GH-33 First version of port of AbstractEntity from DDDBITS

jmolecules-ddd/pom.xml

@@ -13,6 +13,20 @@
 	<name>jMolecules - DDD</name>
 
 	<dependencies>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-engine</artifactId>
+			<version>${junit.version}</version>
+			<scope>test</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>org.assertj</groupId>
+			<artifactId>assertj-core</artifactId>
+			<version>${assertj.version}</version>
+			<scope>test</scope>
+		</dependency>
+
 		<dependency>
 			<groupId>org.projectlombok</groupId>
 			<artifactId>lombok</artifactId>

jmolecules-ddd/src/main/java/org/jmolecules/ddd/types/AbstractEntity.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jmolecules.ddd.types;
+
+/**
+ * An abstract base for entities.
+ * Provides implementations for {@code equals()}, {@code hashCode()}, and {@code toString()} that are based on the identity of the entity.
+ */
+@org.jmolecules.ddd.annotation.Entity
+public abstract class AbstractEntity<R extends AggregateRoot<R, ?>, ID> implements Entity<R, ID> {
+
+	private final ID identity;
+
+	protected AbstractEntity(ID identity) {
+		if (identity == null) {
+			throw new IllegalArgumentException("identity must not be null");
+		}
+
+		this.identity = identity;
+	}
+
+	@Override
+	public final ID getId() {
+		return identity;
+	}
+
+	@Override
+	public String toString() {
+		return getClass().getSimpleName() + " [id=" + identity + "]";
+	}
+
+	@Override
+	public final boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (obj == null)
+			return false;
+		if (getClass() != obj.getClass())
+			return false;
+		@SuppressWarnings("rawtypes")
+		AbstractEntity other = (AbstractEntity) obj;
+		if (identity == null) {
+			if (other.identity != null)
+				return false;
+		} else if (!identity.equals(other.identity))
+			return false;
+		return true;
+	}
+
+	@Override
+	public final int hashCode() {
+		return identity.hashCode();
+	}
+
+}

jmolecules-ddd/src/test/java/org/jmolecules/ddd/types/AbstractEntityTest.java

@@ -0,0 +1,85 @@
+package org.jmolecules.ddd.types;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+import lombok.Value;
+
+class AbstractEntityTest {
+
+	@Value
+    static class Id implements Identifier {
+
+        long id;
+
+        public static Id of(long id) {
+            return new Id(id);
+		}
+
+		public String toString() {
+			return "" + id;
+		}
+
+    }
+
+	static class ConcreteEntity extends AbstractEntity<ConcreteEntity, Id> implements AggregateRoot<ConcreteEntity, Id> {
+
+		public ConcreteEntity(Id id) {
+			super(id);
+        }
+
+	}
+
+	@Test
+	void givenANewEntity_whenGetId_thenEqual() {
+		// given
+		ConcreteEntity entityUnderTest = new ConcreteEntity(Id.of(47L)) {
+		};
+
+		// when
+		Id id = entityUnderTest.getId();
+
+		// then
+		assertThat(id).isEqualTo(Id.of(47L));
+	}
+
+	@Test
+	void givenTwoEntitiesOfSameTypeWithSameId_whenEquals_thenTrue() {
+		// given
+		ConcreteEntity entity1 = new ConcreteEntity(Id.of(47L));
+		ConcreteEntity entity2 = new ConcreteEntity(Id.of(47L));
+
+		// when
+		boolean equal = entity1.equals(entity2);
+
+		// then
+		assertThat(equal).isTrue();
+	}
+
+	@Test
+	void givenTwoEntitiesOfDifferentTypeWithSameId_whenEquals_thenFalse() {
+		// given
+		ConcreteEntity entity1 = new ConcreteEntity(Id.of(47L)) { };
+		ConcreteEntity entity2 = new ConcreteEntity(Id.of(47L)) { };
+
+		// when
+		boolean equal = entity1.equals(entity2);
+
+		// then
+		assertThat(equal).isFalse();
+	}
+
+	@Test
+	void givenAnEntity_whenToString_thenClassnamePlusId() {
+		// given
+		ConcreteEntity entityUnderTest = new ConcreteEntity(Id.of(47L));
+
+		// when
+		String string = entityUnderTest.toString();
+
+		// then
+		assertThat(string).isEqualTo("ConcreteEntity [id=47]");
+	}
+
+}