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. 024 * 025 * The {@link ZKWatcher} for a process will execute the appropriate 026 * methods of implementations of this class. In order to receive events from 027 * the watcher, every listener must register itself via {@link ZKWatcher#registerListener}. 028 * 029 * Subclasses need only override those methods in which they are interested. 030 * 031 * Note that the watcher will be blocked when invoking methods in listeners so 032 * they must not be long-running. 033 */ 034@InterfaceAudience.Private 035public abstract class ZKListener { 036 037 // Reference to the zk watcher which also contains configuration and constants 038 protected ZKWatcher watcher; 039 040 /** 041 * Construct a ZooKeeper event listener. 042 */ 043 public ZKListener(ZKWatcher watcher) { 044 this.watcher = watcher; 045 } 046 047 /** 048 * Called when a new node has been created. 049 * @param path full path of the new node 050 */ 051 public void nodeCreated(String path) { 052 // no-op 053 } 054 055 /** 056 * Called when a node has been deleted 057 * @param path full path of the deleted node 058 */ 059 public void nodeDeleted(String path) { 060 // no-op 061 } 062 063 /** 064 * Called when an existing node has changed data. 065 * @param path full path of the updated node 066 */ 067 public void nodeDataChanged(String path) { 068 // no-op 069 } 070 071 /** 072 * Called when an existing node has a child node added or removed. 073 * @param path full path of the node whose children have changed 074 */ 075 public void nodeChildrenChanged(String path) { 076 // no-op 077 } 078 079 /** 080 * @return The watcher associated with this listener 081 */ 082 public ZKWatcher getWatcher() { 083 return this.watcher; 084 } 085}