ZK（ZooKeeper）分布式锁实现

import org.apache.zookeeper.*;import org.apache.zookeeper.data.Stat;
import java.util.Collections;import java.util.List;import java.util.concurrent.CountDownLatch;

/** * @program: mxnzookeeper * @ClassName WatchCallBack * @description: * @author: 微信搜索：牧小农 * @create: 2021-10-23 10:48 * @Version 1.0 **/public class WatchCallBack  implements Watcher, AsyncCallback.StringCallback ,AsyncCallback.Children2Callback ,AsyncCallback.StatCallback {
    ZooKeeper zk ;    String threadName;    CountDownLatch cc = new CountDownLatch(1);    String pathName;
    public String getPathName() {        return pathName;    }
    public void setPathName(String pathName) {        this.pathName = pathName;    }
    public String getThreadName() {        return threadName;    }
    public void setThreadName(String threadName) {        this.threadName = threadName;    }
    public ZooKeeper getZk() {        return zk;    }
    public void setZk(ZooKeeper zk) {        this.zk = zk;    }
    /** @Author 牧小农     * @Description //TODO 尝试加锁方法     * @Date 16:14 2021/10/24     * @Param      * @return      **/    public void tryLock(){        try {
            System.out.println(threadName + " 开始创建。。。。");            //创建一个顺序临时节点            zk.create("/lock",threadName.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL,this,"abc");            //阻塞当前，监听前一个节点是否释放锁            cc.await();        } catch (InterruptedException e) {            e.printStackTrace();        }    }
    /** @Author 牧小农     * @Description //TODO 解锁方法     * @Date 16:14 2021/10/24     * @Param      * @return      **/    public void unLock(){        try {            //释放锁，删除临时节点            zk.delete(pathName,-1);            //结束工作            System.out.println(threadName + "         结束工作了....");        } catch (InterruptedException e) {            e.printStackTrace();        } catch (KeeperException e) {            e.printStackTrace();        }    }

    @Override    public void process(WatchedEvent event) {
        //如果第一个节点释放了锁，那么第二个就会收到回调        //告诉它前一个节点释放了，你可以开始尝试获取锁        switch (event.getType()) {            case None:                break;            case NodeCreated:                break;            case NodeDeleted:                //当前节点重新获取锁                zk.getChildren("/",false,this ,"sdf");                break;            case NodeDataChanged:                break;            case NodeChildrenChanged:                break;        }
    }
    @Override    public void processResult(int rc, String path, Object ctx, String name) {        if(name != null ){            System.out.println(threadName  +" 线程创建了一个节点为 : " +  name );            pathName =  name ;            //监听前一个节点            zk.getChildren("/",false,this ,"sdf");        }
    }
    //getChildren  call back    @Override    public void processResult(int rc, String path, Object ctx, List<String> children, Stat stat) {
        //节点按照编号，升序排列        Collections.sort(children);        //对节点进行截取例如  /lock0000000022 截取后就是  lock0000000022        int i = children.indexOf(pathName.substring(1));

        //是不是第一个，也就是说是不是最小的        if(i == 0){            //是第一个            System.out.println(threadName +" 现在我是最小的....");            try {                zk.setData("/",threadName.getBytes(),-1);                cc.countDown();
            } catch (KeeperException e) {                e.printStackTrace();            } catch (InterruptedException e) {                e.printStackTrace();            }        }else{            //不是第一个            //监听前一个节点 看它是不是完成了工作进行释放锁了            zk.exists("/"+children.get(i-1),this,this,"sdf");        }
    }
    @Override    public void processResult(int rc, String path, Object ctx, Stat stat) {        //判断是否失败exists    }}

import com.mxn.zookeeper.config.ZKUtils;import org.apache.zookeeper.ZooKeeper;import org.junit.After;import org.junit.Before;import org.junit.Test;

/** * @program: mxnzookeeper * @ClassName TestLock * @description: * @author: 微信搜索：牧小农 * @create: 2021-10-23 10:45 * @Version 1.0 **/public class TestLock {

    ZooKeeper zk ;
    @Before    public void conn (){        zk  = ZKUtils.getZK();    }
    @After    public void close (){        try {            zk.close();        } catch (InterruptedException e) {            e.printStackTrace();        }    }
    @Test    public void lock(){
        //创建十个线程        for (int i = 0; i < 10; i++) {            new Thread(){                @Override                public void run() {                    WatchCallBack watchCallBack = new WatchCallBack();                    watchCallBack.setZk(zk);                    String threadName = Thread.currentThread().getName();                    watchCallBack.setThreadName(threadName);                    //线程进行抢锁操作                    watchCallBack.tryLock();                    try {                        //进行业务逻辑处理                        System.out.println(threadName+"         开始处理业务逻辑了...");                        Thread.sleep(200);                    }catch (Exception e){                        e.printStackTrace();                    }                    //释放锁                    watchCallBack.unLock();

                }            }.start();        }

        while(true){
        }
    }
}

Thread-1 线程创建了一个节点为 : /lock0000000112Thread-5 线程创建了一个节点为 : /lock0000000113Thread-2 线程创建了一个节点为 : /lock0000000114Thread-6 线程创建了一个节点为 : /lock0000000115Thread-9 线程创建了一个节点为 : /lock0000000116Thread-4 线程创建了一个节点为 : /lock0000000117Thread-7 线程创建了一个节点为 : /lock0000000118Thread-3 线程创建了一个节点为 : /lock0000000119Thread-8 线程创建了一个节点为 : /lock0000000120Thread-0 线程创建了一个节点为 : /lock0000000121Thread-1 现在我是最小的....Thread-1         开始处理业务逻辑了...Thread-1         结束工作了....Thread-5 现在我是最小的....Thread-5         开始处理业务逻辑了...Thread-5         结束工作了....Thread-2 现在我是最小的....Thread-2         开始处理业务逻辑了...Thread-2         结束工作了....Thread-6 现在我是最小的....Thread-6         开始处理业务逻辑了...Thread-6         结束工作了....Thread-9 现在我是最小的....Thread-9         开始处理业务逻辑了...Thread-9         结束工作了....Thread-4 现在我是最小的....Thread-4         开始处理业务逻辑了...Thread-4         结束工作了....Thread-7 现在我是最小的....Thread-7         开始处理业务逻辑了...Thread-7         结束工作了....Thread-3 现在我是最小的....Thread-3         开始处理业务逻辑了...Thread-3         结束工作了....Thread-8 现在我是最小的....Thread-8         开始处理业务逻辑了...Thread-8         结束工作了....Thread-0 现在我是最小的....Thread-0         开始处理业务逻辑了...Thread-0         结束工作了....