1 /** 2 * Copyright 2010 The Apache Software Foundation 3 * 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, 16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 */ 20 package org.apache.hadoop.hbase.zookeeper; 21 22 23 /** 24 * Base class for internal listeners of ZooKeeper events. 25 * 26 * The {@link ZooKeeperWatcher} for a process will execute the appropriate 27 * methods of implementations of this class. In order to receive events from 28 * the watcher, every listener must register itself via {@link ZooKeeperWatcher#registerListener}. 29 * 30 * Subclasses need only override those methods in which they are interested. 31 * 32 * Note that the watcher will be blocked when invoking methods in listeners so 33 * they must not be long-running. 34 */ 35 public class ZooKeeperListener { 36 37 // Reference to the zk watcher which also contains configuration and constants 38 protected ZooKeeperWatcher watcher; 39 40 /** 41 * Construct a ZooKeeper event listener. 42 */ 43 public ZooKeeperListener(ZooKeeperWatcher watcher) { 44 this.watcher = watcher; 45 } 46 47 /** 48 * Called when a new node has been created. 49 * @param path full path of the new node 50 */ 51 public void nodeCreated(String path) { 52 // no-op 53 } 54 55 /** 56 * Called when a node has been deleted 57 * @param path full path of the deleted node 58 */ 59 public void nodeDeleted(String path) { 60 // no-op 61 } 62 63 /** 64 * Called when an existing node has changed data. 65 * @param path full path of the updated node 66 */ 67 public void nodeDataChanged(String path) { 68 // no-op 69 } 70 71 /** 72 * Called when an existing node has a child node added or removed. 73 * @param path full path of the node whose children have changed 74 */ 75 public void nodeChildrenChanged(String path) { 76 // no-op 77 } 78 }