1.原生Zookeeper 实现分布式锁案例

（1）分布式锁实现

package com.yingzi.zkcase2;import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;/*** @author 影子* @create 2022-01-18-15:49**/
public class DistributedLock {// zookeeper server 列表private String connectString ="hadoop102:2181,hadoop103:2181,hadoop104:2181";// 超时时间private int sessionTimeout = 2000;private ZooKeeper zk;private String rootNode = "locks";private String subNode = "seq-";// 当前 client 等待的子节点private String waitPath;//ZooKeeper 连接private CountDownLatch connectLatch = new CountDownLatch(1);//ZooKeeper 节点等待private CountDownLatch waitLatch = new CountDownLatch(1);// 当前 client 创建的子节点private String currentNode;// 和 zk 服务建立连接，并创建根节点public DistributedLock() throws IOException,InterruptedException, KeeperException {zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {@Overridepublic void process(WatchedEvent event) {// 连接建立时, 打开 latch, 唤醒 wait 在该 latch 上的线程if (event.getState() ==Event.KeeperState.SyncConnected) {connectLatch.countDown();}// 发生了 waitPath 的删除事件if (event.getType() ==Event.EventType.NodeDeleted && event.getPath().equals(waitPath)) {waitLatch.countDown();}}});// 等待连接建立connectLatch.await();//获取根节点状态Stat stat = zk.exists("/" + rootNode, false);//如果根节点不存在，则创建根节点，根节点类型为永久节点if (stat == null) {System.out.println("根节点不存在");zk.create("/" + rootNode, new byte[0],ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);}}// 加锁方法public void zkLock() {try {//在根节点下创建临时顺序节点，返回值为创建的节点路径currentNode = zk.create("/" + rootNode + "/" + subNode,null, ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);// wait 一小会, 让结果更清晰一些Thread.sleep(10);// 注意, 没有必要监听"/locks"的子节点的变化情况List<String> childrenNodes = zk.getChildren("/" +rootNode, false);// 列表中只有一个子节点, 那肯定就是 currentNode , 说明client 获得锁if (childrenNodes.size() == 1) {return;} else {//对根节点下的所有临时顺序节点进行从小到大排序Collections.sort(childrenNodes);//当前节点名称String thisNode = currentNode.substring(("/" +rootNode + "/").length());//获取当前节点的位置int index = childrenNodes.indexOf(thisNode);if (index == -1) {System.out.println("数据异常");} else if (index == 0) {// index == 0, 说明 thisNode 在列表中最小, 当前client 获得锁return;} else {// 获得排名比 currentNode 前 1 位的节点this.waitPath = "/" + rootNode + "/" +childrenNodes.get(index - 1);// 在 waitPath 上注册监听器, 当 waitPath 被删除时,zookeeper 会回调监听器的 process 方法zk.getData(waitPath, true, new Stat());//进入等待锁状态waitLatch.await();return;}}} catch (KeeperException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}}// 解锁方法public void zkUnlock() {try {zk.delete(this.currentNode, -1);} catch (InterruptedException | KeeperException e) {e.printStackTrace();}}
}

（2）测试

package com.yingzi.zkcase2;import org.apache.zookeeper.KeeperException;import java.io.IOException;/*** @author 影子* @create 2022-01-18-16:34**/
public class DistributedLockTest {public static void main(String[] args) throwsInterruptedException, IOException, KeeperException {// 创建分布式锁 1final DistributedLock lock1 = new DistributedLock();// 创建分布式锁 2final DistributedLock lock2 = new DistributedLock();new Thread(new Runnable() {@Overridepublic void run() {// 获取锁对象try {lock1.zkLock();System.out.println("线程 1 获取锁");Thread.sleep(5 * 1000);lock1.zkUnlock();System.out.println("线程 1 释放锁");} catch (Exception e) {e.printStackTrace();}}}).start();new Thread(new Runnable() {@Overridepublic void run() {// 获取锁对象try {lock2.zkLock();System.out.println("线程 2 获取锁");Thread.sleep(5 * 1000);lock2.zkUnlock();System.out.println("线程 2 释放锁");} catch (Exception e) {e.printStackTrace();}}}).start();}
}

2 Curator框架实现分布式锁案例

（1）pom.xml添加依赖

<dependency><groupId>org.apache.curator</groupId><artifactId>curator-framework</artifactId><version>4.3.0</version>
</dependency>
<dependency><groupId>org.apache.curator</groupId><artifactId>curator-recipes</artifactId><version>4.3.0</version>
</dependency>
<dependency><groupId>org.apache.curator</groupId><artifactId>curator-client</artifactId><version>4.3.0</version>
</dependency>

（2）代码实现

package com.yingzi.case3;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.ExponentialBackoffRetry;/*** @author 影子* @create 2022-01-18-16:44**/
public class CuratorLockTest {public static void main(String[] args) {//创建分布式锁1InterProcessMutex lock1 = new InterProcessMutex(getCuratorFramework(), "/locks");//创建分布式锁2InterProcessMutex lock2 = new InterProcessMutex(getCuratorFramework(), "/locks");new Thread(new Runnable() {@Overridepublic void run() {try {lock1.acquire();System.out.println("线程1 获取到锁");lock1.acquire();System.out.println("线程1 再次获取到锁");Thread.sleep(5 * 1000);lock1.release();System.out.println("线程1 释放锁");lock1.release();System.out.println("线程1 再次释放锁");} catch (Exception e) {e.printStackTrace();}}}).start();new Thread(new Runnable() {@Overridepublic void run() {try {lock2.acquire();System.out.println("线程2 获取到锁");lock2.acquire();System.out.println("线程2 再次获取到锁");Thread.sleep(5 * 1000);lock2.release();System.out.println("线程2 释放锁");lock2.release();System.out.println("线程2 再次释放锁");} catch (Exception e) {e.printStackTrace();}}}).start();}private static CuratorFramework getCuratorFramework() {ExponentialBackoffRetry policy = new ExponentialBackoffRetry(3000, 3);CuratorFramework client = CuratorFrameworkFactory.builder().connectString("hadoop102:2181,hadoop103:2181,hadoop104:2181").connectionTimeoutMs(2000).sessionTimeoutMs(2000).retryPolicy(policy).build();//启动客户端client.start();System.out.println("zookeeper 启动成功");return client;}}