ZooKeeper(3.4.5) - 使用 Curator(2.7.0) 监听事件

ZooKeeper原生的API支持通过注册Watcher来进行事件监听，但是Watcher通知是一次性的，因此开发过程中需要反复注册Watcher，比较繁琐。Curator引入了Cache来监听ZooKeeper服务端的事件。Cache对ZooKeeper事件监听进行了封装，能够自动处理反复注册监听，简化了ZooKeeper原生API繁琐的开发过程。

 

简单的示例：

package com.huey.dream.demo;



import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;



import org.apache.curator.framework.CuratorFramework;

import org.apache.curator.framework.CuratorFrameworkFactory;

import org.apache.curator.framework.recipes.cache.NodeCache;

import org.apache.curator.framework.recipes.cache.NodeCacheListener;

import org.apache.curator.framework.recipes.cache.PathChildrenCache;

import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;

import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;

import org.apache.curator.framework.recipes.cache.PathChildrenCache.StartMode;

import org.apache.curator.retry.ExponentialBackoffRetry;



/**

 * Curator事件监听

 * @author  huey

 * @version 1.0 

 * @created 2015-3-2

 */

public class CarutorDemo {



    public static void main(String[] args) throws Exception {

        CuratorFramework client = CuratorFrameworkFactory.builder()

            .connectString("192.168.1.109:2181")

            .sessionTimeoutMs(5000)

            .connectionTimeoutMs(3000)

            .retryPolicy(new ExponentialBackoffRetry(1000, 3))

            .build();

        client.start();

        

        client.create()

            .creatingParentsIfNeeded()

            .forPath("/zk-huey/cnode", "hello".getBytes());

        

        /**

         * 在注册监听器的时候，如果传入此参数，当事件触发时，逻辑由线程池处理

         */

        ExecutorService pool = Executors.newFixedThreadPool(2);

        

        /**

         * 监听数据节点的变化情况

         */

        final NodeCache nodeCache = new NodeCache(client, "/zk-huey/cnode", false);

        nodeCache.start(true);

        nodeCache.getListenable().addListener(

            new NodeCacheListener() {

                @Override

                public void nodeChanged() throws Exception {

                    System.out.println("Node data is changed, new data: " + 

                        new String(nodeCache.getCurrentData().getData()));

                }

            }, 

            pool

        );

        

        /**

         * 监听子节点的变化情况

         */

        final PathChildrenCache childrenCache = new PathChildrenCache(client, "/zk-huey", true);

        childrenCache.start(StartMode.POST_INITIALIZED_EVENT);

        childrenCache.getListenable().addListener(

            new PathChildrenCacheListener() {

                @Override

                public void childEvent(CuratorFramework client, PathChildrenCacheEvent event)

                        throws Exception {

                        switch (event.getType()) {

                        case CHILD_ADDED:

                            System.out.println("CHILD_ADDED: " + event.getData().getPath());

                            break;

                        case CHILD_REMOVED:

                            System.out.println("CHILD_REMOVED: " + event.getData().getPath());

                            break;

                        case CHILD_UPDATED:

                            System.out.println("CHILD_UPDATED: " + event.getData().getPath());

                            break;

                        default:

                            break;

                    }

                }

            },

            pool

        );

        

        client.setData().forPath("/zk-huey/cnode", "world".getBytes());

        

        Thread.sleep(10 * 1000);

        pool.shutdown();

        client.close();

    }

}