador can serve as an intermediary that translates protocols, handles necessary transformations, and implements modern security practices, easing the integration process.
+* Network Optimization: For services deployed across different geographical locations or cloud regions, Ambassadors can optimize communication by compressing data, batching requests, or even implementing smart routing to reduce latency and costs.
* [Kubernetes-native API gateway for microservices](https://github.com/datawire/ambassador)
-## Credits
+## Related Java Design Patterns
+
+* [Circuit Breaker](https://java-design-patterns.com/patterns/circuit-breaker/): Often used in conjunction to manage fault tolerance by stopping calls to an unresponsive service.
+* [Decorator](https://java-design-patterns.com/patterns/decorator/): The decorator pattern is used to add functionality to an object dynamically, while the ambassador pattern is used to offload functionality to a separate object.
+* [Proxy](https://java-design-patterns.com/patterns/proxy/): Shares similarities with the proxy pattern, but the ambassador pattern specifically focuses on offloading ancillary functionalities.
+* Sidecar: A similar pattern used in the context of containerized applications, where a sidecar container provides additional functionality to the main application container.
+
+## References and Credits
-* [Ambassador pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/ambassador)
-* [Designing Distributed Systems: Patterns and Paradigms for Scalable, Reliable Services](https://books.google.co.uk/books?id=6BJNDwAAQBAJ&pg=PT35&lpg=PT35&dq=ambassador+pattern+in+real+world&source=bl&ots=d2e7GhYdHi&sig=Lfl_MDnCgn6lUcjzOg4GXrN13bQ&hl=en&sa=X&ved=0ahUKEwjk9L_18rrbAhVpKcAKHX_KA7EQ6AEIWTAI#v=onepage&q=ambassador%20pattern%20in%20real%20world&f=false)
+* [Building Microservices: Designing Fine-Grained Systems](https://amzn.to/43aGpSR)
+* [Cloud Native Patterns: Designing Change-tolerant Software](https://amzn.to/3wUAl4O)
+* [Designing Distributed Systems: Patterns and Paradigms for Scalable, Reliable Services](https://amzn.to/3T9g9Uj)
+* [Microservices Patterns: With examples in Java](https://amzn.to/3UyWD5O)
+* [Ambassador pattern (Microsoft)](https://docs.microsoft.com/en-us/azure/architecture/patterns/ambassador)
diff --git a/ambassador/etc/ambassador-sequence-diagram.png b/ambassador/etc/ambassador-sequence-diagram.png
new file mode 100644
index 000000000000..71e6a947c5dd
Binary files /dev/null and b/ambassador/etc/ambassador-sequence-diagram.png differ
diff --git a/ambassador/pom.xml b/ambassador/pom.xml
index 6d6a9894de20..15e4a07f0dc3 100644
--- a/ambassador/pom.xml
+++ b/ambassador/pom.xml
@@ -1,53 +1,70 @@
-
-
-
- java-design-patterns
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
- ambassador
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.ambassador.App
-
-
-
-
-
-
-
-
+
+
+
+ java-design-patterns
+ com.iluwatar
+ 1.26.0-SNAPSHOT
+
+ 4.0.0
+ ambassador
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.ambassador.App
+
+
+
+
+
+
+
+
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/App.java b/ambassador/src/main/java/com/iluwatar/ambassador/App.java
index 087fc39c08f9..8de149fe0813 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/App.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/App.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,14 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
/**
* The ambassador pattern creates a helper service that sends network requests on behalf of a
* client. It is often used in cloud-based applications to offload features of a remote service.
*
- * An ambassador service can be thought of as an out-of-process proxy that is co-located with
- * the client. Similar to the proxy design pattern, the ambassador service provides an interface for
+ *
An ambassador service can be thought of as an out-of-process proxy that is co-located with the
+ * client. Similar to the proxy design pattern, the ambassador service provides an interface for
* another remote service. In addition to the interface, the ambassador provides extra functionality
* and features, specifically offloaded common connectivity tasks. This usually consists of
* monitoring, logging, routing, security etc. This is extremely useful in legacy applications where
@@ -36,14 +37,11 @@
* capabilities.
*
*
In this example, we will the ({@link ServiceAmbassador}) class represents the ambassador while
- * the
- * ({@link RemoteService}) class represents a remote application.
+ * the ({@link RemoteService}) class represents a remote application.
*/
public class App {
- /**
- * Entry point.
- */
+ /** Entry point. */
public static void main(String[] args) {
var host1 = new Client();
var host2 = new Client();
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/Client.java b/ambassador/src/main/java/com/iluwatar/ambassador/Client.java
index 70d52e799742..0baabf4ffc06 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/Client.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/Client.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,23 +22,19 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
-/**
- * A simple Client.
- */
+/** A simple Client. */
+@Slf4j
public class Client {
- private static final Logger LOGGER = LoggerFactory.getLogger(Client.class);
private final ServiceAmbassador serviceAmbassador = new ServiceAmbassador();
long useService(int value) {
var result = serviceAmbassador.doRemoteFunction(value);
- LOGGER.info("Service result: " + result);
+ LOGGER.info("Service result: {}", result);
return result;
}
}
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java
index a80806851e6b..d99348040cfe 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,21 +22,17 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
import static java.lang.Thread.sleep;
import com.iluwatar.ambassador.util.RandomProvider;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
-/**
- * A remote legacy application represented by a Singleton implementation.
- */
+/** A remote legacy application represented by a Singleton implementation. */
+@Slf4j
public class RemoteService implements RemoteServiceInterface {
private static final int THRESHOLD = 200;
- private static final Logger LOGGER = LoggerFactory.getLogger(RemoteService.class);
private static RemoteService service = null;
private final RandomProvider randomProvider;
@@ -49,9 +47,7 @@ private RemoteService() {
this(Math::random);
}
- /**
- * This constructor is used for testing purposes only.
- */
+ /** This constructor is used for testing purposes only. */
RemoteService(RandomProvider randomProvider) {
this.randomProvider = randomProvider;
}
@@ -62,7 +58,7 @@ private RemoteService() {
*
* @param value integer value to be multiplied.
* @return if waitTime is less than {@link RemoteService#THRESHOLD}, it returns value * 10,
- * otherwise {@link RemoteServiceInterface#FAILURE}.
+ * otherwise {@link RemoteServiceStatus#FAILURE}.
*/
@Override
public long doRemoteFunction(int value) {
@@ -73,7 +69,10 @@ public long doRemoteFunction(int value) {
sleep(waitTime);
} catch (InterruptedException e) {
LOGGER.error("Thread sleep state interrupted", e);
+ Thread.currentThread().interrupt();
}
- return waitTime <= THRESHOLD ? value * 10 : FAILURE;
+ return waitTime <= THRESHOLD
+ ? value * 10
+ : RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue();
}
}
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java
index 013015936957..aa6012bae33f 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,14 +22,10 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
-/**
- * Interface shared by ({@link RemoteService}) and ({@link ServiceAmbassador}).
- */
+/** Interface shared by ({@link RemoteService}) and ({@link ServiceAmbassador}). */
interface RemoteServiceInterface {
- int FAILURE = -1;
- long doRemoteFunction(int value) throws Exception;
+ long doRemoteFunction(int value);
}
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceStatus.java b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceStatus.java
new file mode 100644
index 000000000000..8549ed7247f3
--- /dev/null
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceStatus.java
@@ -0,0 +1,44 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.ambassador;
+
+import lombok.Getter;
+
+/**
+ * Holds information regarding the status of the Remote Service.
+ *
+ *
This Enum replaces the integer value previously stored in {@link RemoteServiceInterface} as
+ * SonarCloud was identifying it as an issue. All test cases have been checked after changes,
+ * without failures.
+ */
+public enum RemoteServiceStatus {
+ FAILURE(-1);
+
+ @Getter private final long remoteServiceStatusValue;
+
+ RemoteServiceStatus(long remoteServiceStatusValue) {
+ this.remoteServiceStatusValue = remoteServiceStatusValue;
+ }
+}
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java b/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java
index a9d34581c614..4d310169770b 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,27 +22,25 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
+import static com.iluwatar.ambassador.RemoteServiceStatus.FAILURE;
import static java.lang.Thread.sleep;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
/**
* ServiceAmbassador provides an interface for a ({@link Client}) to access ({@link RemoteService}).
* The interface adds logging, latency testing and usage of the service in a safe way that will not
* add stress to the remote service when connectivity issues occur.
*/
+@Slf4j
public class ServiceAmbassador implements RemoteServiceInterface {
- private static final Logger LOGGER = LoggerFactory.getLogger(ServiceAmbassador.class);
private static final int RETRIES = 3;
private static final int DELAY_MS = 3000;
- ServiceAmbassador() {
- }
+ ServiceAmbassador() {}
@Override
public long doRemoteFunction(int value) {
@@ -52,26 +52,27 @@ private long checkLatency(int value) {
var result = RemoteService.getRemoteService().doRemoteFunction(value);
var timeTaken = System.currentTimeMillis() - startTime;
- LOGGER.info("Time taken (ms): " + timeTaken);
+ LOGGER.info("Time taken (ms): {}", timeTaken);
return result;
}
private long safeCall(int value) {
var retries = 0;
- var result = (long) FAILURE;
+ var result = FAILURE.getRemoteServiceStatusValue();
for (int i = 0; i < RETRIES; i++) {
if (retries >= RETRIES) {
- return FAILURE;
+ return FAILURE.getRemoteServiceStatusValue();
}
- if ((result = checkLatency(value)) == FAILURE) {
- LOGGER.info("Failed to reach remote: (" + (i + 1) + ")");
+ if ((result = checkLatency(value)) == FAILURE.getRemoteServiceStatusValue()) {
+ LOGGER.info("Failed to reach remote: ({})", i + 1);
retries++;
try {
sleep(DELAY_MS);
} catch (InterruptedException e) {
LOGGER.error("Thread sleep state interrupted", e);
+ Thread.currentThread().interrupt();
}
} else {
break;
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/util/RandomProvider.java b/ambassador/src/main/java/com/iluwatar/ambassador/util/RandomProvider.java
index 5948472c0062..4eba2fada7fa 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/util/RandomProvider.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/util/RandomProvider.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +22,9 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador.util;
-/**
- * An interface for randomness. Useful for testing purposes.
- */
+/** An interface for randomness. Useful for testing purposes. */
public interface RandomProvider {
double random();
}
diff --git a/ambassador/src/test/java/com/iluwatar/ambassador/AppTest.java b/ambassador/src/test/java/com/iluwatar/ambassador/AppTest.java
index c9a4d09b6965..ddb2d6eff411 100644
--- a/ambassador/src/test/java/com/iluwatar/ambassador/AppTest.java
+++ b/ambassador/src/test/java/com/iluwatar/ambassador/AppTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,18 +22,24 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
import org.junit.jupiter.api.Test;
-/**
- * Application test
- */
+/** Application test */
class AppTest {
+ /**
+ * Issue: Add at least one assertion to this test case.
+ *
+ *
Solution: Inserted assertion to check whether the execution of the main method in {@link
+ * App} throws an exception.
+ */
@Test
- void test() {
- App.main(new String[]{});
+ void shouldExecuteApplicationWithoutException() {
+
+ assertDoesNotThrow(() -> App.main(new String[] {}));
}
}
diff --git a/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java b/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java
index 12a93a1cbc53..24603efff9d4 100644
--- a/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java
+++ b/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +22,13 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
-import org.junit.jupiter.api.Test;
-
import static org.junit.jupiter.api.Assertions.assertTrue;
-/**
- * Test for {@link Client}
- */
+import org.junit.jupiter.api.Test;
+
+/** Test for {@link Client} */
class ClientTest {
@Test
@@ -37,6 +36,7 @@ void test() {
Client client = new Client();
var result = client.useService(10);
- assertTrue(result == 100 || result == RemoteService.FAILURE);
+ assertTrue(
+ result == 100 || result == RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue());
}
}
diff --git a/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java b/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java
index 3cfea262375a..81e4f744128f 100644
--- a/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java
+++ b/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -28,16 +29,14 @@
import com.iluwatar.ambassador.util.RandomProvider;
import org.junit.jupiter.api.Test;
-/**
- * Test for {@link RemoteService}
- */
+/** Test for {@link RemoteService} */
class RemoteServiceTest {
@Test
void testFailedCall() {
var remoteService = new RemoteService(new StaticRandomProvider(0.21));
var result = remoteService.doRemoteFunction(10);
- assertEquals(RemoteServiceInterface.FAILURE, result);
+ assertEquals(RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue(), result);
}
@Test
@@ -48,7 +47,7 @@ void testSuccessfulCall() {
}
private static class StaticRandomProvider implements RandomProvider {
- private double value;
+ private final double value;
StaticRandomProvider(double value) {
this.value = value;
diff --git a/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java b/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java
index 8eb55b30a12f..0543b2e7e370 100644
--- a/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java
+++ b/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,21 +22,19 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.ambassador;
-import org.junit.jupiter.api.Test;
-
import static org.junit.jupiter.api.Assertions.assertTrue;
-/**
- * Test for {@link ServiceAmbassador}
- */
+import org.junit.jupiter.api.Test;
+
+/** Test for {@link ServiceAmbassador} */
class ServiceAmbassadorTest {
@Test
void test() {
long result = new ServiceAmbassador().doRemoteFunction(10);
- assertTrue(result == 100 || result == RemoteServiceInterface.FAILURE);
+ assertTrue(
+ result == 100 || result == RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue());
}
}
diff --git a/anti-corruption-layer/README.md b/anti-corruption-layer/README.md
new file mode 100644
index 000000000000..9b6042850eba
--- /dev/null
+++ b/anti-corruption-layer/README.md
@@ -0,0 +1,185 @@
+---
+title: "Anti-Corruption Layer Pattern in Java: Ensuring System Integrity Amidst Legacy Systems"
+shortTitle: Anti-Corruption Layer
+description: "Learn how the Anti-Corruption Layer design pattern helps in decoupling subsystems, preventing data corruption, and facilitating seamless integration in Java applications."
+category: Integration
+language: en
+tag:
+ - Architecture
+ - Decoupling
+ - Integration
+ - Isolation
+ - Layered architecture
+ - Migration
+ - Modernization
+ - Refactoring
+ - Wrapping
+---
+
+## Also known as
+
+* ACL
+* Interface layer
+* Translation layer
+
+## Intent of Anti-Corruption Layer Design Pattern
+
+The Anti-Corruption Layer (ACL) is a crucial design pattern in Java development, particularly for system integration and maintaining data integrity. Implement a façade or adapter layer between different subsystems that don't share the same semantics. It translates between different data formats and systems, ensuring that the integration between systems does not lead to corruption of business logic or data integrity.
+
+## Detailed Explanation of Anti-Corruption Layer Pattern with Real-World Examples
+
+Real-world example
+
+> This example demonstrates how the Anti-Corruption Layer ensures seamless integration between legacy systems and modern platforms, crucial for maintaining business logic integrity during system migration.
+>
+> Imagine a large retail company transitioning its inventory management system from an old legacy software to a new modern platform. The legacy system has been in use for decades and contains complex business rules and data formats that are incompatible with the new system. Instead of directly connecting the new system to the legacy one, the company implements an Anti-Corruption Layer (ACL).
+>
+> The ACL acts as a mediator, translating and adapting data between the two systems. When the new system requests inventory data, the ACL translates the request into a format the legacy system understands, retrieves the data, and then translates it back into a format suitable for the new system. This approach ensures that the new system remains unaffected by the intricacies of the legacy system, preventing corruption of data and business logic while facilitating a smooth transition.
+
+In plain words
+
+> The Anti-Corruption Layer design pattern protects a system from the complexities and changes of external systems by providing an intermediary translation layer.
+
+[Microsoft's documentation](https://learn.microsoft.com/en-us/azure/architecture/patterns/anti-corruption-layer) says
+
+> Implement a façade or adapter layer between different subsystems that don't share the same semantics. This layer translates requests that one subsystem makes to the other subsystem. Use this pattern to ensure that an application's design is not limited by dependencies on outside subsystems. This pattern was first described by Eric Evans in Domain-Driven Design.
+
+Sequence diagram
+
+
+
+## Programmatic Example of Anti-Corruption Layer Pattern in Java
+
+The ACL design pattern in Java provides an intermediary layer that translates data formats, ensuring that integration between different systems does not lead to data corruption.
+
+Here are 2 shop-ordering systems: `Legacy` and `Modern`.
+
+The aforementioned systems have different domain models and have to operate simultaneously. Since they work independently the orders can come either from the `Legacy` or `Modern` system. Therefore, the system that receives the legacyOrder needs to check if the legacyOrder is valid and not present in the other system. Then it can place the legacyOrder in its own system.
+
+But for that, the system needs to know the domain model of the other system and to avoid that, the anti-corruption layer(ACL) is introduced. The ACL is a layer that translates the domain model of the `Legacy` system to the domain model of the `Modern` system and vice versa. Also, it hides all other operations with the other system, uncoupling the systems.
+
+Domain model of the `Legacy` system:
+
+```java
+public class LegacyOrder {
+ private String id;
+ private String customer;
+ private String item;
+ private String qty;
+ private String price;
+}
+```
+
+Domain model of the `Modern` system:
+
+```java
+public class ModernOrder {
+ private String id;
+ private Customer customer;
+
+ private Shipment shipment;
+
+ private String extra;
+}
+
+public class Customer {
+ private String address;
+}
+
+public class Shipment {
+ private String item;
+ private String qty;
+ private String price;
+}
+```
+
+Anti-corruption layer:
+
+```java
+public class AntiCorruptionLayer {
+
+ @Autowired
+ private ModernShop modernShop;
+
+ @Autowired
+ private LegacyShop legacyShop;
+
+ public Optional findOrderInModernSystem(String id) {
+ return modernShop.findOrder(id).map(o -> /* map to legacyOrder*/);
+ }
+
+ public Optional findOrderInLegacySystem(String id) {
+ return legacyShop.findOrder(id).map(o -> /* map to modernOrder*/);
+ }
+
+}
+```
+
+The connection between the systems. Wherever the `Legacy` or `Modern` system needs to communicate with the counterpart the ACL needs to be used to avoid corrupting the current domain model. The example below shows how the `Legacy` system places an order with a validation from the `Modern` system.
+
+```java
+public class LegacyShop {
+ @Autowired
+ private AntiCorruptionLayer acl;
+
+ public void placeOrder(LegacyOrder legacyOrder) throws ShopException {
+
+ String id = legacyOrder.getId();
+
+ Optional orderInModernSystem = acl.findOrderInModernSystem(id);
+
+ if (orderInModernSystem.isPresent()) {
+ // order is already in the modern system
+ } else {
+ // place order in the current system
+ }
+ }
+}
+```
+
+## When to Use the Anti-Corruption Layer Pattern in Java
+
+Use this pattern when:
+
+* A migration is planned to happen over multiple stages, but integration between new and legacy systems needs to be maintained
+* Two or more subsystems have different semantics, but still need to communicate
+* When integrating with legacy systems or external systems where direct integration might pollute the domain model of the new system
+* In scenarios where different subsystems within a larger system use different data formats or structures
+* When there is a need to ensure loose coupling between different subsystems or external services to facilitate easier maintenance and scalability
+
+## Anti-Corruption Layer Pattern Java Tutorials
+
+* [Anti-Corruption Layer (Microsoft)](https://learn.microsoft.com/en-us/azure/architecture/patterns/anti-corruption-layer)
+* [Anti-Corruption Layer Pattern (Amazon)](https://docs.aws.amazon.com/prescriptive-guidance/latest/cloud-design-patterns/acl.html)
+
+## Real-World Applications of Anti-Corruption Layer Pattern in Java
+
+* Microservices architectures where individual services must communicate without being tightly coupled to each other’s data schemas
+* Enterprise systems integration, especially when integrating modern systems with legacy systems
+* In bounded contexts within Domain-Driven Design (DDD) to maintain the integrity of a domain model when interacting with external systems or subsystems
+
+## Benefits and Trade-offs of Anti-Corruption Layer Pattern
+
+Benefits:
+
+* Protects the integrity of the domain model by providing a clear boundary
+* Promotes loose coupling between systems, making the system more resilient to changes in external systems
+* Facilitates cleaner and more maintainable code by isolating integration code from business logic
+
+Trade-offs:
+
+* Introduces additional complexity and potential performance overhead due to the translation process
+* Requires extra effort in design and implementation to ensure the layer is effective without becoming a bottleneck
+* Can lead to duplication of models if not carefully managed
+
+## Related Java Design Patterns
+
+* [Adapter](https://java-design-patterns.com/patterns/adapter/): The Anti-Corruption Layer can be implemented using the Adapter pattern to translate between different data formats or structures
+* [Facade](https://java-design-patterns.com/patterns/facade/): The Anti-Corruption Layer can be seen as a specialized form of the Facade pattern that is used to isolate different subsystems
+* [Gateway](https://java-design-patterns.com/patterns/gateway/): The Anti-Corruption Layer can be used as a Gateway to external systems to provide a unified interface
+
+## References and Credits
+
+* [Domain-Driven Design: Tackling Complexity in the Heart of Software](https://amzn.to/3vptcJz)
+* [Implementing Domain-Driven Design](https://amzn.to/3ISOSRA)
+* [Patterns of Enterprise Application Architecture](https://amzn.to/3WfKBPR)
diff --git a/anti-corruption-layer/etc/anti-corruption-layer-sequence-diagram.png b/anti-corruption-layer/etc/anti-corruption-layer-sequence-diagram.png
new file mode 100644
index 000000000000..835ff4e84a0f
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diff --git a/anti-corruption-layer/etc/anti-corruption-layer.urm.png b/anti-corruption-layer/etc/anti-corruption-layer.urm.png
new file mode 100644
index 000000000000..96e432121e7e
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diff --git a/anti-corruption-layer/etc/anti-corruption-layer.urm.puml b/anti-corruption-layer/etc/anti-corruption-layer.urm.puml
new file mode 100644
index 000000000000..6b1d1cdb9b81
--- /dev/null
+++ b/anti-corruption-layer/etc/anti-corruption-layer.urm.puml
@@ -0,0 +1,25 @@
+@startuml
+package com.iluwatar.corruption {
+class LegacyShop {
+ private Store store;
+ private AntiCorruptionLayer acl;
+}
+
+class ModernShop {
+ private Store store;
+ private AntiCorruptionLayer acl;
+}
+
+class AntiCorruptionLayer{
+ private LegacyShop legacyShop;
+ private ModernShop modernShop;
+
+
+ }
+LegacyShop ---> "findOrderInModernSystem" AntiCorruptionLayer
+ModernShop ---> "findOrderInLegacySystem" AntiCorruptionLayer
+AntiCorruptionLayer ..|> ModernShop
+AntiCorruptionLayer ..|> LegacyShop
+}
+
+@enduml
\ No newline at end of file
diff --git a/anti-corruption-layer/pom.xml b/anti-corruption-layer/pom.xml
new file mode 100644
index 000000000000..2fddfd3ecc46
--- /dev/null
+++ b/anti-corruption-layer/pom.xml
@@ -0,0 +1,72 @@
+
+
+
+
+ java-design-patterns
+ com.iluwatar
+ 1.26.0-SNAPSHOT
+
+ 4.0.0
+ anti-corruption-layer
+ jar
+
+
+ org.springframework.boot
+ spring-boot-starter
+
+
+ org.springframework.boot
+ spring-boot-starter-test
+ test
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.corruption.App
+
+
+
+
+
+
+
+
+
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/App.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/App.java
new file mode 100644
index 000000000000..f7cf8f075f83
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/App.java
@@ -0,0 +1,40 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * This layer translates communications between the two systems, allowing one system to remain
+ * unchanged while the other can avoid compromising its design and technological approach.
+ */
+@SpringBootApplication
+public class App {
+
+ public static void main(String[] args) {
+ SpringApplication.run(App.class, args);
+ }
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/package-info.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/package-info.java
new file mode 100644
index 000000000000..880d98c7d5b0
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/package-info.java
@@ -0,0 +1,48 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+/**
+ * Context and problem Most applications rely on other systems for some data or functionality. For
+ * example, when a legacy application is migrated to a modern system, it may still need existing
+ * legacy resources. New features must be able to call the legacy system. This is especially true of
+ * gradual migrations, where different features of a larger application are moved to a modern system
+ * over time.
+ *
+ * Often these legacy systems suffer from quality issues such as convoluted data schemas or
+ * obsolete APIs. The features and technologies used in legacy systems can vary widely from more
+ * modern systems. To interoperate with the legacy system, the new application may need to support
+ * outdated infrastructure, protocols, data models, APIs, or other features that you wouldn't
+ * otherwise put into a modern application.
+ *
+ *
Maintaining access between new and legacy systems can force the new system to adhere to at
+ * least some of the legacy system's APIs or other semantics. When these legacy features have
+ * quality issues, supporting them "corrupts" what might otherwise be a cleanly designed modern
+ * application. Similar issues can arise with any external system that your development team doesn't
+ * control, not just legacy systems.
+ *
+ *
Solution Isolate the different subsystems by placing an anti-corruption layer between them.
+ * This layer translates communications between the two systems, allowing one system to remain
+ * unchanged while the other can avoid compromising its design and technological approach.
+ */
+package com.iluwatar.corruption;
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/AntiCorruptionLayer.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/AntiCorruptionLayer.java
new file mode 100644
index 000000000000..4e8a17fa5d2a
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/AntiCorruptionLayer.java
@@ -0,0 +1,66 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system;
+
+import com.iluwatar.corruption.system.legacy.LegacyShop;
+import com.iluwatar.corruption.system.modern.Customer;
+import com.iluwatar.corruption.system.modern.ModernOrder;
+import com.iluwatar.corruption.system.modern.Shipment;
+import java.util.Optional;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+/**
+ * The class represents an anti-corruption layer. The main purpose of the class is to provide a
+ * layer between the modern and legacy systems. The class is responsible for converting the data
+ * from one system to another decoupling the systems to each other
+ *
+ *
It allows using one system a domain model of the other system without changing the domain
+ * model of the system.
+ */
+@Service
+public class AntiCorruptionLayer {
+
+ @Autowired private LegacyShop legacyShop;
+
+ /**
+ * The method converts the order from the legacy system to the modern system.
+ *
+ * @param id the id of the order
+ * @return the order in the modern system
+ */
+ public Optional findOrderInLegacySystem(String id) {
+
+ return legacyShop
+ .findOrder(id)
+ .map(
+ o ->
+ new ModernOrder(
+ o.getId(),
+ new Customer(o.getCustomer()),
+ new Shipment(o.getItem(), o.getQty(), o.getPrice()),
+ ""));
+ }
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/DataStore.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/DataStore.java
new file mode 100644
index 000000000000..e84578528be7
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/DataStore.java
@@ -0,0 +1,49 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system;
+
+import java.util.HashMap;
+import java.util.Optional;
+
+/**
+ * The class represents a data store for the modern system.
+ *
+ * @param the type of the value stored in the data store
+ */
+public abstract class DataStore {
+ private final HashMap inner;
+
+ public DataStore() {
+ inner = new HashMap<>();
+ }
+
+ public Optional get(String key) {
+ return Optional.ofNullable(inner.get(key));
+ }
+
+ public Optional put(String key, V value) {
+ return Optional.ofNullable(inner.put(key, value));
+ }
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/ShopException.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/ShopException.java
new file mode 100644
index 000000000000..c0acd288ed0c
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/ShopException.java
@@ -0,0 +1,50 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system;
+
+/** The class represents a general exception for the shop. */
+public class ShopException extends Exception {
+ public ShopException(String message) {
+ super(message);
+ }
+
+ /**
+ * Throws an exception that the order is already placed but has an incorrect data.
+ *
+ * @param lhs the incoming order
+ * @param rhs the existing order
+ * @return the exception
+ * @throws ShopException the exception
+ */
+ public static ShopException throwIncorrectData(String lhs, String rhs) throws ShopException {
+ throw new ShopException(
+ "The order is already placed but has an incorrect data:\n"
+ + "Incoming order: "
+ + lhs
+ + "\n"
+ + "Existing order: "
+ + rhs);
+ }
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyOrder.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyOrder.java
new file mode 100644
index 000000000000..45faa06cb26c
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyOrder.java
@@ -0,0 +1,43 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.legacy;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+/**
+ * The class represents an order in the legacy system. The class is used by the legacy system to
+ * store the data.
+ */
+@Data
+@AllArgsConstructor
+public class LegacyOrder {
+ private String id;
+ private String customer;
+
+ private String item;
+ private int qty;
+ private int price;
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyShop.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyShop.java
new file mode 100644
index 000000000000..b74eb1c29718
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyShop.java
@@ -0,0 +1,52 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.legacy;
+
+import java.util.Optional;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+/**
+ * The class represents a legacy shop system. The main purpose is to place the order from the
+ * customers.
+ */
+@Service
+public class LegacyShop {
+ @Autowired private LegacyStore store;
+
+ /**
+ * Places the order in the legacy system. If the order is already present in the modern system,
+ * then the order is placed only if the data is the same. If the order is not present in the
+ * modern system, then the order is placed in the legacy system.
+ */
+ public void placeOrder(LegacyOrder legacyOrder) {
+ store.put(legacyOrder.getId(), legacyOrder);
+ }
+
+ /** Finds the order in the legacy system. */
+ public Optional findOrder(String orderId) {
+ return store.get(orderId);
+ }
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyStore.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyStore.java
new file mode 100644
index 000000000000..ec1d613a7235
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/legacy/LegacyStore.java
@@ -0,0 +1,35 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.legacy;
+
+import com.iluwatar.corruption.system.DataStore;
+import org.springframework.stereotype.Service;
+
+/**
+ * The class represents a data store for the legacy system. The class is used by the legacy system
+ * to store the data.
+ */
+@Service
+public class LegacyStore extends DataStore {}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/Customer.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/Customer.java
new file mode 100644
index 000000000000..130f36d39674
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/Customer.java
@@ -0,0 +1,35 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.modern;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+/** The class represents a customer in the modern system. */
+@Data
+@AllArgsConstructor
+public class Customer {
+ private String address;
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernOrder.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernOrder.java
new file mode 100644
index 000000000000..7b62985015d6
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernOrder.java
@@ -0,0 +1,40 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.modern;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+/** The class represents an order in the modern system. */
+@Data
+@AllArgsConstructor
+public class ModernOrder {
+ private String id;
+ private Customer customer;
+
+ private Shipment shipment;
+
+ private String extra;
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernShop.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernShop.java
new file mode 100644
index 000000000000..24080abe1533
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernShop.java
@@ -0,0 +1,67 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.modern;
+
+import com.iluwatar.corruption.system.AntiCorruptionLayer;
+import com.iluwatar.corruption.system.ShopException;
+import java.util.Optional;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+/**
+ * The class represents a modern shop system. The main purpose of the class is to place orders and
+ * find orders.
+ */
+@Service
+public class ModernShop {
+ @Autowired private ModernStore store;
+
+ @Autowired private AntiCorruptionLayer acl;
+
+ /**
+ * Places the order in the modern system. If the order is already present in the legacy system,
+ * then no need to place it again.
+ */
+ public void placeOrder(ModernOrder order) throws ShopException {
+
+ String id = order.getId();
+ // check if the order is already present in the legacy system
+ Optional orderInObsoleteSystem = acl.findOrderInLegacySystem(id);
+
+ if (orderInObsoleteSystem.isPresent()) {
+ var legacyOrder = orderInObsoleteSystem.get();
+ if (!order.equals(legacyOrder)) {
+ throw ShopException.throwIncorrectData(legacyOrder.toString(), order.toString());
+ }
+ } else {
+ store.put(id, order);
+ }
+ }
+
+ /** Finds the order in the modern system. */
+ public Optional findOrder(String orderId) {
+ return store.get(orderId);
+ }
+}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernStore.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernStore.java
new file mode 100644
index 000000000000..4fb3952fae5e
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/ModernStore.java
@@ -0,0 +1,32 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.modern;
+
+import com.iluwatar.corruption.system.DataStore;
+import org.springframework.stereotype.Service;
+
+/** The class represents a data store for the modern system. */
+@Service
+public class ModernStore extends DataStore {}
diff --git a/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/Shipment.java b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/Shipment.java
new file mode 100644
index 000000000000..085a3921ceeb
--- /dev/null
+++ b/anti-corruption-layer/src/main/java/com/iluwatar/corruption/system/modern/Shipment.java
@@ -0,0 +1,40 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system.modern;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+/**
+ * The class represents a shipment in the modern system. The class is used by the modern system to
+ * store the data.
+ */
+@Data
+@AllArgsConstructor
+public class Shipment {
+ private String item;
+ private int qty;
+ private int price;
+}
diff --git a/anti-corruption-layer/src/main/resources/application.properties b/anti-corruption-layer/src/main/resources/application.properties
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/anti-corruption-layer/src/test/java/com/iluwatar/corruption/system/AntiCorruptionLayerTest.java b/anti-corruption-layer/src/test/java/com/iluwatar/corruption/system/AntiCorruptionLayerTest.java
new file mode 100644
index 000000000000..ee46d124eee6
--- /dev/null
+++ b/anti-corruption-layer/src/test/java/com/iluwatar/corruption/system/AntiCorruptionLayerTest.java
@@ -0,0 +1,96 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.corruption.system;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import com.iluwatar.corruption.system.legacy.LegacyOrder;
+import com.iluwatar.corruption.system.legacy.LegacyShop;
+import com.iluwatar.corruption.system.modern.Customer;
+import com.iluwatar.corruption.system.modern.ModernOrder;
+import com.iluwatar.corruption.system.modern.ModernShop;
+import com.iluwatar.corruption.system.modern.Shipment;
+import java.util.Optional;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+@ExtendWith(SpringExtension.class)
+@SpringBootTest
+public class AntiCorruptionLayerTest {
+
+ @Autowired private LegacyShop legacyShop;
+
+ @Autowired private ModernShop modernShop;
+
+ /**
+ * Test the anti-corruption layer. Main intention is to demonstrate how the anti-corruption layer
+ * works. The 2 shops (modern and legacy) should operate independently and in the same time
+ * synchronize the data.
+ */
+ @Test
+ public void antiCorruptionLayerTest() throws ShopException {
+ // a new order comes to the legacy shop.
+ LegacyOrder legacyOrder = new LegacyOrder("1", "addr1", "item1", 1, 1);
+ // place the order in the legacy shop.
+ legacyShop.placeOrder(legacyOrder);
+ // the order is placed as usual since there is no other orders with the id in the both systems.
+ Optional legacyOrderWithIdOne = legacyShop.findOrder("1");
+ assertEquals(Optional.of(legacyOrder), legacyOrderWithIdOne);
+
+ // a new order (or maybe just the same order) appears in the modern shop
+ ModernOrder modernOrder =
+ new ModernOrder("1", new Customer("addr1"), new Shipment("item1", 1, 1), "");
+ // the system places it, but it checks if there is an order with the same id in the legacy shop.
+ modernShop.placeOrder(modernOrder);
+
+ Optional modernOrderWithIdOne = modernShop.findOrder("1");
+ // there is no new order placed since there is already an order with the same id in the legacy
+ // shop.
+ assertTrue(modernOrderWithIdOne.isEmpty());
+ }
+
+ /**
+ * Test the anti-corruption layer when a conflict occurs between systems. This test ensures that
+ * an exception is thrown when conflicting orders are placed.
+ */
+ @Test
+ public void antiCorruptionLayerWithExTest() throws ShopException {
+ // a new order comes to the legacy shop.
+ LegacyOrder legacyOrder = new LegacyOrder("1", "addr1", "item1", 1, 1);
+ // place the order in the legacy shop.
+ legacyShop.placeOrder(legacyOrder);
+ // the order is placed as usual since there is no other orders with the id in the both systems.
+ Optional legacyOrderWithIdOne = legacyShop.findOrder("1");
+ assertEquals(Optional.of(legacyOrder), legacyOrderWithIdOne);
+ // a new order but with the same id and different data appears in the modern shop
+ ModernOrder modernOrder =
+ new ModernOrder("1", new Customer("addr1"), new Shipment("item1", 10, 1), "");
+ // the system rejects the order since there are 2 orders with contradiction there.
+ assertThrows(ShopException.class, () -> modernShop.placeOrder(modernOrder));
+ }
+}
diff --git a/api-gateway/README.md b/api-gateway/README.md
deleted file mode 100644
index 3a4f13e35e62..000000000000
--- a/api-gateway/README.md
+++ /dev/null
@@ -1,30 +0,0 @@
----
-layout: pattern
-title: API Gateway
-folder: api-gateway
-permalink: /patterns/api-gateway/
-categories: Architectural
-tags:
-- Cloud distributed
-- Decoupling
----
-
-## Intent
-
-Aggregate calls to microservices in a single location: the API Gateway. The user makes a single
-call to the API Gateway, and the API Gateway then calls each relevant microservice.
-
-## Class diagram
-
-
-## Applicability
-
-Use the API Gateway pattern when
-
-* you're also using the Microservices pattern and need a single point of aggregation for your
-microservice calls
-
-## Credits
-
-* [microservices.io - API Gateway](http://microservices.io/patterns/apigateway.html)
-* [NGINX - Building Microservices: Using an API Gateway](https://www.nginx.com/blog/building-microservices-using-an-api-gateway/)
diff --git a/api-gateway/api-gateway-service/pom.xml b/api-gateway/api-gateway-service/pom.xml
deleted file mode 100644
index 744023e900c2..000000000000
--- a/api-gateway/api-gateway-service/pom.xml
+++ /dev/null
@@ -1,88 +0,0 @@
-
-
-
-
- api-gateway
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
- api-gateway-service
- jar
-
-
- org.springframework
- spring-webmvc
-
-
- org.springframework.boot
- spring-boot-starter-web
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
- org.mockito
- mockito-core
- test
-
-
-
-
-
-
- org.springframework.boot
- spring-boot-maven-plugin
-
-
-
- repackage
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.api.gateway.App
-
-
-
-
-
-
-
-
-
diff --git a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ApiGateway.java b/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ApiGateway.java
deleted file mode 100644
index fbb8bdfd158b..000000000000
--- a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ApiGateway.java
+++ /dev/null
@@ -1,67 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.api.gateway;
-
-import javax.annotation.Resource;
-import org.springframework.web.bind.annotation.RequestMapping;
-import org.springframework.web.bind.annotation.RequestMethod;
-import org.springframework.web.bind.annotation.RestController;
-
-/**
- * The ApiGateway aggregates calls to microservices based on the needs of the individual clients.
- */
-@RestController
-public class ApiGateway {
-
- @Resource
- private ImageClient imageClient;
-
- @Resource
- private PriceClient priceClient;
-
- /**
- * Retrieves product information that desktop clients need.
- *
- * @return Product information for clients on a desktop
- */
- @RequestMapping(path = "/desktop", method = RequestMethod.GET)
- public DesktopProduct getProductDesktop() {
- var desktopProduct = new DesktopProduct();
- desktopProduct.setImagePath(imageClient.getImagePath());
- desktopProduct.setPrice(priceClient.getPrice());
- return desktopProduct;
- }
-
- /**
- * Retrieves product information that mobile clients need.
- *
- * @return Product information for clients on a mobile device
- */
- @RequestMapping(path = "/mobile", method = RequestMethod.GET)
- public MobileProduct getProductMobile() {
- var mobileProduct = new MobileProduct();
- mobileProduct.setPrice(priceClient.getPrice());
- return mobileProduct;
- }
-}
diff --git a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/App.java b/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/App.java
deleted file mode 100644
index 1d72aaaece37..000000000000
--- a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/App.java
+++ /dev/null
@@ -1,64 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.api.gateway;
-
-import org.springframework.boot.SpringApplication;
-import org.springframework.boot.autoconfigure.SpringBootApplication;
-
-/**
- * With the Microservices pattern, a client may need data from multiple different microservices. If
- * the client called each microservice directly, that could contribute to longer load times, since
- * the client would have to make a network request for each microservice called. Moreover, having
- * the client call each microservice directly ties the client to that microservice - if the internal
- * implementations of the microservices change (for example, if two microservices are combined
- * sometime in the future) or if the location (host and port) of a microservice changes, then every
- * client that makes use of those microservices must be updated.
- *
- * The intent of the API Gateway pattern is to alleviate some of these issues. In the API
- * Gateway pattern, an additional entity (the API Gateway) is placed between the client and the
- * microservices. The job of the API Gateway is to aggregate the calls to the microservices. Rather
- * than the client calling each microservice individually, the client calls the API Gateway a single
- * time. The API Gateway then calls each of the microservices that the client needs.
- *
- *
This implementation shows what the API Gateway pattern could look like for an e-commerce
- * site. The {@link ApiGateway} makes calls to the Image and Price microservices using the {@link
- * ImageClientImpl} and {@link PriceClientImpl} respectively. Customers viewing the site on a
- * desktop device can see both price information and an image of a product, so the {@link
- * ApiGateway} calls both of the microservices and aggregates the data in the {@link DesktopProduct}
- * model. However, mobile users only see price information; they do not see a product image. For
- * mobile users, the {@link ApiGateway} only retrieves price information, which it uses to populate
- * the {@link MobileProduct}.
- */
-@SpringBootApplication
-public class App {
-
- /**
- * Program entry point.
- *
- * @param args command line args
- */
- public static void main(String[] args) {
- SpringApplication.run(App.class, args);
- }
-}
diff --git a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java b/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java
deleted file mode 100644
index 2f790bef5d07..000000000000
--- a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/DesktopProduct.java
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.api.gateway;
-
-/**
- * Encapsulates all of the information that a desktop client needs to display a product.
- */
-public class DesktopProduct {
- /**
- * The price of the product.
- */
- private String price;
-
- /**
- * The path to the image of the product.
- */
- private String imagePath;
-
- public String getPrice() {
- return price;
- }
-
- public void setPrice(String price) {
- this.price = price;
- }
-
- public String getImagePath() {
- return imagePath;
- }
-
- public void setImagePath(String imagePath) {
- this.imagePath = imagePath;
- }
-}
diff --git a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java b/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java
deleted file mode 100644
index 52dd065ffc35..000000000000
--- a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/ImageClientImpl.java
+++ /dev/null
@@ -1,60 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.api.gateway;
-
-import java.io.IOException;
-import java.net.URI;
-import java.net.http.HttpClient;
-import java.net.http.HttpRequest;
-import java.net.http.HttpResponse.BodyHandlers;
-import org.springframework.stereotype.Component;
-
-/**
- * An adapter to communicate with the Image microservice.
- */
-@Component
-public class ImageClientImpl implements ImageClient {
- /**
- * Makes a simple HTTP Get request to the Image microservice.
- *
- * @return The path to the image
- */
- @Override
- public String getImagePath() {
- var httpClient = HttpClient.newHttpClient();
- var httpGet = HttpRequest.newBuilder()
- .GET()
- .uri(URI.create("http://localhost:50005/image-path"))
- .build();
-
- try {
- var httpResponse = httpClient.send(httpGet, BodyHandlers.ofString());
- return httpResponse.body();
- } catch (IOException | InterruptedException e) {
- e.printStackTrace();
- }
-
- return null;
- }
-}
diff --git a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java b/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java
deleted file mode 100644
index 0dc44a51bced..000000000000
--- a/api-gateway/api-gateway-service/src/main/java/com/iluwatar/api/gateway/PriceClientImpl.java
+++ /dev/null
@@ -1,60 +0,0 @@
-/*
- * The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-package com.iluwatar.api.gateway;
-
-import java.io.IOException;
-import java.net.URI;
-import java.net.http.HttpClient;
-import java.net.http.HttpRequest;
-import java.net.http.HttpResponse.BodyHandlers;
-import org.springframework.stereotype.Component;
-
-/**
- * An adapter to communicate with the Price microservice.
- */
-@Component
-public class PriceClientImpl implements PriceClient {
- /**
- * Makes a simple HTTP Get request to the Price microservice.
- *
- * @return The price of the product
- */
- @Override
- public String getPrice() {
- var httpClient = HttpClient.newHttpClient();
- var httpGet = HttpRequest.newBuilder()
- .GET()
- .uri(URI.create("http://localhost:50006/price"))
- .build();
-
- try {
- var httpResponse = httpClient.send(httpGet, BodyHandlers.ofString());
- return httpResponse.body();
- } catch (IOException | InterruptedException e) {
- e.printStackTrace();
- }
-
- return null;
- }
-}
diff --git a/api-gateway/api-gateway-service/src/main/resources/application.properties b/api-gateway/api-gateway-service/src/main/resources/application.properties
deleted file mode 100644
index f9e29f5a7234..000000000000
--- a/api-gateway/api-gateway-service/src/main/resources/application.properties
+++ /dev/null
@@ -1,23 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-server.port=50004
\ No newline at end of file
diff --git a/api-gateway/image-microservice/pom.xml b/api-gateway/image-microservice/pom.xml
deleted file mode 100644
index 27ef343afabc..000000000000
--- a/api-gateway/image-microservice/pom.xml
+++ /dev/null
@@ -1,83 +0,0 @@
-
-
-
-
- api-gateway
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
- image-microservice
- jar
-
-
- org.springframework
- spring-webmvc
-
-
- org.springframework.boot
- spring-boot-starter-web
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
-
-
-
-
- org.springframework.boot
- spring-boot-maven-plugin
-
-
-
- repackage
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.image.microservice.ImageApplication
-
-
-
-
-
-
-
-
-
diff --git a/api-gateway/image-microservice/src/main/resources/application.properties b/api-gateway/image-microservice/src/main/resources/application.properties
deleted file mode 100644
index da11b3c3db44..000000000000
--- a/api-gateway/image-microservice/src/main/resources/application.properties
+++ /dev/null
@@ -1,24 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-
-server.port=50005
\ No newline at end of file
diff --git a/api-gateway/pom.xml b/api-gateway/pom.xml
deleted file mode 100644
index 63a98699677c..000000000000
--- a/api-gateway/pom.xml
+++ /dev/null
@@ -1,42 +0,0 @@
-
-
-
-
- java-design-patterns
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
- api-gateway
- pom
-
- image-microservice
- price-microservice
- api-gateway-service
-
-
diff --git a/api-gateway/price-microservice/pom.xml b/api-gateway/price-microservice/pom.xml
deleted file mode 100644
index e7b144c5895c..000000000000
--- a/api-gateway/price-microservice/pom.xml
+++ /dev/null
@@ -1,85 +0,0 @@
-
-
-
-
- api-gateway
- com.iluwatar
- 1.23.0-SNAPSHOT
-
-
- 4.0.0
- price-microservice
- jar
-
-
-
- org.springframework
- spring-webmvc
-
-
- org.springframework.boot
- spring-boot-starter-web
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
-
-
-
-
- org.springframework.boot
- spring-boot-maven-plugin
-
-
-
- repackage
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.price.microservices.PriceApplication
-
-
-
-
-
-
-
-
-
diff --git a/api-gateway/price-microservice/src/main/resources/application.properties b/api-gateway/price-microservice/src/main/resources/application.properties
deleted file mode 100644
index 139fa222314e..000000000000
--- a/api-gateway/price-microservice/src/main/resources/application.properties
+++ /dev/null
@@ -1,24 +0,0 @@
-#
-# The MIT License
-# Copyright © 2014-2019 Ilkka Seppälä
-#
-# Permission is hereby granted, free of charge, to any person obtaining a copy
-# of this software and associated documentation files (the "Software"), to deal
-# in the Software without restriction, including without limitation the rights
-# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-# copies of the Software, and to permit persons to whom the Software is
-# furnished to do so, subject to the following conditions:
-#
-# The above copyright notice and this permission notice shall be included in
-# all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-# THE SOFTWARE.
-#
-
-server.port=50006
\ No newline at end of file
diff --git a/arrange-act-assert/README.md b/arrange-act-assert/README.md
new file mode 100644
index 000000000000..584d8601a23e
--- /dev/null
+++ b/arrange-act-assert/README.md
@@ -0,0 +1,167 @@
+---
+title: "Arrange/Act/Assert Pattern in Java: Enhance Testing Clarity and Simplicity"
+shortTitle: Arrange/Act/Assert
+description: "Learn how to use the Arrange/Act/Assert pattern to structure your unit tests in Java. Improve readability and maintainability of your code with clear testing phases."
+category: Testing
+language: en
+tag:
+ - Code simplification
+ - Isolation
+ - Testing
+---
+
+## Also known as
+
+* Given/When/Then
+
+## Intent of Arrange/Act/Assert Design Pattern
+
+The Arrange/Act/Assert pattern is essential in unit testing in Java. This testing method structures unit tests clearly by dividing them into three distinct sections: setup (Arrange), execution (Act), and verification (Assert).
+
+## Detailed Explanation of Arrange/Act/Assert Pattern with Real-World Examples
+
+Real-world example
+
+> Imagine you are organizing a small event. To ensure everything runs smoothly, you follow a pattern similar to Arrange/Act/Assert:
+>
+> 1. **Arrange**: You set up the venue, prepare the guest list, arrange seating, and organize the catering.
+> 2. **Act**: You conduct the event according to the plan, welcoming guests, serving food, and following the schedule.
+> 3. **Assert**: After the event, you evaluate its success by checking guest feedback, ensuring all tasks were completed, and reviewing if everything went as planned.
+>
+> This clear separation of preparation, execution, and evaluation helps ensure the event is well-organized and successful, mirroring the structured approach of the Arrange/Act/Assert pattern in software testing.
+
+In plain words
+
+> Arrange/Act/Assert is a testing pattern that organizes tests into three clear steps for easy maintenance.
+
+WikiWikiWeb says
+
+> Arrange/Act/Assert is a pattern for arranging and formatting code in UnitTest methods.
+
+Flowchart
+
+
+
+## Programmatic Example of Arrange/Act/Assert Pattern in Java
+
+We need to write comprehensive and clear unit test suite for a class. Using the Arrange/Act/Assert pattern in Java testing ensures clarity.
+
+Let's first introduce our `Cash` class to be unit tested.
+
+```java
+public class Cash {
+
+ private int amount;
+
+ Cash(int amount) {
+ this.amount = amount;
+ }
+
+ void plus(int addend) {
+ amount += addend;
+ }
+
+ boolean minus(int subtrahend) {
+ if (amount >= subtrahend) {
+ amount -= subtrahend;
+ return true;
+ } else {
+ return false;
+ }
+ }
+
+ int count() {
+ return amount;
+ }
+}
+```
+
+Then we write our unit tests according to Arrange/Act/Assert pattern. Notice the clearly separated steps for each unit test.
+
+```java
+class CashAAATest {
+
+ @Test
+ void testPlus() {
+ //Arrange
+ var cash = new Cash(3);
+ //Act
+ cash.plus(4);
+ //Assert
+ assertEquals(7, cash.count());
+ }
+
+ @Test
+ void testMinus() {
+ //Arrange
+ var cash = new Cash(8);
+ //Act
+ var result = cash.minus(5);
+ //Assert
+ assertTrue(result);
+ assertEquals(3, cash.count());
+ }
+
+ @Test
+ void testInsufficientMinus() {
+ //Arrange
+ var cash = new Cash(1);
+ //Act
+ var result = cash.minus(6);
+ //Assert
+ assertFalse(result);
+ assertEquals(1, cash.count());
+ }
+
+ @Test
+ void testUpdate() {
+ //Arrange
+ var cash = new Cash(5);
+ //Act
+ cash.plus(6);
+ var result = cash.minus(3);
+ //Assert
+ assertTrue(result);
+ assertEquals(8, cash.count());
+ }
+}
+```
+
+## When to Use the Arrange/Act/Assert Pattern in Java
+
+Use Arrange/Act/Assert pattern when
+
+* Unit testing, especially within the context of TDD and BDD
+* Anywhere clarity and structure are needed in test cases
+
+## Real-World Applications of Arrange/Act/Assert Pattern in Java
+
+* This pattern is particularly useful when practicing TDD and/or BDD methodologies in Java.
+* Utilized in various programming languages and testing frameworks, such as JUnit (Java), NUnit (.NET), and xUnit frameworks.
+
+## Benefits and Trade-offs of Arrange/Act/Assert Pattern
+
+Benefits:
+
+* Improved readability of tests by clearly separating the setup, action, and verification steps.
+* Easier maintenance and understanding of tests, as each test is structured in a predictable way.
+* Facilitates debugging by isolating test failures to specific phases within the test.
+
+Trade-offs:
+
+* May introduce redundancy in tests, as similar arrangements may be repeated across tests.
+* Some complex tests might not fit neatly into this structure, requiring additional context or setup outside these three phases.
+
+## Related Java Design Patterns
+
+* [Page Object](https://java-design-patterns.com/patterns/page-object/): A pattern for organizing UI tests that can be used in conjunction with Arrange/Act/Assert.
+
+## References and Credits
+
+* [The Art of Unit Testing: with examples in C#](https://amzn.to/49IbdwO)
+* [Test Driven Development: By Example](https://amzn.to/3wEwKbF)
+* [Unit Testing Principles, Practices, and Patterns: Effective testing styles, patterns, and reliable automation for unit testing, mocking, and integration testing with examples in C#](https://amzn.to/4ayjpiM)
+* [xUnit Test Patterns: Refactoring Test Code](https://amzn.to/4dHGDpm)
+* [Arrange, Act, Assert: What is AAA Testing?](https://blog.ncrunch.net/post/arrange-act-assert-aaa-testing.aspx)
+* [Bill Wake: 3A – Arrange, Act, Assert (NCrunch)](https://xp123.com/articles/3a-arrange-act-assert/)
+* [GivenWhenThen (Martin Fowler)](https://martinfowler.com/bliki/GivenWhenThen.html)
diff --git a/arrange-act-assert/etc/arrange-act-assert-flowchart.png b/arrange-act-assert/etc/arrange-act-assert-flowchart.png
new file mode 100644
index 000000000000..8b7615352523
Binary files /dev/null and b/arrange-act-assert/etc/arrange-act-assert-flowchart.png differ
diff --git a/arrange-act-assert/etc/arrange-act-assert.urm.puml b/arrange-act-assert/etc/arrange-act-assert.urm.puml
new file mode 100644
index 000000000000..4b22d2a4e4bb
--- /dev/null
+++ b/arrange-act-assert/etc/arrange-act-assert.urm.puml
@@ -0,0 +1,11 @@
+@startuml
+package com.iluwatar.arrangeactassert {
+ class Cash {
+ - amount : int
+ ~ Cash(amount : int)
+ ~ count() : int
+ ~ minus(subtrahend : int) : boolean
+ ~ plus(addend : int)
+ }
+}
+@enduml
\ No newline at end of file
diff --git a/arrange-act-assert/pom.xml b/arrange-act-assert/pom.xml
new file mode 100644
index 000000000000..6b8ba1b2d490
--- /dev/null
+++ b/arrange-act-assert/pom.xml
@@ -0,0 +1,43 @@
+
+
+
+
+ java-design-patterns
+ com.iluwatar
+ 1.26.0-SNAPSHOT
+
+ 4.0.0
+ arrange-act-assert
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+
diff --git a/arrange-act-assert/src/main/java/com/iluwatar/arrangeactassert/Cash.java b/arrange-act-assert/src/main/java/com/iluwatar/arrangeactassert/Cash.java
new file mode 100644
index 000000000000..0c31b1f89f44
--- /dev/null
+++ b/arrange-act-assert/src/main/java/com/iluwatar/arrangeactassert/Cash.java
@@ -0,0 +1,57 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.arrangeactassert;
+
+import lombok.AllArgsConstructor;
+
+/**
+ * Arrange/Act/Assert (AAA) is a unit test pattern. In this simple example, we have a ({@link Cash})
+ * object for plus, minus and counting amount.
+ */
+@AllArgsConstructor
+public class Cash {
+
+ private int amount;
+
+ // plus
+ void plus(int addend) {
+ amount += addend;
+ }
+
+ // minus
+ boolean minus(int subtrahend) {
+ if (amount >= subtrahend) {
+ amount -= subtrahend;
+ return true;
+ } else {
+ return false;
+ }
+ }
+
+ // count
+ int count() {
+ return amount;
+ }
+}
diff --git a/arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAAATest.java b/arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAAATest.java
new file mode 100644
index 000000000000..ebb261277080
--- /dev/null
+++ b/arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAAATest.java
@@ -0,0 +1,103 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.arrangeactassert;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Arrange/Act/Assert (AAA) is a pattern for organizing unit tests. It is a way to structure your
+ * tests, so they're easier to read, maintain and enhance.
+ *
+ *
It breaks tests down into three clear and distinct steps:
+ *
+ *
1. Arrange: Perform the setup and initialization required for the test.
+ *
+ *
2. Act: Take action(s) required for the test.
+ *
+ *
3. Assert: Verify the outcome(s) of the test.
+ *
+ *
This pattern has several significant benefits. It creates a clear separation between a test's
+ * setup, operations, and results. This structure makes the code easier to read and understand. If
+ * you place the steps in order and format your code to separate them, you can scan a test and
+ * quickly comprehend what it does.
+ *
+ *
It also enforces a certain degree of discipline when you write your tests. You have to think
+ * clearly about the three steps your test will perform. But it makes tests more natural to write at
+ * the same time since you already have an outline.
+ *
+ *
In ({@link CashAAATest}) we have four test methods. Each of them has only one reason to change
+ * and one reason to fail. In a large and complicated code base, tests that honor the single
+ * responsibility principle are much easier to troubleshoot.
+ */
+class CashAAATest {
+
+ @Test
+ void testPlus() {
+ // Arrange
+ var cash = new Cash(3);
+ // Act
+ cash.plus(4);
+ // Assert
+ assertEquals(7, cash.count());
+ }
+
+ @Test
+ void testMinus() {
+ // Arrange
+ var cash = new Cash(8);
+ // Act
+ var result = cash.minus(5);
+ // Assert
+ assertTrue(result);
+ assertEquals(3, cash.count());
+ }
+
+ @Test
+ void testInsufficientMinus() {
+ // Arrange
+ var cash = new Cash(1);
+ // Act
+ var result = cash.minus(6);
+ // Assert
+ assertFalse(result);
+ assertEquals(1, cash.count());
+ }
+
+ @Test
+ void testUpdate() {
+ // Arrange
+ var cash = new Cash(5);
+ // Act
+ cash.plus(6);
+ var result = cash.minus(3);
+ // Assert
+ assertTrue(result);
+ assertEquals(8, cash.count());
+ }
+}
diff --git a/arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAntiAAATest.java b/arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAntiAAATest.java
new file mode 100644
index 000000000000..5756822516b8
--- /dev/null
+++ b/arrange-act-assert/src/test/java/com/iluwatar/arrangeactassert/CashAntiAAATest.java
@@ -0,0 +1,60 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.arrangeactassert;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * ({@link CashAAATest}) is an anti-example of AAA pattern. This test is functionally correct, but
+ * with the addition of a new feature, it needs refactoring. There are an awful lot of steps in that
+ * test method, but it verifies the class' important behavior in just eleven lines. It violates the
+ * single responsibility principle. If this test method failed after a small code change, it might
+ * take some digging to discover why.
+ */
+class CashAntiAAATest {
+
+ @Test
+ void testCash() {
+ // initialize
+ var cash = new Cash(3);
+ // test plus
+ cash.plus(4);
+ assertEquals(7, cash.count());
+ // test minus
+ cash = new Cash(8);
+ assertTrue(cash.minus(5));
+ assertEquals(3, cash.count());
+ assertFalse(cash.minus(6));
+ assertEquals(3, cash.count());
+ // test update
+ cash.plus(5);
+ assertTrue(cash.minus(5));
+ assertEquals(3, cash.count());
+ }
+}
diff --git a/async-method-invocation/README.md b/async-method-invocation/README.md
index d1bda1a528cd..519152e1268c 100644
--- a/async-method-invocation/README.md
+++ b/async-method-invocation/README.md
@@ -1,31 +1,217 @@
---
-layout: pattern
-title: Async Method Invocation
-folder: async-method-invocation
-permalink: /patterns/async-method-invocation/
-categories: Concurrency
-tags:
- - Reactive
+title: "Async Method Invocation Pattern in Java: Elevate Performance with Asynchronous Programming"
+shortTitle: Async Method Invocation
+description: "Learn about the Async Method Invocation pattern in Java for asynchronous method calls, enhancing concurrency, scalability, and responsiveness in your applications. Explore real-world examples and code implementations."
+category: Concurrency
+language: en
+tag:
+ - Asynchronous
+ - Decoupling
+ - Reactive
+ - Scalability
+ - Thread management
---
-## Intent
-Asynchronous method invocation is pattern where the calling thread
-is not blocked while waiting results of tasks. The pattern provides parallel
-processing of multiple independent tasks and retrieving the results via
-callbacks or waiting until everything is done.
+## Also known as
-# Class diagram
-
+* Asynchronous Procedure Call
-## Applicability
-Use async method invocation pattern when
+## Intent of Async Method Invocation Design Pattern
-* you have multiple independent tasks that can run in parallel
-* you need to improve the performance of a group of sequential tasks
-* you have limited amount of processing capacity or long running tasks and the
- caller should not wait the tasks to be ready
+The Async Method Invocation pattern is designed to enhance concurrency by allowing methods to be called asynchronously. This pattern helps in executing parallel tasks, reducing wait times, and improving system throughput.
-## Real world examples
+## Detailed Explanation of Async Method Invocation Pattern with Real-World Examples
-* [FutureTask](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/FutureTask.html), [CompletableFuture](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html) and [ExecutorService](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ExecutorService.html) (Java)
-* [Task-based Asynchronous Pattern](https://msdn.microsoft.com/en-us/library/hh873175.aspx) (.NET)
+Real-world example
+
+> Asynchronous method invocation enables non-blocking operations, allowing multiple processes to run concurrently. This pattern is particularly useful in applications requiring high scalability and performance, such as web servers and microservices.
+>
+> In the context of space rockets, an analogous example of the Async Method Invocation pattern can be seen in the communication between the mission control center and the onboard systems of the rocket. When mission control sends a command to the rocket to adjust its trajectory or perform a system check, they do not wait idly for the rocket to complete the task and report back. Instead, mission control continues to monitor other aspects of the mission and manage different tasks. The rocket executes the command asynchronously and sends a status update or result back to mission control once the operation is complete. This allows mission control to efficiently manage multiple concurrent operations without being blocked by any single task, similar to how asynchronous method invocation works in software systems.
+
+In plain words
+
+> Asynchronous method invocation starts task processing and returns immediately before the task is ready. The results of the task processing are returned to the caller later.
+
+Wikipedia says
+
+> In multithreaded computer programming, asynchronous method invocation (AMI), also known as asynchronous method calls or the asynchronous pattern is a design pattern in which the call site is not blocked while waiting for the called code to finish. Instead, the calling thread is notified when the reply arrives. Polling for a reply is an undesired option.
+
+Sequence diagram
+
+
+
+## Programmatic Example of Async Method Invocation Pattern in Java
+
+Consider a scenario where multiple tasks need to be executed simultaneously. Using the Async Method Invocation pattern, you can initiate these tasks without waiting for each to complete, thus optimizing resource usage and reducing latency.
+
+In this example, we are launching space rockets and deploying lunar rovers.
+
+The application demonstrates the async method invocation pattern. The key parts of the pattern are`AsyncResult` which is an intermediate container for an asynchronously evaluated value, `AsyncCallback` which can be provided to be executed on task completion and `AsyncExecutor` that manages the execution of the async tasks.
+
+```java
+public interface AsyncResult {
+ boolean isCompleted();
+
+ T getValue() throws ExecutionException;
+
+ void await() throws InterruptedException;
+}
+```
+
+```java
+public interface AsyncCallback {
+ void onComplete(T value);
+
+ void onError(Exception ex);
+}
+```
+
+```java
+public interface AsyncExecutor {
+ AsyncResult startProcess(Callable task);
+
+ AsyncResult startProcess(Callable task, AsyncCallback callback);
+
+ T endProcess(AsyncResult asyncResult) throws ExecutionException, InterruptedException;
+}
+```
+
+`ThreadAsyncExecutor` is an implementation of `AsyncExecutor`. Some of its key parts are highlighted next.
+
+```java
+public class ThreadAsyncExecutor implements AsyncExecutor {
+
+ @Override
+ public AsyncResult startProcess(Callable task) {
+ return startProcess(task, null);
+ }
+
+ @Override
+ public AsyncResult startProcess(Callable task, AsyncCallback callback) {
+ var result = new CompletableResult<>(callback);
+ new Thread(
+ () -> {
+ try {
+ result.setValue(task.call());
+ } catch (Exception ex) {
+ result.setException(ex);
+ }
+ },
+ "executor-" + idx.incrementAndGet())
+ .start();
+ return result;
+ }
+
+ @Override
+ public T endProcess(AsyncResult asyncResult)
+ throws ExecutionException, InterruptedException {
+ if (!asyncResult.isCompleted()) {
+ asyncResult.await();
+ }
+ return asyncResult.getValue();
+ }
+}
+```
+
+Then we are ready to launch some rockets to see how everything works together.
+
+```java
+ public static void main(String[] args) throws Exception {
+ // construct a new executor that will run async tasks
+ var executor = new ThreadAsyncExecutor();
+
+ // start few async tasks with varying processing times, two last with callback handlers
+ final var asyncResult1 = executor.startProcess(lazyval(10, 500));
+ final var asyncResult2 = executor.startProcess(lazyval("test", 300));
+ final var asyncResult3 = executor.startProcess(lazyval(50L, 700));
+ final var asyncResult4 = executor.startProcess(lazyval(20, 400),
+ callback("Deploying lunar rover"));
+ final var asyncResult5 =
+ executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
+
+ // emulate processing in the current thread while async tasks are running in their own threads
+ Thread.sleep(350); // Oh boy, we are working hard here
+ log("Mission command is sipping coffee");
+
+ // wait for completion of the tasks
+ final var result1 = executor.endProcess(asyncResult1);
+ final var result2 = executor.endProcess(asyncResult2);
+ final var result3 = executor.endProcess(asyncResult3);
+ asyncResult4.await();
+ asyncResult5.await();
+
+ // log the results of the tasks, callbacks log immediately when complete
+ log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result1));
+ log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result2));
+ log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result3));
+}
+```
+
+Here's the program console output.
+
+```
+21:47:08.227[executor-2]INFO com.iluwatar.async.method.invocation.App-Space rocket launched successfully
+21:47:08.269[main]INFO com.iluwatar.async.method.invocation.App-Mission command is sipping coffee
+21:47:08.318[executor-4]INFO com.iluwatar.async.method.invocation.App-Space rocket<20>launched successfully
+21:47:08.335[executor-4]INFO com.iluwatar.async.method.invocation.App-Deploying lunar rover<20>
+21:47:08.414[executor-1]INFO com.iluwatar.async.method.invocation.App-Space rocket<10>launched successfully
+21:47:08.519[executor-5]INFO com.iluwatar.async.method.invocation.App-Space rocket launched successfully
+21:47:08.519[executor-5]INFO com.iluwatar.async.method.invocation.App-Deploying lunar rover
+21:47:08.616[executor-3]INFO com.iluwatar.async.method.invocation.App-Space rocket<50>launched successfully
+21:47:08.617[main]INFO com.iluwatar.async.method.invocation.App-Space rocket<10>launch complete
+21:47:08.617[main]INFO com.iluwatar.async.method.invocation.App-Space rocket launch complete
+21:47:08.618[main]INFO com.iluwatar.async.method.invocation.App-Space rocket<50>launch complete
+```
+
+## When to Use the Async Method Invocation Pattern in Java
+
+This pattern is ideal for applications needing to manage multiple parallel tasks efficiently. It is commonly used in scenarios such as handling background processes, improving user interface responsiveness, and managing asynchronous data processing.
+
+Use the async method invocation pattern when
+
+* When operations do not need to complete before proceeding with the next steps in a program.
+* For tasks that are resource-intensive or time-consuming, such as IO operations, network requests, or complex computations, where making the operation synchronous would significantly impact performance or user experience.
+* In GUI applications to prevent freezing or unresponsiveness during long-running tasks.
+* In web applications for non-blocking IO operations.
+
+## Real-World Applications of Async Method Invocation Pattern in Java
+
+Many modern applications leverage the Async Method Invocation pattern, including web servers handling concurrent requests, microservices architectures, and systems requiring intensive background processing.
+
+* Web servers handling HTTP requests asynchronously to improve throughput and reduce latency.
+* Desktop and mobile applications using background threads to perform time-consuming operations without blocking the user interface.
+* Microservices architectures where services perform asynchronous communications via messaging queues or event streams.
+* [FutureTask](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/FutureTask.html)
+* [CompletableFuture](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html)
+* [ExecutorService](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ExecutorService.html)
+* [Task-based Asynchronous Pattern](https://msdn.microsoft.com/en-us/library/hh873175.aspx)
+
+## Benefits and Trade-offs of Async Method Invocation Pattern
+
+While this pattern offers significant performance benefits, it also introduces complexity in error handling and resource management. Proper implementation is essential to avoid potential pitfalls such as race conditions and deadlocks.
+
+Benefits:
+
+* Improved Responsiveness: The main thread or application flow remains unblocked, improving the user experience in GUI applications and overall responsiveness.
+* Better Resource Utilization: By enabling parallel execution, system resources (like CPU and IO) are utilized more efficiently, potentially improving the application's throughput.
+* Scalability: Easier to scale applications, as tasks can be distributed across available resources more effectively.
+
+Trade-offs:
+
+* Complexity: Introducing asynchronous operations can complicate the codebase, making it more challenging to understand, debug, and maintain.
+* Resource Management: Requires careful management of threads or execution contexts, which can introduce overhead and potential resource exhaustion issues.
+* Error Handling: Asynchronous operations can make error handling more complex, as exceptions may occur in different threads or at different times.
+
+## Related Java Design Patterns
+
+The Async Method Invocation pattern often works well with other design patterns like the Command Pattern for encapsulating requests, the Observer Pattern for event handling, and the Promise Pattern for managing asynchronous results.
+
+* [Command](https://java-design-patterns.com/patterns/command/): Asynchronous method invocation can be used to implement the Command pattern, where commands are executed asynchronously.
+* [Observer](https://java-design-patterns.com/patterns/observer/): Asynchronous method invocation can be used to notify observers asynchronously when a subject's state changes.
+* [Promise](https://java-design-patterns.com/patterns/promise/): The AsyncResult interface can be considered a form of Promise, representing a value that may not be available yet.
+
+## References and Credits
+
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3Ti1N4f)
+* [Effective Java](https://amzn.to/4cGk2Jz)
+* [Java Concurrency in Practice](https://amzn.to/4ab97VU)
diff --git a/async-method-invocation/etc/async-method-invocation-sequence-diagram.png b/async-method-invocation/etc/async-method-invocation-sequence-diagram.png
new file mode 100644
index 000000000000..28420d783379
Binary files /dev/null and b/async-method-invocation/etc/async-method-invocation-sequence-diagram.png differ
diff --git a/async-method-invocation/etc/async-method-invocation.ucls b/async-method-invocation/etc/async-method-invocation.ucls
deleted file mode 100644
index f2e189eaeae0..000000000000
--- a/async-method-invocation/etc/async-method-invocation.ucls
+++ /dev/null
@@ -1,85 +0,0 @@
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
\ No newline at end of file
diff --git a/async-method-invocation/etc/async-method-invocation.urm.png b/async-method-invocation/etc/async-method-invocation.urm.png
new file mode 100644
index 000000000000..898c1e199bda
Binary files /dev/null and b/async-method-invocation/etc/async-method-invocation.urm.png differ
diff --git a/async-method-invocation/etc/async-method-invocation.urm.puml b/async-method-invocation/etc/async-method-invocation.urm.puml
index 6f5d0b27f9d4..d44665081856 100644
--- a/async-method-invocation/etc/async-method-invocation.urm.puml
+++ b/async-method-invocation/etc/async-method-invocation.urm.puml
@@ -9,7 +9,8 @@ package com.iluwatar.async.method.invocation {
+ main(args : String[]) {static}
}
interface AsyncCallback {
- + onComplete(T, Optional) {abstract}
+ + onComplete(T) {abstract}
+ + onError(Exception) {abstract}
}
interface AsyncExecutor {
+ endProcess(AsyncResult) : T {abstract}
@@ -32,7 +33,7 @@ package com.iluwatar.async.method.invocation {
~ COMPLETED : int {static}
~ FAILED : int {static}
~ RUNNING : int {static}
- ~ callback : Optional>
+ ~ callback : AsyncCallback
~ exception : Exception
~ lock : Object
~ state : int
@@ -40,12 +41,15 @@ package com.iluwatar.async.method.invocation {
~ CompletableResult(callback : AsyncCallback)
+ await()
+ getValue() : T
+ ~ hasCallback() : boolean
+ isCompleted() : boolean
~ setException(exception : Exception)
~ setValue(value : T)
}
}
+ThreadAsyncExecutor ..|> AsyncCallback
+ThreadAsyncExecutor ..|> AsyncResult
+ThreadAsyncExecutor ..|> AsyncExecutor
CompletableResult ..+ ThreadAsyncExecutor
-ThreadAsyncExecutor ..|> AsyncExecutor
-CompletableResult ..|> AsyncResult
-@enduml
\ No newline at end of file
+CompletableResult ..|> AsyncResult
+@enduml
diff --git a/async-method-invocation/pom.xml b/async-method-invocation/pom.xml
index 46aa9d354a0f..d9ddd918c8e9 100644
--- a/async-method-invocation/pom.xml
+++ b/async-method-invocation/pom.xml
@@ -1,64 +1,75 @@
-
-
-
- 4.0.0
-
- com.iluwatar
- java-design-patterns
- 1.23.0-SNAPSHOT
-
- async-method-invocation
-
-
- org.junit.jupiter
- junit-jupiter-engine
- test
-
-
- org.mockito
- mockito-core
- test
-
-
- junit
- junit
- test
-
-
-
-
-
- org.apache.maven.plugins
- maven-assembly-plugin
-
-
-
-
-
- com.iluwatar.async.method.invocation.App
-
-
-
-
-
-
-
-
+
+
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+ async-method-invocation
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+ org.mockito
+ mockito-core
+ test
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.async.method.invocation.App
+
+
+
+
+
+
+
+
diff --git a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java
index 40c186704cd7..ec3beed3be4d 100644
--- a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java
+++ b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,23 +22,23 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.async.method.invocation;
import java.util.concurrent.Callable;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
/**
- * This application demonstrates the async method invocation pattern. Key parts of the pattern are
- * AsyncResult which is an intermediate container for an asynchronously evaluated
+ * In this example, we are launching space rockets and deploying lunar rovers.
+ *
+ * The application demonstrates the async method invocation pattern. The key parts of the pattern
+ * are AsyncResult which is an intermediate container for an asynchronously evaluated
* value, AsyncCallback which can be provided to be executed on task completion and
* AsyncExecutor that manages the execution of the async tasks.
*
- *
The main method shows example flow of async invocations. The main thread starts multiple
- * tasks with variable durations and then continues its own work. When the main thread has done it's
- * job it collects the results of the async tasks. Two of the tasks are handled with callbacks,
- * meaning the callbacks are executed immediately when the tasks complete.
+ *
The main method shows example flow of async invocations. The main thread starts multiple tasks
+ * with variable durations and then continues its own work. When the main thread has done it's job
+ * it collects the results of the async tasks. Two of the tasks are handled with callbacks, meaning
+ * the callbacks are executed immediately when the tasks complete.
*
*
Noteworthy difference of thread usage between the async results and callbacks is that the
* async results are collected in the main thread but the callbacks are executed within the worker
@@ -55,13 +57,12 @@
* @see java.util.concurrent.CompletableFuture
* @see java.util.concurrent.ExecutorService
*/
+@Slf4j
public class App {
- private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
+ private static final String ROCKET_LAUNCH_LOG_PATTERN = "Space rocket <%s> launched successfully";
- /**
- * Program entry point.
- */
+ /** Program entry point. */
public static void main(String[] args) throws Exception {
// construct a new executor that will run async tasks
var executor = new ThreadAsyncExecutor();
@@ -70,13 +71,14 @@ public static void main(String[] args) throws Exception {
final var asyncResult1 = executor.startProcess(lazyval(10, 500));
final var asyncResult2 = executor.startProcess(lazyval("test", 300));
final var asyncResult3 = executor.startProcess(lazyval(50L, 700));
- final var asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Callback result 4"));
+ final var asyncResult4 =
+ executor.startProcess(lazyval(20, 400), callback("Deploying lunar rover"));
final var asyncResult5 =
- executor.startProcess(lazyval("callback", 600), callback("Callback result 5"));
+ executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
// emulate processing in the current thread while async tasks are running in their own threads
- Thread.sleep(350); // Oh boy I'm working hard here
- log("Some hard work done");
+ Thread.sleep(350); // Oh boy, we are working hard here
+ log("Mission command is sipping coffee");
// wait for completion of the tasks
final var result1 = executor.endProcess(asyncResult1);
@@ -86,22 +88,22 @@ public static void main(String[] args) throws Exception {
asyncResult5.await();
// log the results of the tasks, callbacks log immediately when complete
- log("Result 1: " + result1);
- log("Result 2: " + result2);
- log("Result 3: " + result3);
+ log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result1));
+ log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result2));
+ log(String.format(ROCKET_LAUNCH_LOG_PATTERN, result3));
}
/**
* Creates a callable that lazily evaluates to given value with artificial delay.
*
- * @param value value to evaluate
+ * @param value value to evaluate
* @param delayMillis artificial delay in milliseconds
* @return new callable for lazy evaluation
*/
private static Callable lazyval(T value, long delayMillis) {
return () -> {
Thread.sleep(delayMillis);
- log("Task completed with: " + value);
+ log(String.format(ROCKET_LAUNCH_LOG_PATTERN, value));
return value;
};
}
@@ -113,11 +115,15 @@ private static Callable lazyval(T value, long delayMillis) {
* @return new async callback
*/
private static AsyncCallback callback(String name) {
- return (value, ex) -> {
- if (ex.isPresent()) {
- log(name + " failed: " + ex.map(Exception::getMessage).orElse(""));
- } else {
- log(name + ": " + value);
+ return new AsyncCallback<>() {
+ @Override
+ public void onComplete(T value) {
+ log(name + " <" + value + ">");
+ }
+
+ @Override
+ public void onError(Exception ex) {
+ log(name + " failed: " + ex.getMessage());
}
};
}
diff --git a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncCallback.java b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncCallback.java
index 22b36134ff97..2dfbaf9a188a 100644
--- a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncCallback.java
+++ b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncCallback.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,11 +22,8 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.async.method.invocation;
-import java.util.Optional;
-
/**
* AsyncCallback interface.
*
@@ -33,10 +32,16 @@
public interface AsyncCallback {
/**
- * Complete handler which is executed when async task is completed or fails execution.
+ * Complete handler which is executed when async task is completed.
+ *
+ * @param value the evaluated value from async task
+ */
+ void onComplete(T value);
+
+ /**
+ * Error handler which is executed when async task fails execution.
*
- * @param value the evaluated value from async task, undefined when execution fails
- * @param ex empty value if execution succeeds, some exception if executions fails
+ * @param ex exception which was thrown during async task execution(non-null)
*/
- void onComplete(T value, Optional ex);
+ void onError(Exception ex);
}
diff --git a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncExecutor.java b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncExecutor.java
index 819ffd2377ca..3bae90830098 100644
--- a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncExecutor.java
+++ b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncExecutor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,15 +22,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.async.method.invocation;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
-/**
- * AsyncExecutor interface.
- */
+/** AsyncExecutor interface. */
public interface AsyncExecutor {
/**
@@ -43,7 +42,7 @@ public interface AsyncExecutor {
* Starts processing of an async task. Returns immediately with async result. Executes callback
* when the task is completed.
*
- * @param task task to be executed asynchronously
+ * @param task task to be executed asynchronously
* @param callback callback to be executed on task completion
* @return async result for the task
*/
@@ -55,7 +54,7 @@ public interface AsyncExecutor {
*
* @param asyncResult async result of a task
* @return evaluated value of the completed task
- * @throws ExecutionException if execution has failed, containing the root cause
+ * @throws ExecutionException if execution has failed, containing the root cause
* @throws InterruptedException if the execution is interrupted
*/
T endProcess(AsyncResult asyncResult) throws ExecutionException, InterruptedException;
diff --git a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncResult.java b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncResult.java
index 6aaf233b44f7..3eebdc4e773d 100644
--- a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncResult.java
+++ b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/AsyncResult.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.async.method.invocation;
import java.util.concurrent.ExecutionException;
@@ -43,7 +44,7 @@ public interface AsyncResult {
* Gets the value of completed async task.
*
* @return evaluated value or throws ExecutionException if execution has failed
- * @throws ExecutionException if execution has failed, containing the root cause
+ * @throws ExecutionException if execution has failed, containing the root cause
* @throws IllegalStateException if execution is not completed
*/
T getValue() throws ExecutionException;
diff --git a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutor.java b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutor.java
index 7bdf841716d2..a1261f34184c 100644
--- a/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutor.java
+++ b/async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutor.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,22 +22,16 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.async.method.invocation;
-import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.atomic.AtomicInteger;
-/**
- * Implementation of async executor that creates a new thread for every task.
- */
+/** Implementation of async executor that creates a new thread for every task. */
public class ThreadAsyncExecutor implements AsyncExecutor {
- /**
- * Index for thread naming.
- */
+ /** Index for thread naming. */
private final AtomicInteger idx = new AtomicInteger(0);
@Override
@@ -46,19 +42,22 @@ public AsyncResult startProcess(Callable task) {
@Override
public AsyncResult startProcess(Callable task, AsyncCallback callback) {
var result = new CompletableResult<>(callback);
- new Thread(() -> {
- try {
- result.setValue(task.call());
- } catch (Exception ex) {
- result.setException(ex);
- }
- }, "executor-" + idx.incrementAndGet()).start();
+ new Thread(
+ () -> {
+ try {
+ result.setValue(task.call());
+ } catch (Exception ex) {
+ result.setException(ex);
+ }
+ },
+ "executor-" + idx.incrementAndGet())
+ .start();
return result;
}
@Override
- public T endProcess(AsyncResult asyncResult) throws ExecutionException,
- InterruptedException {
+ public T endProcess(AsyncResult asyncResult)
+ throws ExecutionException, InterruptedException {
if (!asyncResult.isCompleted()) {
asyncResult.await();
}
@@ -80,7 +79,7 @@ private static class CompletableResult implements AsyncResult {
static final int COMPLETED = 3;
final Object lock;
- final Optional> callback;
+ final AsyncCallback callback;
volatile int state = RUNNING;
T value;
@@ -88,7 +87,11 @@ private static class CompletableResult implements AsyncResult {
CompletableResult(AsyncCallback callback) {
this.lock = new Object();
- this.callback = Optional.ofNullable(callback);
+ this.callback = callback;
+ }
+
+ boolean hasCallback() {
+ return callback != null;
}
/**
@@ -100,7 +103,9 @@ private static class CompletableResult implements AsyncResult {
void setValue(T value) {
this.value = value;
this.state = COMPLETED;
- this.callback.ifPresent(ac -> ac.onComplete(value, Optional.empty()));
+ if (hasCallback()) {
+ callback.onComplete(value);
+ }
synchronized (lock) {
lock.notifyAll();
}
@@ -115,7 +120,9 @@ void setValue(T value) {
void setException(Exception exception) {
this.exception = exception;
this.state = FAILED;
- this.callback.ifPresent(ac -> ac.onComplete(null, Optional.of(exception)));
+ if (hasCallback()) {
+ callback.onError(exception);
+ }
synchronized (lock) {
lock.notifyAll();
}
diff --git a/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/AppTest.java b/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/AppTest.java
index 830e66a2d273..d58a3f6b5c30 100644
--- a/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/AppTest.java
+++ b/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/AppTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,17 +22,24 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.async.method.invocation;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
import org.junit.jupiter.api.Test;
-/**
- * Application test
- */
+/** Application test */
class AppTest {
+
+ /**
+ * Issue: Add at least one assertion to this test case.
+ *
+ * Solution: Inserted assertion to check whether the execution of the main method in {@link
+ * App} throws an exception.
+ */
@Test
- void test() throws Exception {
- App.main(new String[]{});
+ void shouldExecuteApplicationWithoutException() {
+
+ assertDoesNotThrow(() -> App.main(new String[] {}));
}
}
diff --git a/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutorTest.java b/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutorTest.java
index 1e54747faf99..d6540ce77309 100644
--- a/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutorTest.java
+++ b/async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/ThreadAsyncExecutorTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,80 +22,63 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.async.method.invocation;
import static java.time.Duration.ofMillis;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertSame;
-import static org.junit.jupiter.api.Assertions.assertTimeout;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.junit.jupiter.api.Assertions.fail;
-import static org.mockito.Matchers.eq;
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.*;
import static org.mockito.Mockito.timeout;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.verifyNoMoreInteractions;
-import static org.mockito.Mockito.verifyZeroInteractions;
import static org.mockito.Mockito.when;
import static org.mockito.internal.verification.VerificationModeFactory.times;
-import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.mockito.ArgumentCaptor;
import org.mockito.Captor;
-import org.mockito.Matchers;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
-/**
- * Date: 12/6/15 - 10:49 AM
- *
- * @author Jeroen Meulemeester
- */
+/** ThreadAsyncExecutorTest */
class ThreadAsyncExecutorTest {
- @Captor
- private ArgumentCaptor> optionalCaptor;
+ @Captor private ArgumentCaptor exceptionCaptor;
- @Mock
- private Callable task;
+ @Mock private Callable task;
- @Mock
- private AsyncCallback callback;
+ @Mock private AsyncCallback callback;
@BeforeEach
void setUp() {
- MockitoAnnotations.initMocks(this);
+ MockitoAnnotations.openMocks(this);
}
- /**
- * Test used to verify the happy path of {@link ThreadAsyncExecutor#startProcess(Callable)}
- */
+ /** Test used to verify the happy path of {@link ThreadAsyncExecutor#startProcess(Callable)} */
@Test
- void testSuccessfulTaskWithoutCallback() throws Exception {
- assertTimeout(ofMillis(3000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
-
- final var result = new Object();
- when(task.call()).thenReturn(result);
-
- final var asyncResult = executor.startProcess(task);
- assertNotNull(asyncResult);
- asyncResult.await(); // Prevent timing issues, and wait until the result is available
- assertTrue(asyncResult.isCompleted());
-
- // Our task should only execute once ...
- verify(task, times(1)).call();
-
- // ... and the result should be exactly the same object
- assertSame(result, asyncResult.getValue());
- });
+ void testSuccessfulTaskWithoutCallback() {
+ assertTimeout(
+ ofMillis(3000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+
+ final var result = new Object();
+ when(task.call()).thenReturn(result);
+
+ final var asyncResult = executor.startProcess(task);
+ assertNotNull(asyncResult);
+ asyncResult.await(); // Prevent timing issues, and wait until the result is available
+ assertTrue(asyncResult.isCompleted());
+
+ // Our task should only execute once ...
+ verify(task, times(1)).call();
+
+ // ... and the result should be exactly the same object
+ assertSame(result, asyncResult.getValue());
+ });
}
/**
@@ -101,32 +86,31 @@ void testSuccessfulTaskWithoutCallback() throws Exception {
* AsyncCallback)}
*/
@Test
- void testSuccessfulTaskWithCallback() throws Exception {
- assertTimeout(ofMillis(3000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
-
- final var result = new Object();
- when(task.call()).thenReturn(result);
-
- final var asyncResult = executor.startProcess(task, callback);
- assertNotNull(asyncResult);
- asyncResult.await(); // Prevent timing issues, and wait until the result is available
- assertTrue(asyncResult.isCompleted());
-
- // Our task should only execute once ...
- verify(task, times(1)).call();
-
- // ... same for the callback, we expect our object
- verify(callback, times(1)).onComplete(eq(result), optionalCaptor.capture());
-
- final var optionalException = optionalCaptor.getValue();
- assertNotNull(optionalException);
- assertFalse(optionalException.isPresent());
-
- // ... and the result should be exactly the same object
- assertSame(result, asyncResult.getValue());
- });
+ void testSuccessfulTaskWithCallback() {
+ assertTimeout(
+ ofMillis(3000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+
+ final var result = new Object();
+ when(task.call()).thenReturn(result);
+
+ final var asyncResult = executor.startProcess(task, callback);
+ assertNotNull(asyncResult);
+ asyncResult.await(); // Prevent timing issues, and wait until the result is available
+ assertTrue(asyncResult.isCompleted());
+
+ // Our task should only execute once ...
+ verify(task, times(1)).call();
+
+ // ... same for the callback, we expect our object
+ verify(callback, times(1)).onComplete(eq(result));
+ verify(callback, times(0)).onError(exceptionCaptor.capture());
+
+ // ... and the result should be exactly the same object
+ assertSame(result, asyncResult.getValue());
+ });
}
/**
@@ -134,39 +118,44 @@ void testSuccessfulTaskWithCallback() throws Exception {
* task takes a while to execute
*/
@Test
- void testLongRunningTaskWithoutCallback() throws Exception {
- assertTimeout(ofMillis(5000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
-
- final var result = new Object();
- when(task.call()).thenAnswer(i -> {
- Thread.sleep(1500);
- return result;
- });
-
- final var asyncResult = executor.startProcess(task);
- assertNotNull(asyncResult);
- assertFalse(asyncResult.isCompleted());
-
- try {
- asyncResult.getValue();
- fail("Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
- } catch (IllegalStateException e) {
- assertNotNull(e.getMessage());
- }
-
- // Our task should only execute once, but it can take a while ...
- verify(task, timeout(3000).times(1)).call();
-
- // Prevent timing issues, and wait until the result is available
- asyncResult.await();
- assertTrue(asyncResult.isCompleted());
- verifyNoMoreInteractions(task);
-
- // ... and the result should be exactly the same object
- assertSame(result, asyncResult.getValue());
- });
+ void testLongRunningTaskWithoutCallback() {
+ assertTimeout(
+ ofMillis(5000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+
+ final var result = new Object();
+ when(task.call())
+ .thenAnswer(
+ i -> {
+ Thread.sleep(1500);
+ return result;
+ });
+
+ final var asyncResult = executor.startProcess(task);
+ assertNotNull(asyncResult);
+ assertFalse(asyncResult.isCompleted());
+
+ try {
+ asyncResult.getValue();
+ fail(
+ "Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
+ } catch (IllegalStateException e) {
+ assertNotNull(e.getMessage());
+ }
+
+ // Our task should only execute once, but it can take a while ...
+ verify(task, timeout(3000).times(1)).call();
+
+ // Prevent timing issues, and wait until the result is available
+ asyncResult.await();
+ assertTrue(asyncResult.isCompleted());
+ verifyNoMoreInteractions(task);
+
+ // ... and the result should be exactly the same object
+ assertSame(result, asyncResult.getValue());
+ });
}
/**
@@ -174,46 +163,48 @@ void testLongRunningTaskWithoutCallback() throws Exception {
* AsyncCallback)} when a task takes a while to execute
*/
@Test
- void testLongRunningTaskWithCallback() throws Exception {
- assertTimeout(ofMillis(5000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
-
- final var result = new Object();
- when(task.call()).thenAnswer(i -> {
- Thread.sleep(1500);
- return result;
- });
-
- final var asyncResult = executor.startProcess(task, callback);
- assertNotNull(asyncResult);
- assertFalse(asyncResult.isCompleted());
-
- verifyZeroInteractions(callback);
-
- try {
- asyncResult.getValue();
- fail("Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
- } catch (IllegalStateException e) {
- assertNotNull(e.getMessage());
- }
-
- // Our task should only execute once, but it can take a while ...
- verify(task, timeout(3000).times(1)).call();
- verify(callback, timeout(3000).times(1)).onComplete(eq(result), optionalCaptor.capture());
-
- final var optionalException = optionalCaptor.getValue();
- assertNotNull(optionalException);
- assertFalse(optionalException.isPresent());
-
- // Prevent timing issues, and wait until the result is available
- asyncResult.await();
- assertTrue(asyncResult.isCompleted());
- verifyNoMoreInteractions(task, callback);
-
- // ... and the result should be exactly the same object
- assertSame(result, asyncResult.getValue());
- });
+ void testLongRunningTaskWithCallback() {
+ assertTimeout(
+ ofMillis(5000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+
+ final var result = new Object();
+ when(task.call())
+ .thenAnswer(
+ i -> {
+ Thread.sleep(1500);
+ return result;
+ });
+
+ final var asyncResult = executor.startProcess(task, callback);
+ assertNotNull(asyncResult);
+ assertFalse(asyncResult.isCompleted());
+
+ verifyNoMoreInteractions(callback);
+
+ try {
+ asyncResult.getValue();
+ fail(
+ "Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
+ } catch (IllegalStateException e) {
+ assertNotNull(e.getMessage());
+ }
+
+ // Our task should only execute once, but it can take a while ...
+ verify(task, timeout(3000).times(1)).call();
+ verify(callback, timeout(3000).times(1)).onComplete(eq(result));
+ verify(callback, times(0)).onError(isA(Exception.class));
+
+ // Prevent timing issues, and wait until the result is available
+ asyncResult.await();
+ assertTrue(asyncResult.isCompleted());
+ verifyNoMoreInteractions(task, callback);
+
+ // ... and the result should be exactly the same object
+ assertSame(result, asyncResult.getValue());
+ });
}
/**
@@ -222,36 +213,41 @@ void testLongRunningTaskWithCallback() throws Exception {
* ThreadAsyncExecutor#endProcess(AsyncResult)}
*/
@Test
- void testEndProcess() throws Exception {
- assertTimeout(ofMillis(5000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
-
- final var result = new Object();
- when(task.call()).thenAnswer(i -> {
- Thread.sleep(1500);
- return result;
- });
-
- final var asyncResult = executor.startProcess(task);
- assertNotNull(asyncResult);
- assertFalse(asyncResult.isCompleted());
-
- try {
- asyncResult.getValue();
- fail("Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
- } catch (IllegalStateException e) {
- assertNotNull(e.getMessage());
- }
-
- assertSame(result, executor.endProcess(asyncResult));
- verify(task, times(1)).call();
- assertTrue(asyncResult.isCompleted());
-
- // Calling end process a second time while already finished should give the same result
- assertSame(result, executor.endProcess(asyncResult));
- verifyNoMoreInteractions(task);
- });
+ void testEndProcess() {
+ assertTimeout(
+ ofMillis(5000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+
+ final var result = new Object();
+ when(task.call())
+ .thenAnswer(
+ i -> {
+ Thread.sleep(1500);
+ return result;
+ });
+
+ final var asyncResult = executor.startProcess(task);
+ assertNotNull(asyncResult);
+ assertFalse(asyncResult.isCompleted());
+
+ try {
+ asyncResult.getValue();
+ fail(
+ "Expected IllegalStateException when calling AsyncResult#getValue on a non-completed task");
+ } catch (IllegalStateException e) {
+ assertNotNull(e.getMessage());
+ }
+
+ assertSame(result, executor.endProcess(asyncResult));
+ verify(task, times(1)).call();
+ assertTrue(asyncResult.isCompleted());
+
+ // Calling end process a second time while already finished should give the same result
+ assertSame(result, executor.endProcess(asyncResult));
+ verifyNoMoreInteractions(task);
+ });
}
/**
@@ -259,26 +255,29 @@ void testEndProcess() throws Exception {
* the callable is 'null'
*/
@Test
- void testNullTask() throws Exception {
- assertTimeout(ofMillis(3000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
- final var asyncResult = executor.startProcess(null);
-
- assertNotNull(asyncResult, "The AsyncResult should not be 'null', even though the task was 'null'.");
- asyncResult.await(); // Prevent timing issues, and wait until the result is available
- assertTrue(asyncResult.isCompleted());
-
- try {
- asyncResult.getValue();
- fail("Expected ExecutionException with NPE as cause");
- } catch (final ExecutionException e) {
- assertNotNull(e.getMessage());
- assertNotNull(e.getCause());
- assertEquals(NullPointerException.class, e.getCause().getClass());
- }
- });
-
+ void testNullTask() {
+ assertTimeout(
+ ofMillis(3000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+ final var asyncResult = executor.startProcess(null);
+
+ assertNotNull(
+ asyncResult,
+ "The AsyncResult should not be 'null', even though the task was 'null'.");
+ asyncResult.await(); // Prevent timing issues, and wait until the result is available
+ assertTrue(asyncResult.isCompleted());
+
+ try {
+ asyncResult.getValue();
+ fail("Expected ExecutionException with NPE as cause");
+ } catch (final ExecutionException e) {
+ assertNotNull(e.getMessage());
+ assertNotNull(e.getCause());
+ assertEquals(NullPointerException.class, e.getCause().getClass());
+ }
+ });
}
/**
@@ -286,35 +285,36 @@ void testNullTask() throws Exception {
* AsyncCallback)} when the callable is 'null', but the asynchronous callback is provided
*/
@Test
- void testNullTaskWithCallback() throws Exception {
- assertTimeout(ofMillis(3000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
- final var asyncResult = executor.startProcess(null, callback);
-
- assertNotNull(asyncResult, "The AsyncResult should not be 'null', even though the task was 'null'.");
- asyncResult.await(); // Prevent timing issues, and wait until the result is available
- assertTrue(asyncResult.isCompleted());
- verify(callback, times(1)).onComplete(Matchers.isNull(), optionalCaptor.capture());
-
- final var optionalException = optionalCaptor.getValue();
- assertNotNull(optionalException);
- assertTrue(optionalException.isPresent());
-
- final var exception = optionalException.get();
- assertNotNull(exception);
- assertEquals(NullPointerException.class, exception.getClass());
-
- try {
- asyncResult.getValue();
- fail("Expected ExecutionException with NPE as cause");
- } catch (final ExecutionException e) {
- assertNotNull(e.getMessage());
- assertNotNull(e.getCause());
- assertEquals(NullPointerException.class, e.getCause().getClass());
- }
- });
-
+ void testNullTaskWithCallback() {
+ assertTimeout(
+ ofMillis(3000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+ final var asyncResult = executor.startProcess(null, callback);
+
+ assertNotNull(
+ asyncResult,
+ "The AsyncResult should not be 'null', even though the task was 'null'.");
+ asyncResult.await(); // Prevent timing issues, and wait until the result is available
+ assertTrue(asyncResult.isCompleted());
+ verify(callback, times(0)).onComplete(any());
+ verify(callback, times(1)).onError(exceptionCaptor.capture());
+
+ final var exception = exceptionCaptor.getValue();
+ assertNotNull(exception);
+
+ assertEquals(NullPointerException.class, exception.getClass());
+
+ try {
+ asyncResult.getValue();
+ fail("Expected ExecutionException with NPE as cause");
+ } catch (final ExecutionException e) {
+ assertNotNull(e.getMessage());
+ assertNotNull(e.getCause());
+ assertEquals(NullPointerException.class, e.getCause().getClass());
+ }
+ });
}
/**
@@ -322,29 +322,28 @@ void testNullTaskWithCallback() throws Exception {
* AsyncCallback)} when both the callable and the asynchronous callback are 'null'
*/
@Test
- void testNullTaskWithNullCallback() throws Exception {
- assertTimeout(ofMillis(3000), () -> {
- // Instantiate a new executor and start a new 'null' task ...
- final var executor = new ThreadAsyncExecutor();
- final var asyncResult = executor.startProcess(null, null);
-
- assertNotNull(
- asyncResult,
- "The AsyncResult should not be 'null', even though the task and callback were 'null'."
- );
- asyncResult.await(); // Prevent timing issues, and wait until the result is available
- assertTrue(asyncResult.isCompleted());
-
- try {
- asyncResult.getValue();
- fail("Expected ExecutionException with NPE as cause");
- } catch (final ExecutionException e) {
- assertNotNull(e.getMessage());
- assertNotNull(e.getCause());
- assertEquals(NullPointerException.class, e.getCause().getClass());
- }
- });
-
+ void testNullTaskWithNullCallback() {
+ assertTimeout(
+ ofMillis(3000),
+ () -> {
+ // Instantiate a new executor and start a new 'null' task ...
+ final var executor = new ThreadAsyncExecutor();
+ final var asyncResult = executor.startProcess(null, null);
+
+ assertNotNull(
+ asyncResult,
+ "The AsyncResult should not be 'null', even though the task and callback were 'null'.");
+ asyncResult.await(); // Prevent timing issues, and wait until the result is available
+ assertTrue(asyncResult.isCompleted());
+
+ try {
+ asyncResult.getValue();
+ fail("Expected ExecutionException with NPE as cause");
+ } catch (final ExecutionException e) {
+ assertNotNull(e.getMessage());
+ assertNotNull(e.getCause());
+ assertEquals(NullPointerException.class, e.getCause().getClass());
+ }
+ });
}
-
-}
\ No newline at end of file
+}
diff --git a/backends-for-frontends/README.md b/backends-for-frontends/README.md
new file mode 100644
index 000000000000..12038e821e38
--- /dev/null
+++ b/backends-for-frontends/README.md
@@ -0,0 +1,148 @@
+---
+title: "Backends For Frontends Pattern in Java: Tailoring APIs to Client Needs"
+shortTitle: Backends For Frontends
+description: "Learn the Backends For Frontends (BFF) design pattern in Java. Understand how to give each client type its own dedicated backend service, with real-world examples, code, and diagrams."
+category: Architectural
+language: en
+tag:
+ - API design
+ - Architecture
+ - Client-server
+ - Decoupling
+ - Microservices
+---
+
+## Also known as
+
+* Backend For Frontend
+* BFF Pattern
+
+## Intent of Backends For Frontends Pattern
+
+Provide each client-side application (mobile, desktop, chatbot, and so on) with its own dedicated
+backend service, so every client gets an API shaped exactly for its own needs instead of sharing
+one general-purpose backend with every other client.
+
+## Detailed Explanation of Backends For Frontends Pattern with Real-World Examples
+
+Real-world example
+
+> Imagine a retail company whose mobile app, desktop back-office tool, and support chatbot all
+> need customer, cart, order and supplier data -- but a phone screen wants a short summary while
+> the back-office desktop tool wants full order and stock detail. Rather than exposing one shared
+> API that every client has to filter or over-fetch from, the company stands up a small BFF service
+> for the mobile clients and a separate BFF service for the intranet clients. Each BFF calls only
+> the downstream microservices its client needs and returns a payload shaped for that client.
+
+In plain words
+
+> Give every kind of client its own tailor-made backend, instead of forcing all clients through one
+> one-size-fits-all API.
+
+Sam Newman, who popularized the pattern, says
+
+> Create separate backend services to be consumed by specific frontend applications or interfaces.
+
+## Architecture Diagram
+
+```
+node mobile{
+ component iosapp as "ios app"
+ component androidapp as "android app"
+}
+node intranet{
+ component desktop as "desktop app"
+ component chatbot
+}
+component bff as "BFF server"{
+ component iosbff as "ios BFF"
+ component androidbff as "android BFF"
+ component chatbotbff as "chatbot BFF"
+ component desktopbff as "desktop BFF"
+}
+node intranetserv as "intranet services server"{
+ component ss as "supplier service API"
+}
+cloud onlypublic as "public cloud"{
+ component cas as "customer authentication service API"
+ component cs as "cart service API"
+}
+cloud cloudserv as "managed cloud"{
+ component os as "order service API"
+}
+iosapp -- iosbff
+androidapp -- androidbff
+chatbot -- chatbotbff
+desktop -- desktopbff
+iosbff -- cas
+androidbff -- cas
+iosbff -- cs
+androidbff -- cs
+iosbff -- os
+androidbff -- os
+chatbotbff -- os
+desktopbff -- os
+chatbotbff -- ss
+desktopbff -- ss
+```
+
+This example implements a simplified version of the diagram above with two client-facing BFFs
+instead of four, to keep the demo focused: a **Mobile BFF** standing in for the ios/android BFFs,
+and a **Desktop BFF** standing in for the desktop/chatbot BFFs. Both call into the same shared
+downstream services (`AuthService`, `OrderService`), while `CartService` is only used by the
+Mobile BFF and `SupplierService` is only reachable from the Desktop BFF, matching the fan-out
+shown in the diagram.
+
+## Class Diagram
+
+
+
+## When to Use the Backends For Frontends Pattern in Java
+
+* Different client types (mobile, web, desktop, voice/chat) need meaningfully different shapes,
+ granularity, or aggregation of the same underlying data.
+* A single shared API has grown a large number of client-specific conditional branches, optional
+ fields, or query parameters to accommodate every consumer.
+* Different client teams need to iterate on their own API independently without coordinating
+ changes through one shared backend team.
+* Some clients (e.g. mobile) need aggressively trimmed payloads for bandwidth/latency reasons,
+ while others (e.g. an internal desktop tool) need much richer data.
+
+## Benefits and Trade-offs of Backends For Frontends Pattern
+
+Benefits:
+
+* Each client gets an API optimized for its own needs, improving performance and simplicity on
+ the client side.
+* Client teams can evolve their BFF independently, reducing cross-team coordination.
+* Downstream microservices stay generic and reusable; client-specific logic lives in the BFF
+ layer instead of leaking into shared services.
+
+Trade-offs:
+
+* Introduces additional services to build, deploy, and operate.
+* Logic that is genuinely shared across clients can end up duplicated across BFFs if not
+ carefully factored out.
+* Adds an extra network hop between the client and the downstream services.
+
+## How to Implement Backends For Frontends Pattern in Java
+
+1. Identify the distinct client types that need meaningfully different data shapes.
+2. Define the downstream services each client's data actually depends on (`AuthService`,
+ `CartService`, `OrderService`, `SupplierService` in this example).
+3. Create one BFF per client type, implementing a shared `ClientBff` contract, where each BFF
+ only depends on the downstream services its client needs.
+4. Have each BFF aggregate and reshape the downstream data into a response DTO tailored to its
+ client (`MobileDashboardResponse`, `DesktopDashboardResponse`).
+5. Wire the client applications to call their own BFF rather than the downstream services
+ directly.
+
+## Source Code
+
+* [Pattern: Backends For Frontends](https://samnewman.io/patterns/architectural/bff/) by Sam Newman
+* [Microservices Patterns: With examples in Java](https://www.amazon.com/Microservices-Patterns-examples-Chris-Richardson/dp/1617294543) by Chris Richardson
+
+## References and Credits
+
+* [Building Microservices](https://www.oreilly.com/library/view/building-microservices-2nd/9781492034018/) by Sam Newman
+* [Pattern: Backend for frontend (microservices.io)](https://microservices.io/patterns/apigateway.html)
diff --git a/backends-for-frontends/etc/backends-for-frontends.png b/backends-for-frontends/etc/backends-for-frontends.png
new file mode 100644
index 000000000000..f42c786fecf4
Binary files /dev/null and b/backends-for-frontends/etc/backends-for-frontends.png differ
diff --git a/backends-for-frontends/etc/backends-for-frontends.urm.puml b/backends-for-frontends/etc/backends-for-frontends.urm.puml
new file mode 100644
index 000000000000..b09c06742d27
--- /dev/null
+++ b/backends-for-frontends/etc/backends-for-frontends.urm.puml
@@ -0,0 +1,130 @@
+@startuml
+package com.iluwatar.bff {
+ class App {
+ - LOGGER : Logger {static}
+ - USER_ID : String {static}
+ - PRODUCT_ID : String {static}
+ - DEMO_PRICE_USD : double {static}
+ - DEMO_STOCK_LEVEL : int {static}
+ + App()
+ + main(args : String[]) {static}
+ }
+}
+package com.iluwatar.bff.bff {
+ interface ClientBff {
+ + getDashboard(userId : String) : T {abstract}
+ }
+ class DesktopBff {
+ - authService : AuthService
+ - orderService : OrderService
+ - supplierService : SupplierService
+ + DesktopBff(auth : AuthService, orders : OrderService, suppliers : SupplierService)
+ + getDashboard(userId : String) : DesktopDashboardResponse
+ }
+ class MobileBff {
+ - MAX_RECENT_ORDERS : int {static}
+ - authService : AuthService
+ - cartService : CartService
+ - orderService : OrderService
+ + MobileBff(auth : AuthService, cart : CartService, orders : OrderService)
+ + getDashboard(userId : String) : MobileDashboardResponse
+ }
+}
+package com.iluwatar.bff.dto {
+ class DesktopDashboardResponse {
+ - greeting : String
+ - loyaltyTier : String
+ - orderStatuses : List
+ - supplierStockSummaries : List
+ + DesktopDashboardResponse(greeting : String, loyaltyTier : String, orderStatuses : List, supplierStockSummaries : List)
+ }
+ class MobileDashboardResponse {
+ - greeting : String
+ - cartItemCount : int
+ - cartTotalUsd : double
+ - recentOrderSummaries : List
+ + MobileDashboardResponse(greeting : String, cartItemCount : int, cartTotalUsd : double, recentOrderSummaries : List)
+ }
+}
+package com.iluwatar.bff.model {
+ class CartItem {
+ - product : Product
+ - quantity : int
+ + CartItem(product : Product, quantity : int)
+ + lineTotal() : double
+ }
+ class Order {
+ - id : String
+ - productName : String
+ - status : String
+ + Order(id : String, productName : String, status : String)
+ }
+ class Product {
+ - id : String
+ - name : String
+ - priceUsd : double
+ + Product(id : String, name : String, priceUsd : double)
+ }
+ class SupplierRecord {
+ - productId : String
+ - supplierName : String
+ - stockLevel : int
+ + SupplierRecord(productId : String, supplierName : String, stockLevel : int)
+ }
+ class User {
+ - id : String
+ - displayName : String
+ - loyaltyTier : String
+ + User(id : String, displayName : String, loyaltyTier : String)
+ }
+}
+package com.iluwatar.bff.service {
+ interface AuthService {
+ + getUser(userId : String) : User {abstract}
+ }
+ interface CartService {
+ + getCart(userId : String) : List {abstract}
+ }
+ interface OrderService {
+ + getOrders(userId : String) : List {abstract}
+ }
+ interface SupplierService {
+ + getSupplierRecords(productId : String) : List {abstract}
+ }
+}
+package com.iluwatar.bff.service.impl {
+ class InMemoryAuthService {
+ - users : Map
+ + InMemoryAuthService(userData : Map)
+ + getUser(userId : String) : User
+ }
+ class InMemoryCartService {
+ - cartsByUserId : Map>
+ + InMemoryCartService(carts : Map>)
+ + getCart(userId : String) : List
+ }
+ class InMemoryOrderService {
+ - ordersByUserId : Map>
+ + InMemoryOrderService(orders : Map>)
+ + getOrders(userId : String) : List
+ }
+ class InMemorySupplierService {
+ - recordsByProductId : Map>
+ + InMemorySupplierService(records : Map>)
+ + getSupplierRecords(productId : String) : List
+ }
+}
+DesktopBff ..|> ClientBff
+MobileBff ..|> ClientBff
+DesktopBff --> "-authService" AuthService
+DesktopBff --> "-orderService" OrderService
+DesktopBff --> "-supplierService" SupplierService
+MobileBff --> "-authService" AuthService
+MobileBff --> "-cartService" CartService
+MobileBff --> "-orderService" OrderService
+InMemoryAuthService ..|> AuthService
+InMemoryCartService ..|> CartService
+InMemoryOrderService ..|> OrderService
+InMemorySupplierService ..|> SupplierService
+CartItem --> "-product" Product
+@enduml
diff --git a/backends-for-frontends/pom.xml b/backends-for-frontends/pom.xml
new file mode 100644
index 000000000000..8f1e454fa646
--- /dev/null
+++ b/backends-for-frontends/pom.xml
@@ -0,0 +1,67 @@
+
+
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+
+ backends-for-frontends
+
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+ org.slf4j
+ slf4j-api
+
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-jar-plugin
+
+
+
+ com.iluwatar.bff.App
+
+
+
+
+
+
+
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/App.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/App.java
new file mode 100644
index 000000000000..b76939c53fd4
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/App.java
@@ -0,0 +1,109 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff;
+
+import com.iluwatar.bff.bff.DesktopBff;
+import com.iluwatar.bff.bff.MobileBff;
+import com.iluwatar.bff.model.CartItem;
+import com.iluwatar.bff.model.Order;
+import com.iluwatar.bff.model.Product;
+import com.iluwatar.bff.model.SupplierRecord;
+import com.iluwatar.bff.model.User;
+import com.iluwatar.bff.service.impl.InMemoryAuthService;
+import com.iluwatar.bff.service.impl.InMemoryCartService;
+import com.iluwatar.bff.service.impl.InMemoryOrderService;
+import com.iluwatar.bff.service.impl.InMemorySupplierService;
+import java.util.List;
+import java.util.Map;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * {@link App} demonstrates the Backends For Frontends (BFF) pattern.
+ *
+ * A single set of downstream microservices (customer authentication, cart, order and supplier
+ * services) is shared by every client. Two different client-facing gateways -- {@link MobileBff}
+ * for the mobile apps and {@link DesktopBff} for the intranet desktop/chatbot clients -- each call
+ * a different subset of those services and reshape the results into a response tailored to what
+ * their own client actually needs, rather than exposing one one-size-fits-all API to every client.
+ */
+public final class App {
+
+ /** Logger for this class. */
+ private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
+
+ /** User id used in the demonstration. */
+ private static final String USER_ID = "u-1";
+
+ /** Product id used in the demonstration. */
+ private static final String PRODUCT_ID = "p-42";
+
+ /** Unit price of the demo product in US dollars. */
+ private static final double DEMO_PRICE_USD = 79.99;
+
+ /** Supplier stock level used in the demonstration. */
+ private static final int DEMO_STOCK_LEVEL = 120;
+
+ private App() {
+ // utility class
+ }
+
+ /**
+ * Program entry point.
+ *
+ * @param args no argument sent
+ */
+ public static void main(final String[] args) {
+ // shared downstream microservices, as drawn in the pattern diagram
+ var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
+
+ var product = new Product(PRODUCT_ID, "Wireless Headphones", DEMO_PRICE_USD);
+ var cartService = new InMemoryCartService(Map.of(USER_ID, List.of(new CartItem(product, 2))));
+
+ var orderService =
+ new InMemoryOrderService(
+ Map.of(
+ USER_ID,
+ List.of(
+ new Order("o-1", "Wireless Headphones", "DELIVERED"),
+ new Order("o-2", "USB-C Cable", "IN_TRANSIT"))));
+
+ var supplierService =
+ new InMemorySupplierService(
+ Map.of(
+ "Wireless Headphones",
+ List.of(new SupplierRecord(PRODUCT_ID, "Acme Audio Co.", DEMO_STOCK_LEVEL))));
+
+ // client-specific BFFs, each calling only the services their client needs
+ var mobileBff = new MobileBff(authService, cartService, orderService);
+ var desktopBff = new DesktopBff(authService, orderService, supplierService);
+
+ var mobileResponse = mobileBff.getDashboard(USER_ID);
+ LOGGER.info("Mobile BFF response: {}", mobileResponse);
+
+ var desktopResponse = desktopBff.getDashboard(USER_ID);
+ LOGGER.info("Desktop BFF response: {}", desktopResponse);
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/ClientBff.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/ClientBff.java
new file mode 100644
index 000000000000..4c1d8d768ecb
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/ClientBff.java
@@ -0,0 +1,44 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.bff;
+
+/**
+ * Common contract every client-specific Backend For Frontend implements: given a user id, build
+ * whatever response shape ({@code T}) that particular client needs. Each implementation is free to
+ * call a different subset of downstream services and aggregate them differently -- that freedom is
+ * the entire point of the pattern.
+ *
+ * @param the response DTO shape this BFF returns to its client
+ */
+public interface ClientBff {
+
+ /**
+ * Builds the dashboard response for a given user, tailored to this BFF's client.
+ *
+ * @param userId identifier of the user requesting their dashboard
+ * @return the client-specific response
+ */
+ T getDashboard(String userId);
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/DesktopBff.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/DesktopBff.java
new file mode 100644
index 000000000000..1073f4556558
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/DesktopBff.java
@@ -0,0 +1,94 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.bff;
+
+import com.iluwatar.bff.dto.DesktopDashboardResponse;
+import com.iluwatar.bff.service.AuthService;
+import com.iluwatar.bff.service.OrderService;
+import com.iluwatar.bff.service.SupplierService;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Backend For Frontend serving the intranet clients (desktop app, chatbot) from the diagram. It
+ * aggregates the auth, order and supplier services and reshapes the results into a richer,
+ * back-office style payload. Unlike {@link MobileBff}, it does not touch the cart service at all
+ * and it does reach into the intranet-only supplier service, matching the fan-out drawn in the
+ * pattern diagram.
+ */
+public final class DesktopBff implements ClientBff {
+
+ /** The customer authentication service. */
+ private final AuthService authService;
+
+ /** The order service. */
+ private final OrderService orderService;
+
+ /** The supplier service (intranet-only). */
+ private final SupplierService supplierService;
+
+ /**
+ * Creates a desktop BFF wired to the downstream services it depends on.
+ *
+ * @param auth the customer authentication service
+ * @param orders the order service
+ * @param suppliers the supplier service
+ */
+ public DesktopBff(
+ final AuthService auth, final OrderService orders, final SupplierService suppliers) {
+ this.authService = auth;
+ this.orderService = orders;
+ this.supplierService = suppliers;
+ }
+
+ @Override
+ public DesktopDashboardResponse getDashboard(final String userId) {
+ var user = authService.getUser(userId);
+ var orders = orderService.getOrders(userId);
+
+ var orderStatuses =
+ orders.stream()
+ .map(order -> order.id() + ": " + order.productName() + " [" + order.status() + "]")
+ .toList();
+
+ var supplierStockSummaries = new ArrayList();
+ for (var order : orders) {
+ for (var supplierRecord : supplierService.getSupplierRecords(order.productName())) {
+ supplierStockSummaries.add(
+ supplierRecord.supplierName()
+ + ": "
+ + supplierRecord.stockLevel()
+ + " units of "
+ + order.productName());
+ }
+ }
+
+ return new DesktopDashboardResponse(
+ "Welcome back, " + user.displayName(),
+ user.loyaltyTier(),
+ List.copyOf(orderStatuses),
+ List.copyOf(supplierStockSummaries));
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/MobileBff.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/MobileBff.java
new file mode 100644
index 000000000000..a51a7c8a8201
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/MobileBff.java
@@ -0,0 +1,86 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.bff;
+
+import com.iluwatar.bff.dto.MobileDashboardResponse;
+import com.iluwatar.bff.service.AuthService;
+import com.iluwatar.bff.service.CartService;
+import com.iluwatar.bff.service.OrderService;
+import java.util.List;
+
+/**
+ * Backend For Frontend serving the mobile clients (iOS app, Android app) from the diagram. It
+ * aggregates the auth, cart and order services and reshapes the results into a small payload suited
+ * to a phone screen and a limited-bandwidth connection. It never calls the supplier service: a
+ * mobile shopper has no use for back-office stock data, so this BFF simply does not expose it,
+ * rather than sending it and letting the client ignore it.
+ */
+public final class MobileBff implements ClientBff {
+
+ /** Maximum number of recent order summaries to include in the mobile response. */
+ private static final int MAX_RECENT_ORDERS = 3;
+
+ /** The customer authentication service. */
+ private final AuthService authService;
+
+ /** The cart service. */
+ private final CartService cartService;
+
+ /** The order service. */
+ private final OrderService orderService;
+
+ /**
+ * Creates a mobile BFF wired to the downstream services it depends on.
+ *
+ * @param auth the customer authentication service
+ * @param cart the cart service
+ * @param orders the order service
+ */
+ public MobileBff(final AuthService auth, final CartService cart, final OrderService orders) {
+ this.authService = auth;
+ this.cartService = cart;
+ this.orderService = orders;
+ }
+
+ @Override
+ public MobileDashboardResponse getDashboard(final String userId) {
+ var user = authService.getUser(userId);
+ var cart = cartService.getCart(userId);
+ var orders = orderService.getOrders(userId);
+
+ var cartTotal = cart.stream().mapToDouble(item -> item.lineTotal()).sum();
+ var recentOrderSummaries =
+ orders.stream()
+ .limit(MAX_RECENT_ORDERS)
+ .map(order -> order.productName() + " (" + order.status() + ")")
+ .toList();
+
+ return new MobileDashboardResponse(
+ "Hi " + user.displayName() + "!",
+ cart.size(),
+ cartTotal,
+ List.copyOf(recentOrderSummaries));
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/package-info.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/package-info.java
new file mode 100644
index 000000000000..c338c3158023
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/bff/package-info.java
@@ -0,0 +1,29 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+/**
+ * Client-specific Backend For Frontend implementations: one per client type (mobile, desktop) that
+ * each aggregate a different subset of downstream services.
+ */
+package com.iluwatar.bff.bff;
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/DesktopDashboardResponse.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/DesktopDashboardResponse.java
new file mode 100644
index 000000000000..434e1f1cc088
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/DesktopDashboardResponse.java
@@ -0,0 +1,42 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.dto;
+
+import java.util.List;
+
+/**
+ * The shape of data the desktop back-office client renders: richer than the mobile payload,
+ * including full order status and supplier stock levels that a mobile shopper never needs.
+ *
+ * @param greeting a short personalized greeting for the user
+ * @param loyaltyTier the user's loyalty program tier
+ * @param orderStatuses detailed "id: productName [status]" lines for every order
+ * @param supplierStockSummaries "supplierName: stockLevel units" lines for relevant products
+ */
+public record DesktopDashboardResponse(
+ String greeting,
+ String loyaltyTier,
+ List orderStatuses,
+ List supplierStockSummaries) {}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/MobileDashboardResponse.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/MobileDashboardResponse.java
new file mode 100644
index 000000000000..d6d27619c36d
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/MobileDashboardResponse.java
@@ -0,0 +1,39 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.dto;
+
+import java.util.List;
+
+/**
+ * The shape of data the mobile (iOS/Android) client actually renders: a lean payload with just
+ * enough for a small screen, deliberately excluding fields the desktop client needs.
+ *
+ * @param greeting a short personalized greeting for the user
+ * @param cartItemCount number of items currently in the user's cart
+ * @param cartTotalUsd total value of the user's cart in US dollars
+ * @param recentOrderSummaries short human-readable summaries of the user's most recent orders
+ */
+public record MobileDashboardResponse(
+ String greeting, int cartItemCount, double cartTotalUsd, List recentOrderSummaries) {}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/package-info.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/package-info.java
new file mode 100644
index 000000000000..43a23d0dbc4e
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/dto/package-info.java
@@ -0,0 +1,28 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+/**
+ * Response DTOs shaped by each BFF for its specific client (mobile dashboard, desktop dashboard).
+ */
+package com.iluwatar.bff.dto;
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/model/CartItem.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/CartItem.java
new file mode 100644
index 000000000000..a71c4848c791
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/CartItem.java
@@ -0,0 +1,43 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.model;
+
+/**
+ * A single line item inside a user's shopping cart, as returned by the cart service API.
+ *
+ * @param product the product being purchased
+ * @param quantity number of units of the product
+ */
+public record CartItem(Product product, int quantity) {
+
+ /**
+ * Computes the line total for this cart item.
+ *
+ * @return quantity multiplied by unit price
+ */
+ public double lineTotal() {
+ return quantity * product.priceUsd();
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/model/Order.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/Order.java
new file mode 100644
index 000000000000..02a2026695b0
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/Order.java
@@ -0,0 +1,34 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.model;
+
+/**
+ * A past order returned by the order service API.
+ *
+ * @param id order identifier
+ * @param productName name of the ordered product
+ * @param status current fulfillment status, e.g. "DELIVERED", "IN_TRANSIT"
+ */
+public record Order(String id, String productName, String status) {}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/model/Product.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/Product.java
new file mode 100644
index 000000000000..ae4176860b6e
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/Product.java
@@ -0,0 +1,35 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.model;
+
+/**
+ * Simple product record returned by the downstream Cart/Order services. Represents the data a
+ * catalog or cart entry carries before each BFF trims or reshapes it for its own client.
+ *
+ * @param id product identifier
+ * @param name display name of the product
+ * @param priceUsd unit price in US dollars
+ */
+public record Product(String id, String name, double priceUsd) {}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/model/SupplierRecord.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/SupplierRecord.java
new file mode 100644
index 000000000000..f7dfa38fe89d
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/SupplierRecord.java
@@ -0,0 +1,35 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.model;
+
+/**
+ * A supplier stock record returned by the supplier service API, used by the desktop back-office
+ * client to show inventory information that mobile customers never need to see.
+ *
+ * @param productId identifier of the product this record refers to
+ * @param supplierName name of the supplying vendor
+ * @param stockLevel units currently available from this supplier
+ */
+public record SupplierRecord(String productId, String supplierName, int stockLevel) {}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/model/User.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/User.java
new file mode 100644
index 000000000000..5c59c7f963ec
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/User.java
@@ -0,0 +1,35 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.model;
+
+/**
+ * Authenticated user profile returned by the customer authentication service API. Kept
+ * intentionally minimal; each BFF decides which of these fields its client actually needs.
+ *
+ * @param id unique user identifier
+ * @param displayName human-readable name of the user
+ * @param loyaltyTier loyalty program tier, e.g. "GOLD", "SILVER", "STANDARD"
+ */
+public record User(String id, String displayName, String loyaltyTier) {}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/model/package-info.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/package-info.java
new file mode 100644
index 000000000000..37d2855a8671
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/model/package-info.java
@@ -0,0 +1,30 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+/**
+ * Domain model records shared across downstream services: User, Product, CartItem, Order, and
+ * SupplierRecord. Each BFF consumes these raw domain objects and reshapes them into its own
+ * client-specific DTO.
+ */
+package com.iluwatar.bff.model;
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/package-info.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/package-info.java
new file mode 100644
index 000000000000..ede18f2b22f9
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/package-info.java
@@ -0,0 +1,29 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+/**
+ * Backends For Frontends pattern: a dedicated gateway per client type (mobile, desktop) that
+ * aggregates only the downstream services each client actually needs.
+ */
+package com.iluwatar.bff;
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/AuthService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/AuthService.java
new file mode 100644
index 000000000000..a87b75b48bb6
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/AuthService.java
@@ -0,0 +1,43 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service;
+
+import com.iluwatar.bff.model.User;
+
+/**
+ * Represents the customer authentication service API from the diagram: a downstream microservice
+ * shared by every client-specific BFF. Each BFF calls this the same way; only what they do with the
+ * result differs.
+ */
+public interface AuthService {
+
+ /**
+ * Looks up the authenticated user profile for the given id.
+ *
+ * @param userId identifier of the user to look up
+ * @return the matching {@link User}
+ */
+ User getUser(String userId);
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/CartService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/CartService.java
new file mode 100644
index 000000000000..7ae24fba64bc
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/CartService.java
@@ -0,0 +1,43 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service;
+
+import com.iluwatar.bff.model.CartItem;
+import java.util.List;
+
+/**
+ * Represents the cart service API from the diagram. In this example only the mobile and android
+ * clients need cart data, so only {@link com.iluwatar.bff.bff.MobileBff} calls this service.
+ */
+public interface CartService {
+
+ /**
+ * Retrieves the current cart contents for a user.
+ *
+ * @param userId identifier of the user whose cart is requested
+ * @return the list of items currently in the user's cart
+ */
+ List getCart(String userId);
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/OrderService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/OrderService.java
new file mode 100644
index 000000000000..b8e6ee8fa03e
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/OrderService.java
@@ -0,0 +1,43 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service;
+
+import com.iluwatar.bff.model.Order;
+import java.util.List;
+
+/**
+ * Represents the order service API from the diagram. This downstream service is shared by every
+ * client-specific BFF, matching the fan-out shown for "order service API" in the pattern diagram.
+ */
+public interface OrderService {
+
+ /**
+ * Retrieves the order history for a user.
+ *
+ * @param userId identifier of the user whose orders are requested
+ * @return the list of past orders for the user
+ */
+ List getOrders(String userId);
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/SupplierService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/SupplierService.java
new file mode 100644
index 000000000000..ac7c2dfbc849
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/SupplierService.java
@@ -0,0 +1,43 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service;
+
+import com.iluwatar.bff.model.SupplierRecord;
+import java.util.List;
+
+/**
+ * Represents the supplier service API from the diagram, reachable only from the intranet services
+ * server. Only back-office style clients (desktop app, chatbot) call this service.
+ */
+public interface SupplierService {
+
+ /**
+ * Retrieves supplier stock records for a product.
+ *
+ * @param productName name of the product to check stock for
+ * @return the list of supplier stock records for the product
+ */
+ List getSupplierRecords(String productName);
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryAuthService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryAuthService.java
new file mode 100644
index 000000000000..5c2ffc35958f
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryAuthService.java
@@ -0,0 +1,58 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import com.iluwatar.bff.model.User;
+import com.iluwatar.bff.service.AuthService;
+import java.util.Map;
+
+/**
+ * In-memory stand-in for the real customer authentication service API. Real deployments would
+ * replace this with an HTTP/gRPC client; the BFFs are written against the {@link AuthService}
+ * interface, so swapping the implementation later requires no change to any BFF.
+ */
+public final class InMemoryAuthService implements AuthService {
+
+ /** Users stored in memory, keyed by user id. */
+ private final Map users;
+
+ /**
+ * Creates the service with a fixed backing map of users, keyed by user id.
+ *
+ * @param userData the user data this service serves
+ */
+ public InMemoryAuthService(final Map userData) {
+ this.users = userData;
+ }
+
+ @Override
+ public User getUser(final String userId) {
+ var user = users.get(userId);
+ if (user == null) {
+ throw new IllegalArgumentException("Unknown user id: " + userId);
+ }
+ return user;
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryCartService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryCartService.java
new file mode 100644
index 000000000000..fed3b59da2c8
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryCartService.java
@@ -0,0 +1,51 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import com.iluwatar.bff.model.CartItem;
+import com.iluwatar.bff.service.CartService;
+import java.util.List;
+import java.util.Map;
+
+/** In-memory stand-in for the real cart service API. */
+public final class InMemoryCartService implements CartService {
+
+ /** Carts stored in memory, keyed by user id. */
+ private final Map> cartsByUserId;
+
+ /**
+ * Creates the service with a fixed backing map of carts, keyed by user id.
+ *
+ * @param carts the cart data this service serves
+ */
+ public InMemoryCartService(final Map> carts) {
+ this.cartsByUserId = carts;
+ }
+
+ @Override
+ public List getCart(final String userId) {
+ return cartsByUserId.getOrDefault(userId, List.of());
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryOrderService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryOrderService.java
new file mode 100644
index 000000000000..979956d06244
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemoryOrderService.java
@@ -0,0 +1,51 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import com.iluwatar.bff.model.Order;
+import com.iluwatar.bff.service.OrderService;
+import java.util.List;
+import java.util.Map;
+
+/** In-memory stand-in for the real order service API. */
+public final class InMemoryOrderService implements OrderService {
+
+ /** Order histories stored in memory, keyed by user id. */
+ private final Map> ordersByUserId;
+
+ /**
+ * Creates the service with a fixed backing map of order histories, keyed by user id.
+ *
+ * @param orders the order data this service serves
+ */
+ public InMemoryOrderService(final Map> orders) {
+ this.ordersByUserId = orders;
+ }
+
+ @Override
+ public List getOrders(final String userId) {
+ return ordersByUserId.getOrDefault(userId, List.of());
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemorySupplierService.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemorySupplierService.java
new file mode 100644
index 000000000000..ac2d351db3a5
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemorySupplierService.java
@@ -0,0 +1,51 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import com.iluwatar.bff.model.SupplierRecord;
+import com.iluwatar.bff.service.SupplierService;
+import java.util.List;
+import java.util.Map;
+
+/** In-memory stand-in for the real supplier service API, reachable only from the intranet. */
+public final class InMemorySupplierService implements SupplierService {
+
+ /** Supplier records stored in memory, keyed by product name. */
+ private final Map> recordsByProductName;
+
+ /**
+ * Creates the service with a fixed backing map of supplier records, keyed by product name.
+ *
+ * @param records the supplier data this service serves
+ */
+ public InMemorySupplierService(final Map> records) {
+ this.recordsByProductName = records;
+ }
+
+ @Override
+ public List getSupplierRecords(final String productName) {
+ return recordsByProductName.getOrDefault(productName, List.of());
+ }
+}
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/package-info.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/package-info.java
new file mode 100644
index 000000000000..fbdb5d026bc8
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/package-info.java
@@ -0,0 +1,29 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+/**
+ * In-memory implementations of the downstream service API interfaces, used for the pattern
+ * demonstration. Production deployments would replace these with real HTTP/gRPC clients.
+ */
+package com.iluwatar.bff.service.impl;
diff --git a/backends-for-frontends/src/main/java/com/iluwatar/bff/service/package-info.java b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/package-info.java
new file mode 100644
index 000000000000..05bfcb3911df
--- /dev/null
+++ b/backends-for-frontends/src/main/java/com/iluwatar/bff/service/package-info.java
@@ -0,0 +1,29 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+/**
+ * Downstream service API interfaces shared by all BFFs: AuthService, CartService, OrderService, and
+ * SupplierService. Each BFF wires in only the services its client requires.
+ */
+package com.iluwatar.bff.service;
diff --git a/backends-for-frontends/src/test/java/com/iluwatar/bff/AppTest.java b/backends-for-frontends/src/test/java/com/iluwatar/bff/AppTest.java
new file mode 100644
index 000000000000..d06d945c8c33
--- /dev/null
+++ b/backends-for-frontends/src/test/java/com/iluwatar/bff/AppTest.java
@@ -0,0 +1,41 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests that {@link App}'s demo entry point runs end-to-end without throwing, following the
+ * convention used throughout this repository for pattern demo apps.
+ */
+class AppTest {
+
+ @Test
+ void mainShouldRunWithoutException() {
+ assertDoesNotThrow(() -> App.main(new String[] {}));
+ }
+}
diff --git a/backends-for-frontends/src/test/java/com/iluwatar/bff/bff/DesktopBffTest.java b/backends-for-frontends/src/test/java/com/iluwatar/bff/bff/DesktopBffTest.java
new file mode 100644
index 000000000000..d4a2331b101b
--- /dev/null
+++ b/backends-for-frontends/src/test/java/com/iluwatar/bff/bff/DesktopBffTest.java
@@ -0,0 +1,77 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.bff;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.iluwatar.bff.model.Order;
+import com.iluwatar.bff.model.SupplierRecord;
+import com.iluwatar.bff.model.User;
+import com.iluwatar.bff.service.impl.InMemoryAuthService;
+import com.iluwatar.bff.service.impl.InMemoryOrderService;
+import com.iluwatar.bff.service.impl.InMemorySupplierService;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Tests for {@link DesktopBff}. */
+class DesktopBffTest {
+
+ private static final String USER_ID = "u-1";
+
+ @Test
+ void shouldAggregateOrdersAndSupplierStockIntoDesktopShape() {
+ var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
+ var orderService =
+ new InMemoryOrderService(
+ Map.of(USER_ID, List.of(new Order("o-1", "Headphones", "DELIVERED"))));
+ var supplierService =
+ new InMemorySupplierService(
+ Map.of("Headphones", List.of(new SupplierRecord("p-1", "Acme Audio", 30))));
+
+ var bff = new DesktopBff(authService, orderService, supplierService);
+ var response = bff.getDashboard(USER_ID);
+
+ assertEquals("Welcome back, Alice", response.greeting());
+ assertEquals("GOLD", response.loyaltyTier());
+ assertTrue(response.orderStatuses().get(0).contains("Headphones"));
+ assertTrue(response.supplierStockSummaries().get(0).contains("Acme Audio"));
+ }
+
+ @Test
+ void shouldReturnNoSupplierSummariesWhenNoOrdersExist() {
+ var authService =
+ new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Carol", "STANDARD")));
+ var orderService = new InMemoryOrderService(Map.of(USER_ID, List.of()));
+ var supplierService = new InMemorySupplierService(Map.of());
+
+ var bff = new DesktopBff(authService, orderService, supplierService);
+ var response = bff.getDashboard(USER_ID);
+
+ assertEquals(0, response.orderStatuses().size());
+ assertEquals(0, response.supplierStockSummaries().size());
+ }
+}
diff --git a/backends-for-frontends/src/test/java/com/iluwatar/bff/bff/MobileBffTest.java b/backends-for-frontends/src/test/java/com/iluwatar/bff/bff/MobileBffTest.java
new file mode 100644
index 000000000000..f05a0be99b61
--- /dev/null
+++ b/backends-for-frontends/src/test/java/com/iluwatar/bff/bff/MobileBffTest.java
@@ -0,0 +1,83 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.bff;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.iluwatar.bff.model.CartItem;
+import com.iluwatar.bff.model.Order;
+import com.iluwatar.bff.model.Product;
+import com.iluwatar.bff.model.User;
+import com.iluwatar.bff.service.impl.InMemoryAuthService;
+import com.iluwatar.bff.service.impl.InMemoryCartService;
+import com.iluwatar.bff.service.impl.InMemoryOrderService;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Tests for {@link MobileBff}. */
+class MobileBffTest {
+
+ private static final String USER_ID = "u-1";
+
+ @Test
+ void shouldAggregateCartAndOrdersIntoMobileShape() {
+ var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
+ var product = new Product("p-1", "Headphones", 50.0);
+ var cartService = new InMemoryCartService(Map.of(USER_ID, List.of(new CartItem(product, 2))));
+ var orderService =
+ new InMemoryOrderService(
+ Map.of(USER_ID, List.of(new Order("o-1", "Headphones", "DELIVERED"))));
+
+ var bff = new MobileBff(authService, cartService, orderService);
+ var response = bff.getDashboard(USER_ID);
+
+ assertEquals("Hi Alice!", response.greeting());
+ assertEquals(1, response.cartItemCount());
+ assertEquals(100.0, response.cartTotalUsd());
+ assertTrue(response.recentOrderSummaries().get(0).contains("Headphones"));
+ }
+
+ @Test
+ void shouldCapRecentOrderSummariesAtThree() {
+ var authService = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Bob", "SILVER")));
+ var cartService = new InMemoryCartService(Map.of(USER_ID, List.of()));
+ var orderService =
+ new InMemoryOrderService(
+ Map.of(
+ USER_ID,
+ List.of(
+ new Order("o-1", "A", "DELIVERED"),
+ new Order("o-2", "B", "DELIVERED"),
+ new Order("o-3", "C", "DELIVERED"),
+ new Order("o-4", "D", "DELIVERED"))));
+
+ var bff = new MobileBff(authService, cartService, orderService);
+ var response = bff.getDashboard(USER_ID);
+
+ assertEquals(3, response.recentOrderSummaries().size());
+ }
+}
diff --git a/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryAuthServiceTest.java b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryAuthServiceTest.java
new file mode 100644
index 000000000000..db4da0c0ba0d
--- /dev/null
+++ b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryAuthServiceTest.java
@@ -0,0 +1,54 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import com.iluwatar.bff.model.User;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Tests for {@link InMemoryAuthService}. */
+class InMemoryAuthServiceTest {
+
+ private static final String USER_ID = "u-1";
+
+ @Test
+ void shouldReturnUserForKnownId() {
+ var expected = new User(USER_ID, "Alice", "GOLD");
+ var service = new InMemoryAuthService(Map.of(USER_ID, expected));
+
+ var actual = service.getUser(USER_ID);
+
+ assertEquals(expected, actual);
+ }
+
+ @Test
+ void shouldThrowForUnknownId() {
+ var service = new InMemoryAuthService(Map.of(USER_ID, new User(USER_ID, "Alice", "GOLD")));
+
+ assertThrows(IllegalArgumentException.class, () -> service.getUser("unknown-id"));
+ }
+}
diff --git a/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryCartServiceTest.java b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryCartServiceTest.java
new file mode 100644
index 000000000000..19e54841fa44
--- /dev/null
+++ b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryCartServiceTest.java
@@ -0,0 +1,60 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.iluwatar.bff.model.CartItem;
+import com.iluwatar.bff.model.Product;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Tests for {@link InMemoryCartService}. */
+class InMemoryCartServiceTest {
+
+ private static final String USER_ID = "u-1";
+
+ @Test
+ void shouldReturnCartItemsForKnownUser() {
+ var product = new Product("p-1", "Headphones", 49.99);
+ var item = new CartItem(product, 2);
+ var service = new InMemoryCartService(Map.of(USER_ID, List.of(item)));
+
+ var cart = service.getCart(USER_ID);
+
+ assertEquals(1, cart.size());
+ assertEquals(item, cart.get(0));
+ }
+
+ @Test
+ void shouldReturnEmptyListForUnknownUser() {
+ var service = new InMemoryCartService(Map.of());
+
+ var cart = service.getCart("unknown-user");
+
+ assertTrue(cart.isEmpty());
+ }
+}
diff --git a/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryOrderServiceTest.java b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryOrderServiceTest.java
new file mode 100644
index 000000000000..26b7d82be105
--- /dev/null
+++ b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemoryOrderServiceTest.java
@@ -0,0 +1,58 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.iluwatar.bff.model.Order;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Tests for {@link InMemoryOrderService}. */
+class InMemoryOrderServiceTest {
+
+ private static final String USER_ID = "u-1";
+
+ @Test
+ void shouldReturnOrdersForKnownUser() {
+ var order = new Order("o-1", "Headphones", "DELIVERED");
+ var service = new InMemoryOrderService(Map.of(USER_ID, List.of(order)));
+
+ var orders = service.getOrders(USER_ID);
+
+ assertEquals(1, orders.size());
+ assertEquals(order, orders.get(0));
+ }
+
+ @Test
+ void shouldReturnEmptyListForUnknownUser() {
+ var service = new InMemoryOrderService(Map.of());
+
+ var orders = service.getOrders("unknown-user");
+
+ assertTrue(orders.isEmpty());
+ }
+}
diff --git a/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemorySupplierServiceTest.java b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemorySupplierServiceTest.java
new file mode 100644
index 000000000000..ce5d39041033
--- /dev/null
+++ b/backends-for-frontends/src/test/java/com/iluwatar/bff/service/impl/InMemorySupplierServiceTest.java
@@ -0,0 +1,58 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bff.service.impl;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.iluwatar.bff.model.SupplierRecord;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/** Tests for {@link InMemorySupplierService}. */
+class InMemorySupplierServiceTest {
+
+ private static final String PRODUCT_NAME = "Headphones";
+
+ @Test
+ void shouldReturnSupplierRecordsForKnownProductName() {
+ var record = new SupplierRecord("p-1", "Acme Audio", 30);
+ var service = new InMemorySupplierService(Map.of(PRODUCT_NAME, List.of(record)));
+
+ var records = service.getSupplierRecords(PRODUCT_NAME);
+
+ assertEquals(1, records.size());
+ assertEquals(record, records.get(0));
+ }
+
+ @Test
+ void shouldReturnEmptyListForUnknownProductName() {
+ var service = new InMemorySupplierService(Map.of());
+
+ var records = service.getSupplierRecords("unknown-product");
+
+ assertTrue(records.isEmpty());
+ }
+}
diff --git a/backpressure/README.md b/backpressure/README.md
new file mode 100644
index 000000000000..d0734ad1f934
--- /dev/null
+++ b/backpressure/README.md
@@ -0,0 +1,156 @@
+---
+title: "Backpressure Pattern in Java: Gracefully regulate producer-to-consumer data flow to prevent overload."
+shortTitle: Backpressure
+description: "Dive into the Backpressure design pattern in Java through practical examples, discovering how it prevents overload while ensuring stability and peak performance by aligning data flow with consumer capacity."
+category: Concurrency
+language: en
+tag:
+ - Asynchronous
+ - Event-driven
+ - Reactive
+ - Resilience
+---
+
+## Also known as
+
+* Flow Control
+* Rate Limiting Mechanism
+
+## Intent of the Backpressure Design Pattern
+
+Control the rate of data production so downstream consumers are not overwhelmed by excessive load.
+
+## Detailed Explanation of Backpressure Pattern with Real-World Examples
+
+Real-world example
+
+> Imagine a busy coffee shop where multiple baristas brew drinks (producers), and a single barista is responsible for carefully crafting latte art (consumer). If drinks are brewed faster than the latte-art barista can decorate them, they pile up, risking quality issues or discarded drinks. By introducing a pacing system—only sending new cups once the latte-art barista is ready—everyone stays synchronized, ensuring minimal waste and a consistently enjoyable customer experience.
+
+In plain words
+
+> The Backpressure design pattern is a flow control mechanism that prevents overwhelming a system by regulating data production based on the consumer’s processing capacity.
+
+Wikipedia says
+
+> Back pressure (or backpressure) is the term for a resistance to the desired flow of fluid through pipes. Obstructions or tight bends create backpressure via friction loss and pressure drop. In distributed systems in particular event-driven architecture, back pressure is a technique to regulate flow of data, ensuring that components do not become overwhelmed.
+
+Sequence diagram
+
+
+
+## Programmatic Example of Backpressure Pattern in Java
+
+This example demonstrates how backpressure can be implemented using Project Reactor. We begin by creating a simple publisher that emits a stream of integers, introducing a small delay to mimic a slower production rate:
+
+```java
+public class Publisher {
+ public static Flux publish(int start, int count, int delay) {
+ return Flux.range(start, count).delayElements(Duration.ofMillis(delay)).log();
+ }
+}
+```
+
+Next, we define a custom subscriber by extending Reactor’s BaseSubscriber. It simulates slow processing by sleeping for 500ms per item. Initially, the subscriber requests ten items; for every five items processed, it requests five more:
+
+```java
+public class Subscriber extends BaseSubscriber {
+
+ private static final Logger logger = LoggerFactory.getLogger(Subscriber.class);
+
+ @Override
+ protected void hookOnSubscribe(@NonNull Subscription subscription) {
+ logger.info("subscribe()");
+ request(10); //request 10 items initially
+ }
+
+ @Override
+ protected void hookOnNext(@NonNull Integer value) {
+ processItem();
+ logger.info("process({})", value);
+ if (value % 5 == 0) {
+ // request for the next 5 items after processing first 5
+ request(5);
+ }
+ }
+
+ @Override
+ protected void hookOnComplete() {
+ //completed processing.
+ }
+
+ private void processItem() {
+ try {
+ Thread.sleep(500); // simulate slow processing
+ } catch (InterruptedException e) {
+ logger.error(e.getMessage(), e);
+ }
+ }
+}
+```
+
+Finally, in the `main` method, we publish a range of integers and subscribe using the custom subscriber. A short sleep in the main thread allows the emission, backpressure requests, and processing to be fully observed:
+
+```java
+public static void main(String[] args) throws InterruptedException {
+ Subscriber sub = new Subscriber();
+ Publisher.publish(1, 8, 200).subscribe(sub);
+ Thread.sleep(5000); //wait for execution
+
+}
+```
+
+Below is an example of the program’s output. It shows the subscriber’s log entries, including when it requests more data and when each integer is processed:
+
+```
+23:09:55.746 [main] DEBUG reactor.util.Loggers -- Using Slf4j logging framework
+23:09:55.762 [main] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onSubscribe(FluxConcatMapNoPrefetch.FluxConcatMapNoPrefetchSubscriber)
+23:09:55.762 [main] INFO com.iluwatar.backpressure.Subscriber -- subscribe()
+23:09:55.763 [main] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- request(10)
+23:09:55.969 [parallel-1] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(1)
+23:09:56.475 [parallel-1] INFO com.iluwatar.backpressure.Subscriber -- process(1)
+23:09:56.680 [parallel-2] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(2)
+23:09:57.185 [parallel-2] INFO com.iluwatar.backpressure.Subscriber -- process(2)
+23:09:57.389 [parallel-3] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(3)
+23:09:57.894 [parallel-3] INFO com.iluwatar.backpressure.Subscriber -- process(3)
+23:09:58.099 [parallel-4] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(4)
+23:09:58.599 [parallel-4] INFO com.iluwatar.backpressure.Subscriber -- process(4)
+23:09:58.805 [parallel-5] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(5)
+23:09:59.311 [parallel-5] INFO com.iluwatar.backpressure.Subscriber -- process(5)
+23:09:59.311 [parallel-5] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- request(5)
+23:09:59.516 [parallel-6] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(6)
+23:10:00.018 [parallel-6] INFO com.iluwatar.backpressure.Subscriber -- process(6)
+23:10:00.223 [parallel-7] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(7)
+23:10:00.729 [parallel-7] INFO com.iluwatar.backpressure.Subscriber -- process(7)
+23:10:00.930 [parallel-8] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onNext(8)
+23:10:01.436 [parallel-8] INFO com.iluwatar.backpressure.Subscriber -- process(8)
+23:10:01.437 [parallel-8] INFO reactor.Flux.ConcatMapNoPrefetch.1 -- onComplete()
+```
+
+## When to Use the Backpressure Pattern In Java
+
+* Use in Java systems where data is produced at high velocity and consumers risk overload.
+* Applicable in reactive or event-driven architectures to maintain stability under varying load conditions.
+
+## Benefits and Trade-offs of Backpressure Pattern
+
+Benefits:
+
+* Protects consumers from saturation and resource exhaustion.
+
+Trade-offs:
+
+* Introduces possible delays if production must slow down to match consumer capacity.
+* Requires careful orchestration in complex systems with multiple concurrent data sources.
+
+## Related Java Design Patterns
+
+* [Observer Pattern](https://java-design-patterns.com/patterns/observer/): Both patterns involve a producer notifying consumers. Observer is synchronous and tightly coupled (observers know the subject).
+* [Publish-Subscribe Pattern](https://java-design-patterns.com/patterns/publish-subscribe/): Both patterns deal with asynchronous data flow and can work together to manage message distribution and consumption effectively.
+
+## References and Credits
+
+* [Backpressure Explained (RedHat Developers Blog)](https://developers.redhat.com/articles/backpressure-explained)
+* [Hands-On Reactive Programming in Spring 5](https://amzn.to/3YuYfyO)
+* [Reactive Programming with RxJava: Creating Asynchronous, Event-Based Applications](https://amzn.to/42negbf)
+* [Reactive Streams in Java](https://amzn.to/3RJjUzA)
+* [Reactive Streams Specification](https://www.reactive-streams.org/)
diff --git a/backpressure/etc/backpressure-sequence-diagram.png b/backpressure/etc/backpressure-sequence-diagram.png
new file mode 100644
index 000000000000..b74a5d2a5362
Binary files /dev/null and b/backpressure/etc/backpressure-sequence-diagram.png differ
diff --git a/backpressure/etc/backpressure.png b/backpressure/etc/backpressure.png
new file mode 100644
index 000000000000..0de9ff54b673
Binary files /dev/null and b/backpressure/etc/backpressure.png differ
diff --git a/backpressure/pom.xml b/backpressure/pom.xml
new file mode 100644
index 000000000000..8f6a54178799
--- /dev/null
+++ b/backpressure/pom.xml
@@ -0,0 +1,81 @@
+
+
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+
+ backpressure
+
+
+
+ io.projectreactor
+ reactor-core
+ 3.8.0-M1
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+ io.projectreactor
+ reactor-test
+ 3.8.0-RC1
+ test
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.backpressure.App
+
+
+
+
+
+
+
+
+
\ No newline at end of file
diff --git a/backpressure/src/main/java/com/iluwatar/backpressure/App.java b/backpressure/src/main/java/com/iluwatar/backpressure/App.java
new file mode 100644
index 000000000000..4632c42a467f
--- /dev/null
+++ b/backpressure/src/main/java/com/iluwatar/backpressure/App.java
@@ -0,0 +1,76 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.backpressure;
+
+import java.util.concurrent.CountDownLatch;
+
+/**
+ * The Backpressure pattern is a flow control mechanism. It allows a consumer to signal to a
+ * producer to slow down or stop sending data when it's overwhelmed.
+ * Prevents memory overflow, CPU thrashing, and resource exhaustion.
+ * Ensures fair usage of resources in distributed systems.
+ * Avoids buffer bloat and latency spikes. Key concepts of this design paradigm involves
+ * Publisher/Producer: Generates data.
+ * Subscriber/Consumer: Receives and processes data.
+ *
+ * In this example we will create a {@link Publisher} and a {@link Subscriber}. Publisher
+ * will emit a stream of integer values with a predefined delay. Subscriber takes 500 ms to
+ * process one integer. Since the subscriber can't process the items fast enough we apply
+ * backpressure to the publisher so that it will request 10 items first, process 5 items and
+ * request for the next 5 again. After processing 5 items subscriber will keep requesting for
+ * another 5 until the stream ends.
+ */
+public class App {
+
+ protected static CountDownLatch latch;
+
+ /**
+ * Program entry point.
+ *
+ * @param args command line args
+ */
+ public static void main(String[] args) throws InterruptedException {
+
+ /*
+ * This custom subscriber applies backpressure:
+ * - Has a processing delay of 0.5 milliseconds
+ * - Requests 10 items initially
+ * - Process 5 items and request for the next 5 items
+ */
+ Subscriber sub = new Subscriber();
+ // slow publisher emit 15 numbers with a delay of 200 milliseconds
+ Publisher.publish(1, 17, 200).subscribe(sub);
+
+ latch = new CountDownLatch(1);
+ latch.await();
+
+ sub = new Subscriber();
+ // fast publisher emit 15 numbers with a delay of 1 millisecond
+ Publisher.publish(1, 17, 1).subscribe(sub);
+
+ latch = new CountDownLatch(1);
+ latch.await();
+ }
+}
diff --git a/backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java b/backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java
new file mode 100644
index 000000000000..1d39a070ae57
--- /dev/null
+++ b/backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java
@@ -0,0 +1,46 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.backpressure;
+
+import java.time.Duration;
+import reactor.core.publisher.Flux;
+
+/** This class is the publisher that generates the data stream. */
+public class Publisher {
+
+ private Publisher() {}
+
+ /**
+ * On message method will trigger when the subscribed event is published.
+ *
+ * @param start starting integer
+ * @param count how many integers to emit
+ * @param delay delay between each item in milliseconds
+ * @return a flux stream of integers
+ */
+ public static Flux publish(int start, int count, int delay) {
+ return Flux.range(start, count).delayElements(Duration.ofMillis(delay)).log();
+ }
+}
diff --git a/backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java b/backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java
new file mode 100644
index 000000000000..40ff5aebc814
--- /dev/null
+++ b/backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java
@@ -0,0 +1,64 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.backpressure;
+
+import lombok.NonNull;
+import lombok.extern.slf4j.Slf4j;
+import org.reactivestreams.Subscription;
+import reactor.core.publisher.BaseSubscriber;
+
+/** This class is the custom subscriber that subscribes to the data stream. */
+@Slf4j
+public class Subscriber extends BaseSubscriber {
+
+ @Override
+ protected void hookOnSubscribe(@NonNull Subscription subscription) {
+ request(10); // request 10 items initially
+ }
+
+ @Override
+ protected void hookOnNext(@NonNull Integer value) {
+ processItem();
+ LOGGER.info("process({})", value);
+ if (value % 5 == 0) {
+ // request for the next 5 items after processing first 5
+ request(5);
+ }
+ }
+
+ @Override
+ protected void hookOnComplete() {
+ App.latch.countDown();
+ }
+
+ private void processItem() {
+ try {
+ Thread.sleep(500); // simulate slow processing
+ } catch (InterruptedException e) {
+ LOGGER.error(e.getMessage(), e);
+ Thread.currentThread().interrupt();
+ }
+ }
+}
diff --git a/backpressure/src/test/java/com/iluwatar/backpressure/AppTest.java b/backpressure/src/test/java/com/iluwatar/backpressure/AppTest.java
new file mode 100644
index 000000000000..8fe2245a97b7
--- /dev/null
+++ b/backpressure/src/test/java/com/iluwatar/backpressure/AppTest.java
@@ -0,0 +1,37 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.backpressure;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+import org.junit.jupiter.api.Test;
+
+public class AppTest {
+
+ @Test
+ void shouldExecuteApplicationWithoutException() {
+ assertDoesNotThrow(() -> App.main(new String[] {}));
+ }
+}
diff --git a/backpressure/src/test/java/com/iluwatar/backpressure/LoggerExtension.java b/backpressure/src/test/java/com/iluwatar/backpressure/LoggerExtension.java
new file mode 100644
index 000000000000..e99926e00a1a
--- /dev/null
+++ b/backpressure/src/test/java/com/iluwatar/backpressure/LoggerExtension.java
@@ -0,0 +1,60 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.backpressure;
+
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
+import java.util.List;
+import java.util.stream.Collectors;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.BeforeEachCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.slf4j.LoggerFactory;
+
+public class LoggerExtension implements BeforeEachCallback, AfterEachCallback {
+
+ private final ListAppender listAppender = new ListAppender<>();
+ private final Logger logger = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
+
+ @Override
+ public void afterEach(ExtensionContext extensionContext) {
+ listAppender.stop();
+ listAppender.list.clear();
+ logger.detachAppender(listAppender);
+ }
+
+ @Override
+ public void beforeEach(ExtensionContext extensionContext) {
+ logger.addAppender(listAppender);
+ listAppender.start();
+ }
+
+ public List getFormattedMessages() {
+ return listAppender.list.stream()
+ .map(ILoggingEvent::getFormattedMessage)
+ .collect(Collectors.toList());
+ }
+}
diff --git a/backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java b/backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java
new file mode 100644
index 000000000000..010a80e83959
--- /dev/null
+++ b/backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java
@@ -0,0 +1,51 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.backpressure;
+
+import static com.iluwatar.backpressure.Publisher.publish;
+
+import java.time.Duration;
+import org.junit.jupiter.api.Test;
+import reactor.core.publisher.Flux;
+import reactor.test.StepVerifier;
+
+public class PublisherTest {
+
+ @Test
+ public void testPublish() {
+
+ Flux flux = publish(1, 3, 200);
+
+ StepVerifier.withVirtualTime(() -> flux)
+ .expectSubscription()
+ .expectNoEvent(Duration.ofMillis(200))
+ .expectNext(1)
+ .expectNoEvent(Duration.ofSeconds(200))
+ .expectNext(2)
+ .expectNoEvent(Duration.ofSeconds(200))
+ .expectNext(3)
+ .verifyComplete();
+ }
+}
diff --git a/backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java b/backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java
new file mode 100644
index 000000000000..7f7676612d02
--- /dev/null
+++ b/backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java
@@ -0,0 +1,54 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.backpressure;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.concurrent.CountDownLatch;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+public class SubscriberTest {
+
+ @RegisterExtension public LoggerExtension loggerExtension = new LoggerExtension();
+
+ @Test
+ public void testSubscribe() throws InterruptedException {
+
+ Subscriber sub = new Subscriber();
+ Publisher.publish(1, 8, 100).subscribe(sub);
+
+ App.latch = new CountDownLatch(1);
+ App.latch.await();
+
+ String result = String.join(",", loggerExtension.getFormattedMessages());
+ assertTrue(
+ result.endsWith(
+ "onSubscribe(FluxConcatMapNoPrefetch."
+ + "FluxConcatMapNoPrefetchSubscriber),request(10),onNext(1),process(1),onNext(2),"
+ + "process(2),onNext(3),process(3),onNext(4),process(4),onNext(5),process(5),request(5),"
+ + "onNext(6),process(6),onNext(7),process(7),onNext(8),process(8),onComplete()"));
+ }
+}
diff --git a/balking/README.md b/balking/README.md
index 22257ac7bb52..cdd09cf5b7d1 100644
--- a/balking/README.md
+++ b/balking/README.md
@@ -1,27 +1,161 @@
---
-layout: pattern
-title: Balking
-folder: balking
-permalink: /patterns/balking/
-categories: Concurrency
-tags:
- - Decoupling
+title: "Balking Pattern in Java: Smart Control Over Java Execution"
+shortTitle: Balking
+description: "Learn the Balking design pattern in Java, a concurrency pattern that prevents code execution in inappropriate states. Discover examples, use cases, and benefits."
+category: Concurrency
+language: en
+tag:
+ - Concurrency
+ - Decoupling
+ - Fault tolerance
+ - Synchronization
---
-## Intent
-Balking Pattern is used to prevent an object from executing certain code if it is an
-incomplete or inappropriate state
+## Intent of Balking Design Pattern
-## Class diagram
-
+The Balking Pattern in Java is a concurrency design pattern that prevents an object from executing certain code if it is in an incomplete or inappropriate state. This pattern is crucial for managing state and concurrency in multithreaded Java applications.
+
+## Detailed Explanation of Balking Pattern with Real-World Examples
+
+Real-world example
+
+> A real-world analogy of the Balking design pattern can be seen in a laundry service. Imagine a washing machine at a laundromat that only starts washing clothes if the door is properly closed and locked. If a user tries to start the machine while the door is open, the machine balks and does nothing. This ensures that the washing process only begins when it is safe to do so, preventing water spillage and potential damage to the machine. Similarly, the Balking pattern in software design ensures that operations are only executed when the object is in an appropriate state, preventing erroneous actions and maintaining system stability.
+
+In plain words
+
+> Using the balking pattern, a certain code executes only if the object is in particular state.
+
+Wikipedia says
+
+> The balking pattern is a software design pattern that only executes an action on an object when the object is in a particular state. For example, if an object reads ZIP files and a calling method invokes a get method on the object when the ZIP file is not open, the object would "balk" at the request.
+
+Flowchart
+
+
+
+## Programmatic Example of Balking Pattern in Java
+
+This example demonstrates the Balking Pattern in a multithreaded Java application, highlighting state management and concurrency control. The Balking Pattern is exemplified by a washing machine's start button that initiates washing only if the machine is idle. This ensures state management and prevents concurrent issues.
+
+There's a start-button in a washing machine to initiate the laundry washing. When the washing machine is inactive the button works as expected, but if it's already washing the button does nothing.
+
+In this example implementation, `WashingMachine` is an object that has two states in which it can be: ENABLED and WASHING. If the machine is ENABLED, the state changes to WASHING using a thread-safe method. On the other hand, if it already has been washing and any other thread executes `wash`it won't do that and returns without doing anything.
+
+Here are the relevant parts of the `WashingMachine` class.
+
+```java
+
+@Slf4j
+public class WashingMachine {
+
+ private final DelayProvider delayProvider;
+ private WashingMachineState washingMachineState;
+
+ public WashingMachine(DelayProvider delayProvider) {
+ this.delayProvider = delayProvider;
+ this.washingMachineState = WashingMachineState.ENABLED;
+ }
+
+ public WashingMachineState getWashingMachineState() {
+ return washingMachineState;
+ }
+
+ public void wash() {
+ synchronized (this) {
+ var machineState = getWashingMachineState();
+ LOGGER.info("{}: Actual machine state: {}", Thread.currentThread().getName(), machineState);
+ if (this.washingMachineState == WashingMachineState.WASHING) {
+ LOGGER.error("Cannot wash if the machine has been already washing!");
+ return;
+ }
+ this.washingMachineState = WashingMachineState.WASHING;
+ }
+ LOGGER.info("{}: Doing the washing", Thread.currentThread().getName());
+ this.delayProvider.executeAfterDelay(50, TimeUnit.MILLISECONDS, this::endOfWashing);
+ }
+
+ public synchronized void endOfWashing() {
+ washingMachineState = WashingMachineState.ENABLED;
+ LOGGER.info("{}: Washing completed.", Thread.currentThread().getId());
+ }
+}
+```
+
+Here's the simple `DelayProvider` interface used by the `WashingMachine`.
+
+```java
+public interface DelayProvider {
+ void executeAfterDelay(long interval, TimeUnit timeUnit, Runnable task);
+}
+```
+
+Now, we introduce the application using the `WashingMachine`.
+
+```java
+public static void main(String... args) {
+ final var washingMachine = new WashingMachine();
+ var executorService = Executors.newFixedThreadPool(3);
+ for (int i = 0; i < 3; i++) {
+ executorService.execute(washingMachine::wash);
+ }
+ executorService.shutdown();
+ try {
+ if (!executorService.awaitTermination(10, TimeUnit.SECONDS)) {
+ executorService.shutdownNow();
+ }
+ } catch (InterruptedException ie) {
+ LOGGER.error("ERROR: Waiting on executor service shutdown!");
+ Thread.currentThread().interrupt();
+ }
+}
+```
+
+Here is the console output of the program.
+
+```
+14:02:52.268 [pool-1-thread-2] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-2: Actual machine state: ENABLED
+14:02:52.272 [pool-1-thread-2] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-2: Doing the washing
+14:02:52.272 [pool-1-thread-3] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-3: Actual machine state: WASHING
+14:02:52.273 [pool-1-thread-3] ERROR com.iluwatar.balking.WashingMachine - Cannot wash if the machine has been already washing!
+14:02:52.273 [pool-1-thread-1] INFO com.iluwatar.balking.WashingMachine - pool-1-thread-1: Actual machine state: WASHING
+14:02:52.273 [pool-1-thread-1] ERROR com.iluwatar.balking.WashingMachine - Cannot wash if the machine has been already washing!
+14:02:52.324 [pool-1-thread-2] INFO com.iluwatar.balking.WashingMachine - 14: Washing completed.
+```
+
+## When to Use the Balking Pattern in Java
-## Applicability
Use the Balking pattern when
-* you want to invoke an action on an object only when it is in a particular state
-* objects are generally only in a state that is prone to balking temporarily
-but for an unknown amount of time
+* You want to invoke an action on an object only when it is in a particular state
+* Objects are generally only in a state that is prone to balking temporarily but for an unknown amount of time
+* In multithreaded applications where certain actions should only proceed when specific conditions are met, and those conditions are expected to change over time due to external factors or concurrent operations.
+
+## Real-World Applications of Balking Pattern in Java
+
+* Resource pooling, where resources are only allocated if they are in a valid state for allocation.
+* Thread management, where threads only proceed with tasks if certain conditions (like task availability or resource locks) are met.
+
+## Benefits and Trade-offs of Balking Pattern
+
+Benefits:
+
+* Reduces unnecessary lock acquisitions in situations where actions cannot proceed, enhancing performance in concurrent applications.
+* Encourages clear separation of state management and behavior, leading to cleaner code.
+* Simplifies the handling of operations that should only be performed under certain conditions without cluttering the caller code with state checks.
+
+Trade-offs:
+
+* Can introduce complexity by obscuring the conditions under which actions are taken or ignored, potentially making the system harder to debug and understand.
+* May lead to missed opportunities or actions if the state changes are not properly monitored or if the balking condition is too restrictive.
+
+## Related Java Design Patterns
+
+* [Double-Checked Locking](https://java-design-patterns.com/patterns/double-checked-locking/): Ensures that initialization occurs only when necessary and avoids unnecessary locking, which is related to Balking in terms of conditionally executing logic based on the object's state.
+* [Guarded Suspension](https://java-design-patterns.com/patterns/guarded-suspension/): Similar in ensuring actions are only performed when an object is in a certain state, but typically involves waiting until the state is valid.
+* [State](https://java-design-patterns.com/patterns/state/): The State pattern can be used in conjunction with Balking to manage the states and transitions of the object.
+
+## References and Credits
-## Related patterns
-* Guarded Suspension Pattern
-* Double Checked Locking Pattern
+* [Concurrent Programming in Java : Design Principles and Patterns](https://amzn.to/4dIBqxL)
+* [Java Concurrency in Practice](https://amzn.to/4aRMruW)
+* [Patterns in Java: A Catalog of Reusable Design Patterns Illustrated with UML](https://amzn.to/4bOtzwF)
diff --git a/balking/etc/balking-flowchart.png b/balking/etc/balking-flowchart.png
new file mode 100644
index 000000000000..400a1ce8d3e3
Binary files /dev/null and b/balking/etc/balking-flowchart.png differ
diff --git a/balking/pom.xml b/balking/pom.xml
index 96453169265b..818f7549c330 100644
--- a/balking/pom.xml
+++ b/balking/pom.xml
@@ -1,54 +1,70 @@
-
-
-
- java-design-patterns
- com.iluwatar
- 1.23.0-SNAPSHOT
-
- 4.0.0
+
+
+
+ java-design-patterns
+ com.iluwatar
+ 1.26.0-SNAPSHOT
+
+ 4.0.0
+ balking
+
+
+ org.slf4j
+ slf4j-api
+
+
+ ch.qos.logback
+ logback-classic
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.balking.App
+
+
+
+
+
+
+
+
diff --git a/balking/src/main/java/com/iluwatar/balking/App.java b/balking/src/main/java/com/iluwatar/balking/App.java
index 3e72acc59efc..c7651ec54147 100644
--- a/balking/src/main/java/com/iluwatar/balking/App.java
+++ b/balking/src/main/java/com/iluwatar/balking/App.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,31 +22,26 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.balking;
-import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
/**
* In Balking Design Pattern if an object’s method is invoked when it is in an inappropriate state,
* then the method will return without doing anything. Objects that use this pattern are generally
* only in a state that is prone to balking temporarily but for an unknown amount of time
*
- * In this example implementation WashingMachine is an object that has two states in which it
- * can be: ENABLED and WASHING. If the machine is ENABLED the state is changed into WASHING that any
- * other thread can't invoke this action on this and then do the job. On the other hand if it have
- * been already washing and any other thread execute wash() it can't do that once again and returns
- * doing nothing.
+ *
In this example implementation, {@link WashingMachine} is an object that has two states in
+ * which it can be: ENABLED and WASHING. If the machine is ENABLED, the state changes to WASHING
+ * using a thread-safe method. On the other hand, if it already has been washing and any other
+ * thread executes {@link WashingMachine#wash()} it won't do that and returns without doing
+ * anything.
*/
-
+@Slf4j
public class App {
- private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
-
/**
* Entry Point.
*
@@ -58,10 +55,12 @@ public static void main(String... args) {
}
executorService.shutdown();
try {
- executorService.awaitTermination(10, TimeUnit.SECONDS);
+ if (!executorService.awaitTermination(10, TimeUnit.SECONDS)) {
+ executorService.shutdownNow();
+ }
} catch (InterruptedException ie) {
LOGGER.error("ERROR: Waiting on executor service shutdown!");
+ Thread.currentThread().interrupt();
}
}
-
}
diff --git a/balking/src/main/java/com/iluwatar/balking/DelayProvider.java b/balking/src/main/java/com/iluwatar/balking/DelayProvider.java
index ed05cd292f6f..f27922219ea6 100644
--- a/balking/src/main/java/com/iluwatar/balking/DelayProvider.java
+++ b/balking/src/main/java/com/iluwatar/balking/DelayProvider.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,14 +22,11 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.balking;
import java.util.concurrent.TimeUnit;
-/**
- * An interface to simulate delay while executing some work.
- */
+/** An interface to simulate delay while executing some work. */
public interface DelayProvider {
void executeAfterDelay(long interval, TimeUnit timeUnit, Runnable task);
}
diff --git a/balking/src/main/java/com/iluwatar/balking/WashingMachine.java b/balking/src/main/java/com/iluwatar/balking/WashingMachine.java
index b35bd99dfe61..52ce7c593b6b 100644
--- a/balking/src/main/java/com/iluwatar/balking/WashingMachine.java
+++ b/balking/src/main/java/com/iluwatar/balking/WashingMachine.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,34 +22,32 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.balking;
import java.util.concurrent.TimeUnit;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
-/**
- * Washing machine class.
- */
+/** Washing machine class. */
+@Slf4j
public class WashingMachine {
- private static final Logger LOGGER = LoggerFactory.getLogger(WashingMachine.class);
private final DelayProvider delayProvider;
- private WashingMachineState washingMachineState;
- /**
- * Creates a new instance of WashingMachine.
- */
+ @Getter private WashingMachineState washingMachineState;
+
+ /** Creates a new instance of WashingMachine. */
public WashingMachine() {
- this((interval, timeUnit, task) -> {
- try {
- Thread.sleep(timeUnit.toMillis(interval));
- } catch (InterruptedException ie) {
- ie.printStackTrace();
- }
- task.run();
- });
+ this(
+ (interval, timeUnit, task) -> {
+ try {
+ Thread.sleep(timeUnit.toMillis(interval));
+ } catch (InterruptedException ie) {
+ LOGGER.error("", ie);
+ Thread.currentThread().interrupt();
+ }
+ task.run();
+ });
}
/**
@@ -59,19 +59,13 @@ public WashingMachine(DelayProvider delayProvider) {
this.washingMachineState = WashingMachineState.ENABLED;
}
- public WashingMachineState getWashingMachineState() {
- return washingMachineState;
- }
-
- /**
- * Method responsible for washing if the object is in appropriate state.
- */
+ /** Method responsible for washing if the object is in appropriate state. */
public void wash() {
synchronized (this) {
var machineState = getWashingMachineState();
LOGGER.info("{}: Actual machine state: {}", Thread.currentThread().getName(), machineState);
if (this.washingMachineState == WashingMachineState.WASHING) {
- LOGGER.error("ERROR: Cannot wash if the machine has been already washing!");
+ LOGGER.error("Cannot wash if the machine has been already washing!");
return;
}
this.washingMachineState = WashingMachineState.WASHING;
@@ -81,12 +75,9 @@ public void wash() {
this.delayProvider.executeAfterDelay(50, TimeUnit.MILLISECONDS, this::endOfWashing);
}
- /**
- * Method responsible of ending the washing by changing machine state.
- */
+ /** Method is responsible for ending the washing by changing machine state. */
public synchronized void endOfWashing() {
washingMachineState = WashingMachineState.ENABLED;
LOGGER.info("{}: Washing completed.", Thread.currentThread().getId());
}
-
}
diff --git a/balking/src/main/java/com/iluwatar/balking/WashingMachineState.java b/balking/src/main/java/com/iluwatar/balking/WashingMachineState.java
index 664a4c0c9941..e0b2ba7ac8f1 100644
--- a/balking/src/main/java/com/iluwatar/balking/WashingMachineState.java
+++ b/balking/src/main/java/com/iluwatar/balking/WashingMachineState.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.balking;
/**
@@ -28,5 +29,6 @@
* as well as during washing.
*/
public enum WashingMachineState {
- ENABLED, WASHING
+ ENABLED,
+ WASHING
}
diff --git a/balking/src/test/java/com/iluwatar/balking/AppTest.java b/balking/src/test/java/com/iluwatar/balking/AppTest.java
index 8c75a1f62f69..40beabf553d0 100644
--- a/balking/src/test/java/com/iluwatar/balking/AppTest.java
+++ b/balking/src/test/java/com/iluwatar/balking/AppTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +22,24 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.balking;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.Executable;
-/**
- * Application test
- */
+/** Application test */
class AppTest {
+ /**
+ * Issue: Add at least one assertion to this test case.
+ *
+ *
Solution: Inserted assertion to check whether the execution of the main method in {@link
+ * App} throws an exception.
+ */
@Test
- void main() {
- App.main();
+ void shouldExecuteApplicationWithoutException() {
+ assertDoesNotThrow((Executable) App::main);
}
-
-}
\ No newline at end of file
+}
diff --git a/balking/src/test/java/com/iluwatar/balking/WashingMachineTest.java b/balking/src/test/java/com/iluwatar/balking/WashingMachineTest.java
index 9e218e3f0b76..9bf7ac2548a0 100644
--- a/balking/src/test/java/com/iluwatar/balking/WashingMachineTest.java
+++ b/balking/src/test/java/com/iluwatar/balking/WashingMachineTest.java
@@ -1,6 +1,8 @@
/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
* The MIT License
- * Copyright © 2014-2019 Ilkka Seppälä
+ * Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +22,6 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
-
package com.iluwatar.balking;
import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -28,9 +29,7 @@
import java.util.concurrent.TimeUnit;
import org.junit.jupiter.api.Test;
-/**
- * Tests for {@link WashingMachine}
- */
+/** Tests for {@link WashingMachine} */
class WashingMachineTest {
private final FakeDelayProvider fakeDelayProvider = new FakeDelayProvider();
@@ -68,4 +67,4 @@ public void executeAfterDelay(long interval, TimeUnit timeUnit, Runnable task) {
this.task = task;
}
}
-}
\ No newline at end of file
+}
diff --git a/bloc/README.md b/bloc/README.md
new file mode 100644
index 000000000000..76a4a0917485
--- /dev/null
+++ b/bloc/README.md
@@ -0,0 +1,230 @@
+---
+title: "Bloc Pattern in Java: State Management Simplified"
+shortTitle: Bloc
+description: "Learn how the Bloc pattern helps manage state changes in Java applications. This guide covers dynamic listener management, real-world examples, and clean code practices for state management."
+category: Architectural
+language: en
+tag:
+ - Abstraction
+ - Data binding
+ - Decoupling
+ - Event-driven
+ - Presentation
+ - Reactive
+ - Reusability
+ - State tracking
+---
+
+## Also known as
+
+* Business Logic Component
+* Business Logic Controller
+
+## Intent of the Bloc Pattern
+
+The Bloc pattern manages the state of an object and allows for dynamically notifying interested listeners about state changes. It separates state management logic from the rest of the application, improving code organization and flexibility.
+
+## Detailed explanation of the Bloc pattern with real-World examples
+
+Real-world example
+
+> Consider a digital counter application where multiple parts of the UI need to be updated whenever the counter changes. For example, a label displaying the counter value and an activity log showing changes. Instead of directly modifying these UI components, the Bloc pattern manages the counter state and notifies all registered listeners about the state change. Listeners can dynamically subscribe or unsubscribe from receiving updates.
+
+In plain words
+
+> The Bloc pattern manages a single state object and dynamically notifies registered listeners whenever the state changes.
+
+Wikipedia says
+
+> While not a formalized "Gang of Four" design pattern, Bloc is widely used in state-driven applications. It centralizes state management and propagates state changes to registered observers, following principles of separation of concerns.
+
+Sequence diagram
+
+
+
+## Programmatic Example of the Bloc Pattern in Java
+
+This example demonstrates how to implement the Bloc pattern using Java and Swing. The pattern separates the state of the application from UI components, and provides a reactive, event-driven approach to managing updates.
+
+Core components of the Bloc Pattern include a `State` object, a `Bloc` class responsible for managing and updating that state, and interfaces (`StateListener` and `ListenerManager`) for subscribing to changes.
+
+The `State` class represents the application's data at any given time.
+
+```java
+public record State(int value) {}
+```
+
+The `ListenerManager` interface declares methods to add and remove listeners, as well as retrieve them.
+
+```java
+public interface ListenerManager {
+ void addListener(StateListener listener);
+ void removeListener(StateListener listener);
+ List> getListeners();
+}
+```
+
+The `StateListener` interface defines how a listener reacts to state changes.
+
+```java
+public interface StateListener {
+ void onStateChange(T state);
+}
+```
+
+The `Bloc` class maintains the current state and notifies listeners of updates. It provides `increment` and `decrement` methods to update state and automatically notify registered listeners.
+
+```java
+public class Bloc implements ListenerManager {
+
+ private State currentState;
+ private final List> listeners = new ArrayList<>();
+
+ public Bloc() {
+ this.currentState = new State(0);
+ }
+
+ @Override
+ public void addListener(StateListener listener) {
+ listeners.add(listener);
+ listener.onStateChange(currentState);
+ }
+
+ @Override
+ public void removeListener(StateListener listener) {
+ listeners.remove(listener);
+ }
+
+ @Override
+ public List> getListeners() {
+ return Collections.unmodifiableList(listeners);
+ }
+
+ private void emitState(State newState) {
+ currentState = newState;
+ for (StateListener listener : listeners) {
+ listener.onStateChange(currentState);
+ }
+ }
+
+ public void increment() {
+ emitState(new State(currentState.value() + 1));
+ }
+
+ public void decrement() {
+ emitState(new State(currentState.value() - 1));
+ }
+}
+```
+
+This class demonstrates how to integrate the Bloc pattern with a simple Swing GUI. It sets up a counter, buttons to change the state, and a toggle to enable or disable the listener dynamically.
+
+```java
+public class Main {
+ public static void main(String[] args) {
+ BlocUi blocUi = new BlocUi();
+ blocUi.createAndShowUi();
+ }
+}
+
+public class BlocUi {
+
+ public void createAndShowUi() {
+ final Bloc bloc = new Bloc();
+
+ JFrame frame = new JFrame("BloC example");
+ frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
+ frame.setSize(400, 300);
+
+ JLabel counterLabel = new JLabel("Counter: 0", SwingConstants.CENTER);
+ counterLabel.setFont(new Font("Arial", Font.BOLD, 20));
+
+ JButton decrementButton = new JButton("Decrement");
+ JButton toggleListenerButton = new JButton("Disable Listener");
+ JButton incrementButton = new JButton("Increment");
+
+ frame.setLayout(new BorderLayout());
+ frame.add(counterLabel, BorderLayout.CENTER);
+ frame.add(incrementButton, BorderLayout.NORTH);
+ frame.add(decrementButton, BorderLayout.SOUTH);
+ frame.add(toggleListenerButton, BorderLayout.EAST);
+
+ StateListener stateListener = state -> counterLabel.setText("Counter: " + state.value());
+
+ bloc.addListener(stateListener);
+
+ toggleListenerButton.addActionListener(
+ e -> {
+ if (bloc.getListeners().contains(stateListener)) {
+ bloc.removeListener(stateListener);
+ toggleListenerButton.setText("Enable Listener");
+ } else {
+ bloc.addListener(stateListener);
+ toggleListenerButton.setText("Disable Listener");
+ }
+ });
+
+ incrementButton.addActionListener(e -> bloc.increment());
+ decrementButton.addActionListener(e -> bloc.decrement());
+
+ frame.setVisible(true);
+ }
+}
+```
+
+### Program Output
+
+- **On Increment**
+ `Counter: 1`
+
+- **On Decrement**
+ `Counter: 0`
+
+- **Dynamic Listener Toggle**
+ - Listener disabled: Counter stops updating.
+ - Listener enabled: Counter updates again.
+
+## When to Use the Bloc Pattern
+
+Use the Bloc pattern when:
+
+* When you want a clean separation of business logic and UI in Java applications
+* When you need a reactive approach to updating UI based on state changes
+* When you want to avoid coupling controllers or presenters directly to data manipulation
+* When multiple UI elements need access to the same business logic
+
+## Real-World Applications of Bloc Pattern
+
+* Java-based desktop applications that require real-time UI updates
+* Backend-driven Java frameworks that separate service layers from presentation
+* Cross-platform applications where the logic must remain consistent regardless of the UI technology
+
+## Benefits and Trade-offs of Bloc Pattern
+
+Benefits:
+
+* Simplifies UI components by removing direct business logic
+* Improves testability by isolating state and behavior
+* Encourages code reuse by centralizing data flows
+* Enhances maintainability through clear separation of concerns
+
+Trade-offs:
+
+* May introduce additional boilerplate code for managing streams or observers
+* Requires careful design to avoid a monolithic “god” component
+* Demands consistent reactive programming practices to be effective
+
+## Related Patterns
+
+- [Observer](https://java-design-patterns.com/patterns/observer/): Bloc is a specialized implementation of the Observer pattern.
+- [Mediator](https://java-design-patterns.com/patterns/mediator/): Orchestrates interactions among multiple objects through a central component
+- [MVC](https://java-design-patterns.com/patterns/model-view-controller/): Shares the idea of separating concerns between layers
+
+## References and Credits
+
+* [Bloc architecture(bloclibrary.dev)](https://bloclibrary.dev/architecture/)
+* [Clean Architecture: A Craftsman's Guide to Software Structure and Design](https://amzn.to/3UoKkaR)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
+* [Effective Java](https://amzn.to/4cGk2Jz)
+* [Event-Driven Programming in Java (Oracle)](https://www.oracle.com/java/)
+* [Java Swing Documentation (Oracle)](https://docs.oracle.com/javase/tutorial/uiswing/)
diff --git a/bloc/etc/bloc-sequence-diagram.png b/bloc/etc/bloc-sequence-diagram.png
new file mode 100644
index 000000000000..588863985019
Binary files /dev/null and b/bloc/etc/bloc-sequence-diagram.png differ
diff --git a/bloc/etc/bloc.png b/bloc/etc/bloc.png
new file mode 100644
index 000000000000..60d6eb77c8fc
Binary files /dev/null and b/bloc/etc/bloc.png differ
diff --git a/bloc/etc/bloc.puml b/bloc/etc/bloc.puml
new file mode 100644
index 000000000000..5991f533ae70
--- /dev/null
+++ b/bloc/etc/bloc.puml
@@ -0,0 +1,41 @@
+@startuml
+package com.iluwatar.bloc {
+
+ class State {
+ - value : int
+ + State(value : int)
+ + getValue() : int
+ }
+
+ interface StateListener {
+ + onStateChange(state : T)
+ }
+
+ interface ListenerManager {
+ + addListener(listener : StateListener)
+ + removeListener(listener : StateListener)
+ + getListeners() : List>
+ }
+
+ class BloC {
+ - currentState : State
+ - listeners : List>
+ + BloC()
+ + addListener(listener : StateListener)
+ + removeListener(listener : StateListener)
+ + getListeners() : List>
+ - emitState(newState : State)
+ + increment()
+ + decrement()
+ }
+
+ class Main {
+ + main(args : String[])
+ }
+
+ ListenerManager <|.. BloC
+ StateListener <|.. BloC
+ BloC o-- State
+ BloC *-- StateListener
+}
+@enduml
diff --git a/bloc/etc/bloc.urm.puml b/bloc/etc/bloc.urm.puml
new file mode 100644
index 000000000000..6408aa76e6a4
--- /dev/null
+++ b/bloc/etc/bloc.urm.puml
@@ -0,0 +1,32 @@
+@startuml
+package com.iluwatar.bloc {
+ class Bloc {
+ - currentState : State
+ - listeners : List>
+ + Bloc()
+ + addListener(listener : StateListener)
+ + decrement()
+ - emitState(newState : State)
+ + getListeners() : List>
+ + increment()
+ + removeListener(listener : StateListener)
+ }
+ class BlocUi {
+ + BlocUi()
+ + createAndShowUi()
+ }
+ interface ListenerManager {
+ + addListener(StateListener) {abstract}
+ + getListeners() : List> {abstract}
+ + removeListener(StateListener) {abstract}
+ }
+ class Main {
+ + Main()
+ + main(args : String[]) {static}
+ }
+ interface StateListener {
+ + onStateChange(T) {abstract}
+ }
+}
+Bloc ..|> ListenerManager
+@enduml
\ No newline at end of file
diff --git a/bloc/pom.xml b/bloc/pom.xml
new file mode 100644
index 000000000000..021fbaafeb8d
--- /dev/null
+++ b/bloc/pom.xml
@@ -0,0 +1,76 @@
+
+
+
+ 4.0.0
+
+ com.iluwatar
+ java-design-patterns
+ 1.26.0-SNAPSHOT
+
+ bloc
+
+
+ org.junit.jupiter
+ junit-jupiter-engine
+ test
+
+
+ org.testng
+ testng
+ 7.11.0
+ test
+
+
+ org.assertj
+ assertj-core
+ 3.27.7
+ test
+
+
+
+
+
+ org.apache.maven.plugins
+ maven-assembly-plugin
+
+
+
+
+
+ com.iluwatar.bloc.Main
+
+
+
+
+
+
+
+
+
diff --git a/bloc/src/main/java/com/iluwatar/bloc/Bloc.java b/bloc/src/main/java/com/iluwatar/bloc/Bloc.java
new file mode 100644
index 000000000000..f6ab0a61cdbf
--- /dev/null
+++ b/bloc/src/main/java/com/iluwatar/bloc/Bloc.java
@@ -0,0 +1,98 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * The Bloc class is responsible for managing the current state and notifying registered listeners
+ * whenever the state changes. It implements the ListenerManager interface, allowing listeners to be
+ * added, removed, and notified of state changes.
+ */
+public class Bloc implements ListenerManager {
+
+ private State currentState;
+ private final List> listeners = new ArrayList<>();
+
+ /** Constructs a new Bloc instance with an initial state of value 0. */
+ public Bloc() {
+ this.currentState = new State(0);
+ }
+
+ /**
+ * Adds a listener to receive state change notifications.
+ *
+ * @param listener the listener to add
+ */
+ @Override
+ public void addListener(StateListener listener) {
+ listeners.add(listener);
+ listener.onStateChange(currentState);
+ }
+
+ /**
+ * Removes a listener from receiving state change notifications.
+ *
+ * @param listener the listener to remove
+ */
+ @Override
+ public void removeListener(StateListener listener) {
+ listeners.remove(listener);
+ }
+
+ /**
+ * Returns an unmodifiable list of all registered listeners.
+ *
+ * @return an unmodifiable list of listeners
+ */
+ @Override
+ public List> getListeners() {
+ return Collections.unmodifiableList(listeners);
+ }
+
+ /**
+ * Emits a new state and notifies all registered listeners of the change.
+ *
+ * @param newState the new state to emit
+ */
+ private void emitState(State newState) {
+ currentState = newState;
+ for (StateListener listener : listeners) {
+ listener.onStateChange(currentState);
+ }
+ }
+
+ /** Increments the current state value by 1 and notifies listeners of the change. */
+ public void increment() {
+ emitState(new State(currentState.value() + 1));
+ }
+
+ /** Decrements the current state value by 1 and notifies listeners of the change. */
+ public void decrement() {
+ emitState(new State(currentState.value() - 1));
+ }
+}
diff --git a/bloc/src/main/java/com/iluwatar/bloc/BlocUi.java b/bloc/src/main/java/com/iluwatar/bloc/BlocUi.java
new file mode 100644
index 000000000000..500d455d82e1
--- /dev/null
+++ b/bloc/src/main/java/com/iluwatar/bloc/BlocUi.java
@@ -0,0 +1,85 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+import java.awt.BorderLayout;
+import java.awt.Font;
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.SwingConstants;
+import javax.swing.WindowConstants;
+
+/** The BlocUI class handles the creation and management of the UI components. */
+public class BlocUi {
+
+ /** Creates and shows the UI. */
+ public void createAndShowUi() {
+ // Create a Bloc instance to manage the state
+ final Bloc bloc = new Bloc();
+
+ // setting up a frame window with a title
+ JFrame frame = new JFrame("BloC example");
+ frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
+ frame.setSize(400, 300);
+
+ // label to display the counter value
+ JLabel counterLabel = new JLabel("Counter: 0", SwingConstants.CENTER);
+ counterLabel.setFont(new Font("Arial", Font.BOLD, 20));
+
+ // buttons for increment, decrement, and toggling listener
+ JButton decrementButton = new JButton("Decrement");
+ JButton toggleListenerButton = new JButton("Disable Listener");
+ JButton incrementButton = new JButton("Increment");
+
+ frame.setLayout(new BorderLayout());
+ frame.add(counterLabel, BorderLayout.CENTER);
+ frame.add(incrementButton, BorderLayout.NORTH);
+ frame.add(decrementButton, BorderLayout.SOUTH);
+ frame.add(toggleListenerButton, BorderLayout.EAST);
+
+ // making a state listener to update the counter label when the state changes
+ StateListener stateListener = state -> counterLabel.setText("Counter: " + state.value());
+
+ // adding the listener to the Bloc instance
+ bloc.addListener(stateListener);
+
+ toggleListenerButton.addActionListener(
+ e -> {
+ if (bloc.getListeners().contains(stateListener)) {
+ bloc.removeListener(stateListener);
+ toggleListenerButton.setText("Enable Listener");
+ } else {
+ bloc.addListener(stateListener);
+ toggleListenerButton.setText("Disable Listener");
+ }
+ });
+
+ incrementButton.addActionListener(e -> bloc.increment());
+ decrementButton.addActionListener(e -> bloc.decrement());
+
+ frame.setVisible(true);
+ }
+}
diff --git a/bloc/src/main/java/com/iluwatar/bloc/ListenerManager.java b/bloc/src/main/java/com/iluwatar/bloc/ListenerManager.java
new file mode 100644
index 000000000000..cd55b0fb320d
--- /dev/null
+++ b/bloc/src/main/java/com/iluwatar/bloc/ListenerManager.java
@@ -0,0 +1,56 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+import java.util.List;
+
+/**
+ * Interface for managing listeners for state changes.
+ *
+ * @param The type of state to be handled by the listeners.
+ */
+public interface ListenerManager {
+
+ /**
+ * Adds a listener that will be notified of state changes.
+ *
+ * @param listener the listener to be added
+ */
+ void addListener(StateListener listener);
+
+ /**
+ * Removes a listener so that it no longer receives state change notifications.
+ *
+ * @param listener the listener to be removed
+ */
+ void removeListener(StateListener listener);
+
+ /**
+ * Returns a list of all listeners currently registered for state changes.
+ *
+ * @return a list of registered listeners
+ */
+ List> getListeners();
+}
diff --git a/bloc/src/main/java/com/iluwatar/bloc/Main.java b/bloc/src/main/java/com/iluwatar/bloc/Main.java
new file mode 100644
index 000000000000..b7a929bcf2bd
--- /dev/null
+++ b/bloc/src/main/java/com/iluwatar/bloc/Main.java
@@ -0,0 +1,51 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+/**
+ * The BLoC (Business Logic Component) pattern is a software design pattern primarily used in
+ * Flutter applications. It facilitates the separation of business logic from UI code, making the
+ * application more modular, testable, and scalable. The BLoC pattern uses streams to manage the
+ * flow of data and state changes, allowing widgets to react to new states as they arrive. In the
+ * BLoC pattern, the application is divided into three key components: - Input streams: Represent
+ * user interactions or external events fed into the BLoC. - Business logic: Processes the input and
+ * determines the resulting state or actions. - Output streams: Emit the updated state for the UI to
+ * consume. The BLoC pattern is especially useful in reactive programming scenarios and aligns well
+ * with the declarative nature of Flutter. By using this pattern, developers can ensure a clear
+ * separation of concerns, enhance reusability, and maintain consistent state management throughout
+ * the application.
+ */
+public class Main {
+
+ /**
+ * The entry point of the application. Initializes the GUI.
+ *
+ * @param args command-line arguments (not used in this example)
+ */
+ public static void main(String[] args) {
+ BlocUi blocUi = new BlocUi();
+ blocUi.createAndShowUi();
+ }
+}
diff --git a/bloc/src/main/java/com/iluwatar/bloc/State.java b/bloc/src/main/java/com/iluwatar/bloc/State.java
new file mode 100644
index 000000000000..430747548cd3
--- /dev/null
+++ b/bloc/src/main/java/com/iluwatar/bloc/State.java
@@ -0,0 +1,31 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+/**
+ * The {@code State} class represents a state with an integer value. This class encapsulates the
+ * value and provides methods to retrieve it.
+ */
+public record State(int value) {}
diff --git a/bloc/src/main/java/com/iluwatar/bloc/StateListener.java b/bloc/src/main/java/com/iluwatar/bloc/StateListener.java
new file mode 100644
index 000000000000..77aac172e4e3
--- /dev/null
+++ b/bloc/src/main/java/com/iluwatar/bloc/StateListener.java
@@ -0,0 +1,42 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+/**
+ * The {@code StateListener} interface defines the contract for listening to state changes.
+ * Implementations of this interface should handle state changes and define actions to take when the
+ * state changes.
+ *
+ * @param the type of state that this listener will handle
+ */
+public interface StateListener {
+
+ /**
+ * This method is called when the state has changed.
+ *
+ * @param state the updated state
+ */
+ void onStateChange(T state);
+}
diff --git a/bloc/src/test/java/com/iluwatar/bloc/BlocTest.java b/bloc/src/test/java/com/iluwatar/bloc/BlocTest.java
new file mode 100644
index 000000000000..98e34b8d4a22
--- /dev/null
+++ b/bloc/src/test/java/com/iluwatar/bloc/BlocTest.java
@@ -0,0 +1,85 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class BlocTest {
+ private Bloc bloc;
+ private AtomicInteger stateValue;
+
+ @BeforeEach
+ void setUp() {
+ bloc = new Bloc();
+ stateValue = new AtomicInteger(0);
+ }
+
+ @Test
+ void initialState() {
+ assertTrue(bloc.getListeners().isEmpty(), "No listeners should be present initially.");
+ }
+
+ @Test
+ void IncrementUpdateState() {
+ bloc.addListener(state -> stateValue.set(state.value()));
+ bloc.increment();
+ assertEquals(1, stateValue.get(), "State should increment to 1");
+ }
+
+ @Test
+ void DecrementUpdateState() {
+ bloc.addListener(state -> stateValue.set(state.value()));
+ bloc.decrement();
+ assertEquals(-1, stateValue.get(), "State should decrement to -1");
+ }
+
+ @Test
+ void addingListener() {
+ bloc.addListener(state -> {});
+ assertEquals(1, bloc.getListeners().size(), "Listener count should be 1.");
+ }
+
+ @Test
+ void removingListener() {
+ StateListener listener = state -> {};
+ bloc.addListener(listener);
+ bloc.removeListener(listener);
+ assertTrue(bloc.getListeners().isEmpty(), "Listener count should be 0 after removal.");
+ }
+
+ @Test
+ void multipleListeners() {
+ AtomicInteger secondValue = new AtomicInteger();
+ bloc.addListener(state -> stateValue.set(state.value()));
+ bloc.addListener(state -> secondValue.set(state.value()));
+ bloc.increment();
+ assertEquals(1, stateValue.get(), "First listener should receive state 1.");
+ assertEquals(1, secondValue.get(), "Second listener should receive state 1.");
+ }
+}
diff --git a/bloc/src/test/java/com/iluwatar/bloc/BlocUiTest.java b/bloc/src/test/java/com/iluwatar/bloc/BlocUiTest.java
new file mode 100644
index 000000000000..f1fc73947896
--- /dev/null
+++ b/bloc/src/test/java/com/iluwatar/bloc/BlocUiTest.java
@@ -0,0 +1,121 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.bloc;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.awt.*;
+import javax.swing.*;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class BlocUiTest {
+
+ private JFrame frame;
+ private JLabel counterLabel;
+ private JButton incrementButton;
+ private JButton decrementButton;
+ private JButton toggleListenerButton;
+ private Bloc bloc;
+ private StateListener stateListener;
+
+ @BeforeEach
+ void setUp() {
+ bloc = new Bloc(); // Re-initialize the Bloc for each test
+
+ frame = new JFrame("BloC example");
+ frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
+ frame.setSize(400, 300);
+
+ counterLabel = new JLabel("Counter: 0", SwingConstants.CENTER);
+ counterLabel.setFont(new Font("Arial", Font.BOLD, 20));
+
+ incrementButton = new JButton("Increment");
+ decrementButton = new JButton("Decrement");
+ toggleListenerButton = new JButton("Disable Listener");
+
+ frame.setLayout(new BorderLayout());
+ frame.add(counterLabel, BorderLayout.CENTER);
+ frame.add(incrementButton, BorderLayout.NORTH);
+ frame.add(decrementButton, BorderLayout.SOUTH);
+ frame.add(toggleListenerButton, BorderLayout.EAST);
+
+ stateListener = state -> counterLabel.setText("Counter: " + state.value());
+ bloc.addListener(stateListener);
+
+ incrementButton.addActionListener(e -> bloc.increment());
+ decrementButton.addActionListener(e -> bloc.decrement());
+ toggleListenerButton.addActionListener(
+ e -> {
+ if (bloc.getListeners().contains(stateListener)) {
+ bloc.removeListener(stateListener);
+ toggleListenerButton.setText("Enable Listener");
+ } else {
+ bloc.addListener(stateListener);
+ toggleListenerButton.setText("Disable Listener");
+ }
+ });
+
+ frame.setVisible(true);
+ }
+
+ @AfterEach
+ void tearDown() {
+ frame.dispose();
+ bloc = new Bloc(); // Reset Bloc state after each test to avoid state carryover
+ }
+
+ @Test
+ void testIncrementButton() {
+ simulateButtonClick(incrementButton);
+ assertEquals("Counter: 1", counterLabel.getText());
+ }
+
+ @Test
+ void testDecrementButton() {
+ simulateButtonClick(decrementButton);
+ assertEquals("Counter: -1", counterLabel.getText());
+ }
+
+ @Test
+ void testToggleListenerButton() {
+ // Disable listener
+ simulateButtonClick(toggleListenerButton);
+ simulateButtonClick(incrementButton);
+ assertEquals("Counter: 0", counterLabel.getText()); // Listener is disabled
+
+ // Enable listener
+ simulateButtonClick(toggleListenerButton);
+ simulateButtonClick(incrementButton);
+ assertEquals("Counter: 2", counterLabel.getText()); // Listener is re-enabled
+ }
+
+ private void simulateButtonClick(JButton button) {
+ for (var listener : button.getActionListeners()) {
+ listener.actionPerformed(null);
+ }
+ }
+}
diff --git a/bridge/README.md b/bridge/README.md
index ebd6e5b41e20..26567b292c81 100644
--- a/bridge/README.md
+++ b/bridge/README.md
@@ -1,197 +1,256 @@
---
-layout: pattern
-title: Bridge
-folder: bridge
-permalink: /patterns/bridge/
-categories: Structural
-tags:
- - Gang of Four
+title: "Bridge Pattern in Java: Decouple Abstraction from Implementation"
+shortTitle: Bridge
+description: "Learn about the Bridge design pattern in Java. Decouple abstraction from implementation to enhance flexibility and extensibility. Explore real-world examples, class diagrams, and use cases."
+category: Structural
+language: en
+tag:
+ - Abstraction
+ - Decoupling
+ - Extensibility
+ - Gang of Four
+ - Object composition
---
## Also known as
-Handle/Body
-## Intent
-Decouple an abstraction from its implementation so that the two can vary independently.
+* Handle/Body
-## Explanation
+## Intent of Bridge Design Pattern
-Real world example
+The Bridge design pattern is a structural pattern in Java that decouples an abstraction from its implementation, allowing both to vary independently. This pattern is essential for developing flexible and extensible software systems.
-> Consider you have a weapon with different enchantments and you are supposed to allow mixing different weapons with different enchantments. What would you do? Create multiple copies of each of the weapons for each of the enchantments or would you just create separate enchantment and set it for the weapon as needed? Bridge pattern allows you to do the second.
+## Detailed Explanation of Bridge Pattern with Real-World Examples
+
+Real-world example
+
+> In Java, the Bridge pattern is commonly used in GUI frameworks, database drivers, and device drivers. For instance, a universal remote control (abstraction) can operate various TV brands (implementations) through a consistent interface.
+>
+> Imagine a universal remote control (abstraction) that can operate different brands and types of televisions (implementations). The remote control provides a consistent interface for operations like turning on/off, changing channels, and adjusting the volume. Each television brand or type has its own specific implementation of these operations. By using the Bridge pattern, the remote control interface is decoupled from the television implementations, allowing the remote control to work with any television regardless of its brand or internal workings. This separation allows new television models to be added without changing the remote control's code, and different remote controls can be developed to work with the same set of televisions.
In Plain Words
-> Bridge pattern is about preferring composition over inheritance. Implementation details are pushed from a hierarchy to another object with a separate hierarchy.
+> Bridge pattern is about preferring composition to inheritance. Implementation details are pushed from a hierarchy to another object with a separate hierarchy.
Wikipedia says
> The bridge pattern is a design pattern used in software engineering that is meant to "decouple an abstraction from its implementation so that the two can vary independently"
-**Programmatic Example**
+Sequence diagram
+
+
+
+## Programmatic Example of Bridge Pattern in Java
-Translating our weapon example from above. Here we have the `Weapon` hierarchy
+Imagine you have a weapon that can have various enchantments, and you need to combine different weapons with different enchantments. How would you handle this? Would you create multiple copies of each weapon, each with a different enchantment, or would you create separate enchantments and apply them to the weapon as needed? The Bridge pattern enables you to do the latter.
+
+Here we have the `Weapon` hierarchy:
```java
public interface Weapon {
- void wield();
- void swing();
- void unwield();
- Enchantment getEnchantment();
+ void wield();
+
+ void swing();
+
+ void unwield();
+
+ Enchantment getEnchantment();
}
public class Sword implements Weapon {
- private final Enchantment enchantment;
-
- public Sword(Enchantment enchantment) {
- this.enchantment = enchantment;
- }
-
- @Override
- public void wield() {
- LOGGER.info("The sword is wielded.");
- enchantment.onActivate();
- }
-
- @Override
- public void swing() {
- LOGGER.info("The sword is swinged.");
- enchantment.apply();
- }
-
- @Override
- public void unwield() {
- LOGGER.info("The sword is unwielded.");
- enchantment.onDeactivate();
- }
-
- @Override
- public Enchantment getEnchantment() {
- return enchantment;
- }
+ private final Enchantment enchantment;
+
+ public Sword(Enchantment enchantment) {
+ this.enchantment = enchantment;
+ }
+
+ @Override
+ public void wield() {
+ LOGGER.info("The sword is wielded.");
+ enchantment.onActivate();
+ }
+
+ @Override
+ public void swing() {
+ LOGGER.info("The sword is swung.");
+ enchantment.apply();
+ }
+
+ @Override
+ public void unwield() {
+ LOGGER.info("The sword is unwielded.");
+ enchantment.onDeactivate();
+ }
+
+ @Override
+ public Enchantment getEnchantment() {
+ return enchantment;
+ }
}
public class Hammer implements Weapon {
- private final Enchantment enchantment;
-
- public Hammer(Enchantment enchantment) {
- this.enchantment = enchantment;
- }
-
- @Override
- public void wield() {
- LOGGER.info("The hammer is wielded.");
- enchantment.onActivate();
- }
-
- @Override
- public void swing() {
- LOGGER.info("The hammer is swinged.");
- enchantment.apply();
- }
-
- @Override
- public void unwield() {
- LOGGER.info("The hammer is unwielded.");
- enchantment.onDeactivate();
- }
-
- @Override
- public Enchantment getEnchantment() {
- return enchantment;
- }
+ private final Enchantment enchantment;
+
+ public Hammer(Enchantment enchantment) {
+ this.enchantment = enchantment;
+ }
+
+ @Override
+ public void wield() {
+ LOGGER.info("The hammer is wielded.");
+ enchantment.onActivate();
+ }
+
+ @Override
+ public void swing() {
+ LOGGER.info("The hammer is swung.");
+ enchantment.apply();
+ }
+
+ @Override
+ public void unwield() {
+ LOGGER.info("The hammer is unwielded.");
+ enchantment.onDeactivate();
+ }
+
+ @Override
+ public Enchantment getEnchantment() {
+ return enchantment;
+ }
}
```
-And the separate enchantment hierarchy
+Here's the separate `Enchantment` hierarchy:
```java
public interface Enchantment {
- void onActivate();
- void apply();
- void onDeactivate();
+ void onActivate();
+
+ void apply();
+
+ void onDeactivate();
}
public class FlyingEnchantment implements Enchantment {
- @Override
- public void onActivate() {
- LOGGER.info("The item begins to glow faintly.");
- }
+ @Override
+ public void onActivate() {
+ LOGGER.info("The item begins to glow faintly.");
+ }
- @Override
- public void apply() {
- LOGGER.info("The item flies and strikes the enemies finally returning to owner's hand.");
- }
+ @Override
+ public void apply() {
+ LOGGER.info("The item flies and strikes the enemies finally returning to owner's hand.");
+ }
- @Override
- public void onDeactivate() {
- LOGGER.info("The item's glow fades.");
- }
+ @Override
+ public void onDeactivate() {
+ LOGGER.info("The item's glow fades.");
+ }
}
public class SoulEatingEnchantment implements Enchantment {
- @Override
- public void onActivate() {
- LOGGER.info("The item spreads bloodlust.");
- }
+ @Override
+ public void onActivate() {
+ LOGGER.info("The item spreads bloodlust.");
+ }
- @Override
- public void apply() {
- LOGGER.info("The item eats the soul of enemies.");
- }
+ @Override
+ public void apply() {
+ LOGGER.info("The item eats the soul of enemies.");
+ }
- @Override
- public void onDeactivate() {
- LOGGER.info("Bloodlust slowly disappears.");
- }
+ @Override
+ public void onDeactivate() {
+ LOGGER.info("Bloodlust slowly disappears.");
+ }
}
```
-And both the hierarchies in action
+Here are both hierarchies in action:
```java
-var enchantedSword = new Sword(new SoulEatingEnchantment());
-enchantedSword.wield();
-enchantedSword.swing();
-enchantedSword.unwield();
-// The sword is wielded.
-// The item spreads bloodlust.
-// The sword is swinged.
-// The item eats the soul of enemies.
-// The sword is unwielded.
-// Bloodlust slowly disappears.
-
-var hammer = new Hammer(new FlyingEnchantment());
-hammer.wield();
-hammer.swing();
-hammer.unwield();
-// The hammer is wielded.
-// The item begins to glow faintly.
-// The hammer is swinged.
-// The item flies and strikes the enemies finally returning to owner's hand.
-// The hammer is unwielded.
-// The item's glow fades.
+public static void main(String[] args) {
+ LOGGER.info("The knight receives an enchanted sword.");
+ var enchantedSword = new Sword(new SoulEatingEnchantment());
+ enchantedSword.wield();
+ enchantedSword.swing();
+ enchantedSword.unwield();
+
+ LOGGER.info("The valkyrie receives an enchanted hammer.");
+ var hammer = new Hammer(new FlyingEnchantment());
+ hammer.wield();
+ hammer.swing();
+ hammer.unwield();
+}
```
-## Class diagram
-
+Here's the console output.
+
+```
+The knight receives an enchanted sword.
+The sword is wielded.
+The item spreads bloodlust.
+The sword is swung.
+The item eats the soul of enemies.
+The sword is unwielded.
+Bloodlust slowly disappears.
+The valkyrie receives an enchanted hammer.
+The hammer is wielded.
+The item begins to glow faintly.
+The hammer is swung.
+The item flies and strikes the enemies finally returning to owner's hand.
+The hammer is unwielded.
+The item's glow fades.
+```
+
+## When to Use the Bridge Pattern in Java
+
+Consider using the Bridge pattern when:
+
+* You need to avoid a permanent binding between an abstraction and its implementation, such as when the implementation must be chosen or switched at runtime.
+* Both the abstractions and their implementations should be extendable via subclassing, allowing independent extension of each component.
+* Changes to the implementation of an abstraction should not affect clients, meaning their code should not require recompilation.
+* You encounter a large number of classes in your hierarchy, indicating the need to split an object into two parts, a concept referred to as "nested generalizations" by Rumbaugh.
+* You want to share an implementation among multiple objects, potentially using reference counting, while keeping this detail hidden from the client, as exemplified by Coplien's String class, where multiple objects can share the same string representation.
+
+## Bridge Pattern Java Tutorials
+
+* [Bridge Pattern Tutorial (DigitalOcean)](https://www.digitalocean.com/community/tutorials/bridge-design-pattern-java)
+
+## Real-World Applications of Bridge Pattern in Java
+
+* GUI Frameworks where the abstraction is the window, and the implementation could be the underlying OS windowing system.
+* Database Drivers where the abstraction is a generic database interface, and the implementations are database-specific drivers.
+* Device Drivers where the abstraction is the device-independent code, and the implementation is the device-dependent code.
+
+## Benefits and Trade-offs of Bridge Pattern
+
+Benefits:
+
+* Decoupling Interface and Implementation: The Bridge pattern enhances modularity by separating the interface (the high-level operations) from the implementation (the low-level operations).
+* Improved Extensibility: You can extend the abstraction and implementation hierarchies independently.
+* Hiding Implementation Details: Clients only see the abstraction's interface, not its implementation.
+
+Trade-offs:
-## Applicability
-Use the Bridge pattern when
+* Increased Complexity: The pattern can complicate the system architecture and code, especially for clients unfamiliar with the pattern.
+* Runtime Overhead: The extra layer of abstraction can introduce a performance penalty, although it is often negligible in practice.
-* you want to avoid a permanent binding between an abstraction and its implementation. This might be the case, for example, when the implementation must be selected or switched at run-time.
-* both the abstractions and their implementations should be extensible by subclassing. In this case, the Bridge pattern lets you combine the different abstractions and implementations and extend them independently
-* changes in the implementation of an abstraction should have no impact on clients; that is, their code should not have to be recompiled.
-* you have a proliferation of classes. Such a class hierarchy indicates the need for splitting an object into two parts. Rumbaugh uses the term "nested generalizations" to refer to such class hierarchies
-* you want to share an implementation among multiple objects (perhaps using reference counting), and this fact should be hidden from the client. A simple example is Coplien's String class, in which multiple objects can share the same string representation.
+## Related Java Design Patterns
-## Tutorial
-* [Bridge Pattern Tutorial](https://www.journaldev.com/1491/bridge-design-pattern-java)
+* [Abstract Factory](https://java-design-patterns.com/patterns/abstract-factory/): The Abstract Factory pattern can be used along with the Bridge pattern to create platforms that are independent of the concrete classes used to create their objects.
+* [Adapter](https://java-design-patterns.com/patterns/adapter/): The Adapter pattern is used to provide a different interface to an object, while the Bridge pattern is used to separate an object's interface from its implementation.
+* [Composite](https://java-design-patterns.com/patterns/composite/): The Bridge pattern is often used with the Composite pattern to model the implementation details of a component.
+* [Strategy](https://java-design-patterns.com/patterns/strategy/): The Strategy pattern is like the Bridge pattern, but with a different intent. Both patterns are based on composition: Strategy uses composition to change the behavior of a class, while Bridge uses composition to separate an abstraction from its implementation.
-## Credits
+## References and Credits
-* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
+* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
+* [Head First Design Patterns: Building Extensible and Maintainable Object-Oriented Software](https://amzn.to/49NGldq)
+* [Java Design Patterns: A Hands-On Experience with Real-World Examples](https://amzn.to/3yhh525)
+* [Pattern-Oriented Software Architecture Volume 1: A System of Patterns](https://amzn.to/3TEnhtl)
+* [Patterns of Enterprise Application Architecture](https://amzn.to/3WfKBPR)
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-
-
-
