CuratorFramework节点监听一 PathChildrenCache

节点监听

一. PathChildrenCache

特点：

（1）永久监听指定节点下的节点
（2）只能监听指定节点下一级节点的变化，比如说指定节点”/example”, 在下面添加”node1”可以监听到，但是添加”node1/n1”就不能被监听到了
（3）可以监听到的事件：节点创建、节点数据的变化、节点删除等

使用方式

（1）创建curatorframework的client
（2）添加PathChildrenCache
（3）启动client 和 pathChildrenCache
（4）注册监听器

例子：

package cache;

import com.google.common.collect.Lists;
import discovery.ExampleServer;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.*;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.utils.ZKPaths;
import org.apache.zookeeper.KeeperException;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.List;

/**
 * An example of the PathChildrenCache. The example "harness" is a command processor
 * that allows adding/updating/removed nodes in a path. A PathChildrenCache keeps a
 * cache of these changes and outputs when updates occurs.
 */
public class PathCacheExample {
   
    private static final String PATH = "/mq_monitor";
    static CuratorFramework client = CuratorFrameworkFactory.newClient("192.168.27.55", new ExponentialBackoffRetry(1000, 3));
    static PathChildrenCache pathChildrenCache = new PathChildrenCache(client, PATH, true);
    public static void main(String[] args) throws Exception {
        start();
    }

    public static void start() {
        try {
            client.start();
            pathChildrenCache.start();
            addPathChildListener(pathChildrenCache);
            processCommands(client, pathChildrenCache);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void shutdown() {
        CloseableUtils.closeQuietly(pathChildrenCache);
        CloseableUtils.closeQuietly(client);
    }

    private static void addPathChildListener(PathChildrenCache cache) {
        // a PathChildrenCacheListener is optional. Here, it's used just to log changes
        PathChildrenCacheListener listener = new PathChildrenCacheListener() {
            @Override
            public void