Example Showcase: Domain Events

src/main/java/com/classvar/examples/ExampleCommandProcessor.java

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+package com.classvar.examples;
+
+import org.springframework.stereotype.Service;
+
+import javax.transaction.Transactional;
+
+@Service
+public class ExampleCommandProcessor {
+
+    private ExampleRepository exampleRepository;
+
+    public ExampleCommandProcessor(ExampleRepository exampleRepository) {
+        this.exampleRepository = exampleRepository;
+    }
+
+    @Transactional
+    public void doExampleOperation() {
+        ExampleEntity toCreate = new ExampleEntity("name");
+        exampleRepository.save(toCreate);
+    }
+}

src/main/java/com/classvar/examples/ExampleEntity.java

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+package com.classvar.examples;
+
+import org.springframework.data.domain.AbstractAggregateRoot;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity
+public class ExampleEntity extends AbstractAggregateRoot<ExampleEntity> {
+
+    // MySQL
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    private String name;
+
+    protected ExampleEntity() {}
+
+    public ExampleEntity(String name) {
+        this.name = name;
+        this.registerEvent(new ExampleEntityCreated(this));
+    }
+
+    public String getName() {
+        return this.name;
+    }
+}

src/main/java/com/classvar/examples/ExampleEntityCreated.java

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+package com.classvar.examples;
+
+public class ExampleEntityCreated {
+
+    private ExampleEntity entity;
+
+    public ExampleEntityCreated(ExampleEntity entity) {
+        this.entity = entity;
+    }
+
+    public ExampleEntity getEntity() {
+        return this.entity;
+    }
+}

src/main/java/com/classvar/examples/ExampleEventListener.java

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+package com.classvar.examples;
+
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+
+@Component
+public class ExampleEventListener {
+
+    @EventListener
+    public void handle(ExampleEntityCreated event) {
+        // ... do something ...
+    }
+}

src/main/java/com/classvar/examples/ExampleRepository.java

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+package com.classvar.examples;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface ExampleRepository extends JpaRepository<ExampleEntity, Long> {
+}

src/test/java/com/classvar/examples/ExampleEntityDomainEventTest.java

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+package com.classvar.examples;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.mock.mockito.MockBean;
+
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+@SpringBootTest
+public class ExampleEntityDomainEventTest {
+
+    @Autowired
+    ExampleCommandProcessor processor;
+
+    @MockBean
+    ExampleEventListener listener;
+
+    @Test
+    public void DomainEventIsPublishedAfterTransaction() {
+        processor.doExampleOperation();
+
+        verify(listener, times(1)).handle(Mockito.isA(ExampleEntityCreated.class));
+    }
+}