001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.zookeeper;
019
020import org.apache.yetus.audience.InterfaceAudience;
021
022/**
023 * Base class for internal listeners of ZooKeeper events. The {@link ZKWatcher} for a process will
024 * execute the appropriate methods of implementations of this class. In order to receive events from
025 * the watcher, every listener must register itself via {@link ZKWatcher#registerListener}.
026 * Subclasses need only override those methods in which they are interested. Note that the watcher
027 * will be blocked when invoking methods in listeners so they must not be long-running.
028 */
029@InterfaceAudience.Private
030public abstract class ZKListener {
031
032  // Reference to the zk watcher which also contains configuration and constants
033  protected ZKWatcher watcher;
034
035  /**
036   * Construct a ZooKeeper event listener.
037   */
038  public ZKListener(ZKWatcher watcher) {
039    this.watcher = watcher;
040  }
041
042  /**
043   * Called when a new node has been created.
044   * @param path full path of the new node
045   */
046  public void nodeCreated(String path) {
047    // no-op
048  }
049
050  /**
051   * Called when a node has been deleted
052   * @param path full path of the deleted node
053   */
054  public void nodeDeleted(String path) {
055    // no-op
056  }
057
058  /**
059   * Called when an existing node has changed data.
060   * @param path full path of the updated node
061   */
062  public void nodeDataChanged(String path) {
063    // no-op
064  }
065
066  /**
067   * Called when an existing node has a child node added or removed.
068   * @param path full path of the node whose children have changed
069   */
070  public void nodeChildrenChanged(String path) {
071    // no-op
072  }
073
074  /** Returns The watcher associated with this listener */
075  public ZKWatcher getWatcher() {
076    return this.watcher;
077  }
078}