/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to You 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.apache.geode.cache;

/**
 * Interface <code>InterestRegisterationListener</code> provides the ability for applications to be
 * notified of interest registration and unregistration events. Instances must be implemented by
 * applications and registered in <code>CacheServer</code> VMs using the
 * {@link org.apache.geode.cache.server.CacheServer#registerInterestRegistrationListener
 * registerInterestRegistrationListener} API. The methods on an
 * <code>InterestRegisterationListener</code> are invoked synchronously with the interest event in
 * any <code>CacheServer</code> VM hosting the requesting client's subscriptions.
 *
 * <p>
 * Shown below is an example implementation.
 *
 * <pre>
 * import org.apache.geode.cache.InterestRegistrationEvent;
 * import org.apache.geode.cache.InterestRegistrationListener;
 *
 * public class TestInterestRegistrationListener implements InterestRegistrationListener {
 *
 *   public void afterRegisterInterest(InterestRegistrationEvent event) {
 *     System.out.println(
 *         "afterRegisterInterest: " + event.getRegionName() + " -> " + event.getKeysOfInterest());
 *   }
 *
 *   public void afterUnregisterInterest(InterestRegistrationEvent event) {
 *     System.out.println("afterUnregisterInterest: " + event.getRegionName() + " -> "
 *         + event.getKeysOfInterest());
 *   }
 *
 *   public void close() {}
 * }
 * </pre>
 *
 * Shown below is an example registration.
 *
 * <pre>
 *private void registerInterestRegistrationListener() {
 *  Cache cache = ...;
 *  CacheServer cs = cache.getCacheServers().iterator().next();
 *  InterestRegistrationListener listener = new TestInterestRegistrationListener();
 *  cs.registerInterestRegistrationListener(listener);
 *}
 * </pre>
 *
 *
 * @since GemFire 6.0
 *
 * @see org.apache.geode.cache.server.CacheServer#registerInterestRegistrationListener
 *      registerInterestRegistrationListener
 * @see org.apache.geode.cache.server.CacheServer#unregisterInterestRegistrationListener
 *      unregisterInterestRegistrationListener
 */
public interface InterestRegistrationListener extends CacheCallback {

  /**
   * Handles an after register interest event.
   *
   * @param event the InterestRegistrationEvent
   */
  void afterRegisterInterest(InterestRegistrationEvent event);

  /**
   * Handles an after unregister interest event.
   *
   * @param event the InterestRegistrationEvent
   */
  void afterUnregisterInterest(InterestRegistrationEvent event);
}