content: /**
   *
   * 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 com.alibaba.wasp.zookeeper;
  
  /**
   * Base class for internal listeners of ZooKeeper events.
   * 
   * The {@link ZooKeeperWatcher} for a process will execute the appropriate
   * methods of implementations of this class. In order to receive events from the
   * watcher, every listener must register itself via
   * {@link ZooKeeperWatcher#registerListener}.
   * 
   * Subclasses need only override those methods in which they are interested.
   * 
   * Note that the watcher will be blocked when invoking methods in listeners so
   * they must not be long-running.
   */
  public abstract class ZooKeeperListener {
  
    // Reference to the zk watcher which also contains configuration and constants
    protected ZooKeeperWatcher watcher;
  
    /**
     * Construct a ZooKeeper event listener.
     */
    public ZooKeeperListener(ZooKeeperWatcher watcher) {
      this.watcher = watcher;
    }
  
    /**
     * Called when a new node has been created.
     * @param path full path of the new node
     */
    public void nodeCreated(String path) {
      // no-op
    }
  
    /**
     * Called when a node has been deleted
     * @param path full path of the deleted node
     */
    public void nodeDeleted(String path) {
      // no-op
    }
  
    /**
     * Called when an existing node has changed data.
     * @param path full path of the updated node
     */
    public void nodeDataChanged(String path) {
      // no-op
    }
  
    /**
     * Called when an existing node has a child node added or removed.
     * @param path full path of the node whose children have changed
     */
    public void nodeChildrenChanged(String path) {
      // no-op
    }
  }
  