import org.apache.zookeeper.*;

import java.util.List;

public class Main {
    public static void main(String[] args) {
        //初始化log4j，zookeeper否则报错。
        org.apache.log4j.BasicConfigurator.configure();

        try {
            Main m = new Main("");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public Main(String arg){
        try {
            test();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private ZooKeeper mZooKeeper;

    private void test() throws Exception{
        String ip = "localhost";
        String addrs = ip + ":2181," + ip + ":2182," + ip + ":2183";

        //连接zookeeper服务器。
        //addrs是一批地址，如果其中某一个服务器挂掉，其他仍可用。
        mZooKeeper = new ZooKeeper(addrs, 300 * 1000, new MyWatcher());

        synchronized (Main.class) {
            System.out.println("处理...");
            Main.class.wait();
        }
    }

    private class MyWatcher implements Watcher {
        @Override
        public void process(WatchedEvent event) {
            byte[] data =null;
            try {
                data = mZooKeeper.getData("/test_data", true, null);
            } catch (Exception e) {
                e.printStackTrace();
            }

            System.out.println("类型:" + event.getType());
            System.out.println("路径:" + event.getPath());
            if(data!=null)
            System.out.println("数据修改:" + new String(data));

            if (mZooKeeper.getState() == ZooKeeper.States.CONNECTED) {
                System.out.println("状态:ZooKeeper.States.CONNECTED");
            }

            if (event.getState() == Event.KeeperState.SyncConnected) {
                System.out.println("状态:Event.KeeperState.SyncConnected");
            }
        }
    }
}

此时，若在监听的节点/test_data通过set命令更新数据

Java程序代码输出：

类型:NodeDataChanged
路径:/test_data
数据修改:hello.world!
状态:ZooKeeper.States.CONNECTED