Add BAEL-2067 DomainEvents examples

spring-data-jpa/src/main/java/com/baeldung/ddd/event/DomainService.java

@@ -0,0 +1,31 @@
+/**
+ *
+ */
+package com.baeldung.ddd.event;
+
+import javax.transaction.Transactional;
+
+import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.stereotype.Service;
+
+@Service
+public class DomainService {
+    private final ApplicationEventPublisher eventPublisher;
+    private final AggregateRepository repository;
+
+    public DomainService(AggregateRepository repository, ApplicationEventPublisher eventPublisher) {
+        this.repository = repository;
+        this.eventPublisher = eventPublisher;
+    }
+
+    @Transactional
+    public void serviceDomainOperation(long entityId) {
+        repository.findById(entityId)
+            .ifPresent(entity -> {
+                entity.domainOperation();
+                repository.save(entity);
+                eventPublisher.publishEvent(new DomainEvent());
+            });
+    }
+
+}