基于zookeeper实现分布式锁

1、添加zookeeper依赖

    
      org.apache.zookeeper
      zookeeper
      3.4.13
    

2、代码部分：

package com.imooc.lock;

import org.apache.zookeeper.*;

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

/**
 * @Author: dahai.li
 * @Description: 基于zk实现分布式锁
 * @Date: Create in 16:51 2019/8/27
 */
public class ZkLock {

    private ZooKeeper zooKeeper;
    private static CountDownLatch countDownLatch = new CountDownLatch(1);

    private ZkLock() {
        try {
            zooKeeper = new ZooKeeper("192.1.1.101:2181,192.1.1.102:2181,192.1.1.103:2181",5000,new ZkWatcher(){});
            System.out.println(zooKeeper.getState());
            try {
                countDownLatch.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    public static ZkLock getInstance(){
        return Singleton.getInstance();
    }


    private class ZkWatcher implements Watcher {
        @Override
        public void process(WatchedEvent event) {
            System.out.println("接收到监听事件===》"+event);
            if (Event.KeeperState.SyncConnected == event.getState()) {
                countDownLatch.countDown();
            }
        }
    }


    /**
     * 获取锁
     * @param id
     */
    public void lock(Integer id) {
        String path = "/xdclass-product-lock-" + id;
        //创建临时节点,如果创建成功，就表示获取锁，如果失败则不断重试
        try {
            zooKeeper.create(path, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        } catch (Exception e) {
            while (true){
                try {
                    Thread.sleep(500L);
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
                try {
                    zooKeeper.create(path, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
                } catch (Exception e1) {
                    continue;
                }
                break;
            }
        }
    }

    /**
     * 释放锁
     * @param id
     */
    public void unLock(Integer id) {
        String path = "/xdclass-product-lock-" + id;
        try {
            zooKeeper.delete(path, -1);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static class Singleton {

        private static ZkLock instance;
        static {
            instance = new ZkLock();
        }

        private static ZkLock getInstance(){
            return instance;
        }
    }
}

 

3、几个注意点：

  (1) 原生api不支持递归创建节点

  (2) 如果是单一应用，尽量不要使用分布式锁（可以使用原生的JDK锁，分布式锁消耗性能）