zookeeper java的API 入门使用

一.创建简单的maven项目导包

<dependency>
  <groupId>org.apache.zookeeper</groupId>
  <artifactId>zookeeper</artifactId>
  <version>3.6.3</version>
</dependency>

二.编辑 代码

package com.wqj;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.util.concurrent.CountDownLatch;
  //Hello world!
public class App {
    //连接字符串。zk server zkConnectString地址和端口
    private static String zkConnectString ="192.168.0.133:2181,192.168.0.134:2181,192.168.0.135:2181";
    // 会话超时时间 单位ms
    private static int sessionTimeout =3000;
    //监视器对象
    public static void main( String[] args ) throws Exception {
        System.out.println( "Hello World!" );
        //1.创建zk对象
        /* //zk有session的概念，没有连接池的概念
        //watch: 观察回调,回调。
        //watch的注册值发生在 读类型调用
        //第一类：new zk 时候，传入的watch，这个watch，session级别的，跟path 、node没有关系
            ZooKeeper(String connectString, int sessionTimeout, Watcher watcher)
            第一个参数： zookeeper服务器的地址
            第二个参数： 超时时间一般为心跳时间的2倍
            第三个参数： 该对象用来处理zookeeper服务器响应的事件
         */
        //加锁同步执行
        final CountDownLatch countDownLatch = new CountDownLatch(1);
        final ZooKeeper zk = new ZooKeeper(zkConnectString, sessionTimeout, new Watcher() {
            //默认watcher
            /*
             * 回调函数：
             * 当我们需要监听的事件发生以后，那么zookeeper服务器就会调用该方法。
             * 当前这个构造器中的该对象是用来响应所有的事件。
             * */
          @Override
            public void process(WatchedEvent event) {
                //获取数据KeeperStatus通知状态
                Event.KeeperState state = event.getState();
                //获取EventType事件类型
                Event.EventType type = event.getType();
                //获取地址
              String path = event.getPath();
              System.out.println("new zk path(创建 zk 连接获取地址：) " +path);
              //判断数据类型  KeeperStatus通知状态
              //switch (state) + 快捷键 Alt +enter
              switch (state) {
                  case Unknown:
                      break;
                  case Disconnected:
                      break;
                  case NoSyncConnected:
                      break;
                  case SyncConnected:
                      System.out.println("connected(连接创建成功):");
                      countDownLatch.countDown();
                      break;
                  case AuthFailed:
                      break;
                  case ConnectedReadOnly:
                      break;
                  case SaslAuthenticated:
                      break;
                  case Expired:
                      break;
                  case Closed:
                      break;
              }

              switch (type) {
                  case None:
                      break;
                  case NodeCreated:
                      break;
                  case NodeDeleted:
                      break;
                  case NodeDataChanged:
                      break;
                  case NodeChildrenChanged:
                      break;
                  case DataWatchRemoved:
                      break;
                  case ChildWatchRemoved:
                      break;
                  case PersistentWatchRemoved:
                      break;
              }

          }

        });
        countDownLatch.await();
        final ZooKeeper.States state = zk.getState();
        switch (state) {
            case CONNECTING:
                System.out.println("CONNECTING---------------");
                break;
            case ASSOCIATING:
                System.out.println("ASSOCIATING------------");
                break;
            case CONNECTED:
                break;
            case CONNECTEDREADONLY:
                break;
            case CLOSED:
                break;
            case AUTH_FAILED:
                break;
            case NOT_CONNECTED:
                break;
        }
/***
 *    final String path,
 *         byte[] data,
 *         List<ACL> acl, 权限
 *                    OPEN_ACL_UNSAFE  : 完全开放的ACL，任何连接的客户端都可以操作该属性znode
 *                    CREATOR_ALL_ACL : 只有创建者才有ACL权限
 *                    READ_ACL_UNSAFE：只能读取ACL
 *         CreateMode createMode 节点类型  临时
 */
        String pathName = zk.create("/wqj", "wqj_wqj".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);


        final Stat stat = new Stat();
        byte[] node = zk.getData("/wqj", new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                System.out.println("getData watch:--------------"+event.toString());
              //  System.out.println("没有回调----");
                try {
                    zk.getData("/wqj",this,stat);
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },stat);
        System.out.println("node---"+new String(node));
                /** 触发回调
                 * final String path,
                 * byte[] data,
                 * int version  版本 ，每一次不同
                 */
      Stat stat01 = zk.setData("/wqj", "wqj_0112".getBytes(), 0);
        //还会回调吗？ 还会的
     Stat stat02 = zk.setData("/wqj", "wqj_011".getBytes(), stat01.getVersion());
        System.out.println("-------async start----------");
        zk.getData("/wqj", false, new AsyncCallback.DataCallback() {
            @Override
            public void processResult(int rc, String path, Object ctx, byte[] data, Stat stat) {
                System.out.println("-------async call back----------");
                System.out.println(ctx.toString());
                System.out.println(new String(data));

            }

        },"wqjj");
        System.out.println("-------async over----------");

        Thread.sleep(2222);
    }
}