1 /** 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 */ 19 package org.apache.hadoop.hbase.zookeeper; 20 21 import org.apache.hadoop.classification.InterfaceAudience; 22 import org.apache.hadoop.classification.InterfaceStability; 23 24 25 /** 26 * Base class for internal listeners of ZooKeeper events. 27 * 28 * The {@link ZooKeeperWatcher} for a process will execute the appropriate 29 * methods of implementations of this class. In order to receive events from 30 * the watcher, every listener must register itself via {@link ZooKeeperWatcher#registerListener}. 31 * 32 * Subclasses need only override those methods in which they are interested. 33 * 34 * Note that the watcher will be blocked when invoking methods in listeners so 35 * they must not be long-running. 36 */ 37 @InterfaceAudience.Public 38 @InterfaceStability.Evolving 39 public abstract class ZooKeeperListener { 40 41 // Reference to the zk watcher which also contains configuration and constants 42 protected ZooKeeperWatcher watcher; 43 44 /** 45 * Construct a ZooKeeper event listener. 46 */ 47 public ZooKeeperListener(ZooKeeperWatcher watcher) { 48 this.watcher = watcher; 49 } 50 51 /** 52 * Called when a new node has been created. 53 * @param path full path of the new node 54 */ 55 public void nodeCreated(String path) { 56 // no-op 57 } 58 59 /** 60 * Called when a node has been deleted 61 * @param path full path of the deleted node 62 */ 63 public void nodeDeleted(String path) { 64 // no-op 65 } 66 67 /** 68 * Called when an existing node has changed data. 69 * @param path full path of the updated node 70 */ 71 public void nodeDataChanged(String path) { 72 // no-op 73 } 74 75 /** 76 * Called when an existing node has a child node added or removed. 77 * @param path full path of the node whose children have changed 78 */ 79 public void nodeChildrenChanged(String path) { 80 // no-op 81 } 82 }