DATACMNS-928 - Support for publishing events from aggregate roots.

Introduced @DomainEvents usable on a method of an aggregate root. The method will be invoked when the aggregate is passed to a repository to save and its returned value or values will be exposed via an ApplicationEventListener.

Also, the aggregate can expose a method annotated with @AfterDomainEventPublication which will be invoked once all events have been published.

src/main/java/org/springframework/data/domain/AbstractAggregateRoot.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2016 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.springframework.data.domain;
+
+import lombok.Getter;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author Oliver Gierke
+ */
+public class AbstractAggregateRoot {
+
+	private transient final @Getter(onMethod = @__(@DomainEvents)) List<Object> domainEvents = new ArrayList<Object>();
+
+	protected <T> T registerEvent(T event) {
+
+		this.domainEvents.add(event);
+		return event;
+	}
+
+	@AfterDomainEventPublication
+	public void clearDomainEvents() {
+		this.domainEvents.clear();
+	}
+}

src/main/java/org/springframework/data/domain/AfterDomainEventPublication.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2016 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.springframework.data.domain;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation to be used on a method of a Spring Data managed aggregate to get invoked after the events of an aggregate
+ * have been published.
+ * 
+ * @author Oliver Gierke
+ * @see DomainEvents
+ * @soundtrack Benny Greb - September (Moving Parts Live)
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
+public @interface AfterDomainEventPublication {
+
+}

src/main/java/org/springframework/data/domain/DomainEvents.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2016 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.springframework.data.domain;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.ApplicationEventPublisher;
+
+/**
+ * {@link DomainEvents} can be used on methods of aggregate roots managed by Spring Data repositories to publish the
+ * events returned by that method as Spring application events.
+ * 
+ * @author Oliver Gierke
+ * @see ApplicationEventPublisher
+ * @see AfterDomainEventPublication
+ * @soundtrack Benny Greb - Soulfood (Moving Parts Live)
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
+public @interface DomainEvents {
+}