中间件 ZK分布式专题与Dubbo微服务入门 6-10 判断zk节点是否存在

0　　　　课程地址

https://coding.imooc.com/lesson/201.html#mid=12726

 

1　　　　重点关注

1.1　　　　本节内容

判断zk节点是否存在demo

 

1.2　　　　关键代码

        /**
         * 参数：
         * path：节点路径
         * watch：watch事件
         */
        Stat stat = zkServer.getZookeeper().exists("/imooc-fake", true);
        if (stat != null) {
            System.out.println("查询的节点版本为dataVersion：" + stat.getVersion());
        } else {
            System.out.println("该节点不存在...");
        }
        

 

//本类watch事件，process，本类实现watcher
public Stat exists(String path, boolean watch)；

//其他类watch事件，process。其他类实现Watcher
public Stat exists(final String path, Watcher watcher)

//本类watch事件，process，本类实现watcher，回调函数
 public void exists(String path, boolean watch, StatCallback cb, Object ctx)；


//其他类watch事件，process。其他类实现Watcher,回调函数
public void exists(final String path, Watcher watcher,
            StatCallback cb, Object ctx);

 

 

 

2　　　　课程内容

 

 

 

3　　　　Coding

3.1　　　　判断zk节点是否存在

• 启动服务端

    进入到
cd /usr/local/zookeeper/bin

 
    重启zookeeper服务端
./zkServer.sh restart

 

• 主类

package com.imooc.zk.demo;

import java.io.IOException;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

/**
 * @Description: zookeeper 判断阶段是否存在demo
 */
public class ZKNodeExist implements Watcher {

    private ZooKeeper zookeeper = null;
    
    public static final String zkServerPath = "172.26.139.4:2181";
    public static final Integer timeout = 5000;
    
    public ZKNodeExist() {}
    
    public ZKNodeExist(String connectString) {
        try {
            zookeeper = new ZooKeeper(connectString, timeout, new ZKNodeExist());
        } catch (IOException e) {
            e.printStackTrace();
            if (zookeeper != null) {
                try {
                    zookeeper.close();
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
            }
        }
    }
    
    private static CountDownLatch countDown = new CountDownLatch(1);
    
    public static void main(String[] args) throws Exception {
    
        ZKNodeExist zkServer = new ZKNodeExist(zkServerPath);
        
        /**
         * 参数：
         * path：节点路径
         * watch：watch
         */
        Stat stat = zkServer.getZookeeper().exists("/imooc-fake", true);
        if (stat != null) {
            System.out.println("查询的节点版本为dataVersion：" + stat.getVersion());
        } else {
            System.out.println("该节点不存在...");
        }
        
        countDown.await();
    }
    
    @Override
    public void process(WatchedEvent event) {
        if (event.getType() == EventType.NodeCreated) {
            System.out.println("节点创建");
            countDown.countDown();
        } else if (event.getType() == EventType.NodeDataChanged) {
            System.out.println("节点数据改变");
            countDown.countDown();
        } else if (event.getType() == EventType.NodeDeleted) {
            System.out.println("节点删除");
            countDown.countDown();
        }
    }
    
    public ZooKeeper getZookeeper() {
        return zookeeper;
    }
    public void setZookeeper(ZooKeeper zookeeper) {
        this.zookeeper = zookeeper;
    }
}

• 打印日志1（暂停状态，等待创建节点）

该节点不存在...

 

• linux客户端创建节点

--启动客户端
zkCli.sh

[zk: localhost:2181(CONNECTED) 0] ls /
[imooc2, names, zookeeper, imooc3, imooc, testnode, imooc5]

[zk: localhost:2181(CONNECTED) 1] create /imooc-fake 555
Created /imooc-fake
[zk: localhost:2181(CONNECTED) 2] 

 

• 打印日志2

该节点不存在...

节点创建