Introduce the abstract MembershipEvent class to encapsulate the details of a membership event (e.g. memberJoined event) as defined by the o.a.g.distributed.internal.MembershipListener interface.

apache-geode-extensions/src/main/java/org/springframework/geode/distributed/event/MembershipEvent.java

@@ -0,0 +1,161 @@
+/*
+ * 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
+ *
+ *     https://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.geode.distributed.event;
+
+import java.util.EventObject;
+import java.util.Optional;
+
+import org.apache.geode.cache.Cache;
+import org.apache.geode.distributed.DistributedMember;
+import org.apache.geode.distributed.DistributedSystem;
+import org.apache.geode.distributed.internal.DistributionManager;
+
+/**
+ * {@link EventObject} implementation indicating a membership event in the {@link DistributedSystem}.
+ *
+ * @author John Blum
+ * @param <T> specific {@link Class type} of {@link MembershipEvent}.
+ * @see java.util.EventObject
+ * @see org.apache.geode.cache.Cache
+ * @see org.apache.geode.distributed.DistributedMember
+ * @see org.apache.geode.distributed.DistributedSystem
+ * @see org.apache.geode.distributed.internal.DistributionManager
+ * @since 1.3.0
+ */
+@SuppressWarnings("unused")
+public abstract class MembershipEvent<T extends MembershipEvent<T>> extends EventObject {
+
+	private DistributedMember distributedMember;
+
+	/**
+	 * Asserts that the given {@link Object target} is not {@literal null}.
+	 *
+	 * @param <T> {@link Class type} of the {@link Object target}.
+	 * @param target {@link Object} to evaluate.
+	 * @param message {@link String} containing the message for the {@link IllegalArgumentException}.
+	 * @param arguments array of {@link Object arguments} to populate the placeholders in the {@link String message}.
+	 * @return the {@link Object target}.
+	 * @throws IllegalArgumentException if {@link Object target} is {@literal null}.
+	 */
+	protected static <T> T assertNotNull(T target, String message, Object... arguments) {
+
+		if (target == null) {
+			throw new IllegalArgumentException(String.format(message, arguments));
+		}
+
+		return target;
+	}
+
+	/**
+	 * Constructs a new instance of {@link MembershipEvent} initialized with the given {@link DistributionManager}.
+	 *
+	 * @param distributionManager {@link DistributionManager} used to acquire the {@link Cache}, which is used
+	 * as the {@literal source} of this event.
+	 * @throws IllegalArgumentException if {@link DistributionManager} is {@literal null}.
+	 * @see org.apache.geode.distributed.internal.DistributionManager
+	 */
+	public MembershipEvent(DistributionManager distributionManager) {
+		super(assertNotNull(distributionManager, "DistributionManager must not be null"));
+	}
+
+	/**
+	 * Returns an {@link Optional} reference to the {@literal peer} {@link Cache}.
+	 *
+	 * @return an {@link Optional} reference to the {@literal peer} {@link Cache}.
+	 * @see org.apache.geode.cache.Cache
+	 * @see #getDistributionManager()
+	 * @see java.util.Optional
+	 */
+	public Optional<Cache> getCache() {
+		return Optional.ofNullable(getDistributionManager().getCache());
+	}
+
+	/**
+	 * Returns an {@link Optional} reference to the {@link DistributedMember} that is the subject
+	 * of this {@link MembershipEvent}.
+	 *
+	 * @return an {@link Optional} reference to the {@link DistributedMember} that is the subject of this event.
+	 * @see org.apache.geode.distributed.DistributedMember
+	 * @see #getDistributionManager()
+	 * @see java.util.Optional
+	 */
+	public Optional<DistributedMember> getDistributedMember() {
+		return Optional.ofNullable(this.distributedMember);
+	}
+
+	/**
+	 * Returns an {@link Optional} reference to the {@link DistributedSystem} (cluster) to which the {@literal peer}
+	 * {@link Cache} is connected.
+	 *
+	 * @return an {@link Optional} reference to the {@link DistributedSystem}.
+	 * @see org.apache.geode.distributed.DistributedSystem
+	 * @see #getDistributionManager()
+	 * @see java.util.Optional
+	 */
+	public Optional<DistributedSystem> getDistributedSystem() {
+		return Optional.ofNullable(getDistributionManager().getSystem());
+	}
+
+	/**
+	 * Returns a reference to the configured {@link DistributionManager} which is use as the {@link #getSource() source}
+	 * of this event.
+	 *
+	 * @return a reference to the {@link DistributionManager}.
+	 * @see org.apache.geode.distributed.internal.DistributionManager
+	 */
+	public DistributionManager getDistributionManager() {
+		return (DistributionManager) getSource();
+	}
+
+	/**
+	 * Returns the {@link Type} of this {@link MembershipEvent}, such as {@link Type#MEMBER_JOINED}.
+	 *
+	 * @return the {@link MembershipEvent.Type}.
+	 */
+	public Type getType() {
+		return Type.UNQUALIFIED;
+	}
+
+	/**
+	 * Null-safe builder method used to configure the {@link DistributedMember member} that is the subject
+	 * of this event.
+	 *
+	 * @param distributedMember {@link DistributedMember} that is the subject of this event.
+	 * @return this {@link MembershipEvent}.
+	 * @see org.apache.geode.distributed.DistributedMember
+	 * @see #getDistributedMember()
+	 */
+	@SuppressWarnings("unchecked")
+	public T withMember(DistributedMember distributedMember) {
+
+		this.distributedMember = distributedMember;
+
+		return (T) this;
+	}
+
+	/**
+	 * An {@link Enum enumeration} of different type of {@link MembershipEvent MembershipEvents}.
+	 */
+	public enum Type {
+
+		MEMBER_DEPARTED,
+		MEMBER_JOINED,
+		MEMBER_SUSPECT,
+		QUORUM_LOST,
+		UNQUALIFIED;
+
+	}
+}