zookeeper分布式锁实现秒杀案例（jfinal框架）ZooKeeper是一个分布式的，开放源码的分布式应用程序协调服务，是Google的Chubby一个开源的实现，是Hadoop和Hbase的重要组件。它是一个为分布式应用提供一致性服务的软件，提供的功能包括：配置维护、域名服务、分布式同步、组服务等。ZooKeeper的架构通过冗余服务实现高可用性。因此，如果第一次无应答，客户端就可以询问另一台ZooKeeper主机。ZooKeeper节点将它们的数据存储于一个分层的命名空间，非常类似于一个文件系统或一个前缀树结构。客户端可以在节点读写，从而以这种方式拥有一个共享的配置服务。更新是全序的。基于ZooKeeper分布式锁的流程在zookeeper指定节点（locks）下创建临时顺序节点node_n获取locks下所有子节点children对子节点按节点自增序号从小到大排序判断本节点是不是第一个子节点，若是，则获取锁；若不是，则监听比该节点小的那个节点的删除事件若监听事件生效，则回到第二步重新进行判断，直到获取到锁具体实现下面就具体使用java和zookeeper实现分布式锁，操作zookeeper使用的是apache提供的zookeeper的包。通过实现Watch接口，实现process(WatchedEvent event)方法来实施监控，使CountDownLatch来完成监控，在等待锁的时候使用CountDownLatch来计数，等到后进行countDown，停止等待，继续运行。以下整体流程基本与上述描述流程一致，只是在监听的时候使用的是CountDownLatch来监听前一个节点。下边来看简单的实现源码，不用在乎代码的质量，这里只是简单地做个演示！！！分布式锁：package com.demo.utils;import org.apache.zookeeper.;import org.apache.zookeeper.data.Stat; import java.io.IOException;import java.util.ArrayList;import java.util.Collections;import java.util.List;import java.util.concurrent.CountDownLatch;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock; public class DistributedLock implements Lock, Watcher {private ZooKeeper zk = null; // 根节点 private String ROOT_LOCK = "/locks"; // 竞争的资源 private String lockName;// 等待的前一个锁private String WAIT_LOCK;// 当前锁public String CURRENT_LOCK;// 计数器private CountDownLatch countDownLatch;private int sessionTimeout = 30000;private List<Exception> exceptionList = new ArrayList<Exception>(); / 配置分布式锁 @param config 连接的url @param lockName 竞争资源*/public DistributedLock(String config, String lockName) {this.lockName = lockName; try { // 连接zookeeper zk = new ZooKeeper(config, sessionTimeout, this); Stat stat = zk.exists(ROOT_LOCK, false);if (stat == null) {// 如果根节点不存在，则创建根节点zk.create(ROOT_LOCK, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);}} catch (IOException e) {// e.printStackTrace();} catch (InterruptedException e) {// e.printStackTrace();} catch (KeeperException e) {// e.printStackTrace();}} // 节点监视器public void process(WatchedEvent event) {if (this.countDownLatch != null) {this.countDownLatch.countDown();}} public void lock() {if (exceptionList.size() > 0) {throw new LockException(exceptionList.get(0));}try {if (this.tryLock()) {// System.out.println(Thread.currentThread().getName() + " " + lockName + “获得了锁”);return;} else {// 等待锁waitForLock(WAIT_LOCK, sessionTimeout);} } catch (InterruptedException e) {e.printStackTrace();} catch (KeeperException e) { e.printStackTrace();}} public boolean tryLock() {try {String splitStr = "lock";if (lockName.contains(splitStr)) { throw new LockException(“锁名有误”); }// 创建临时有序节点CURRENT_LOCK = zk.create(ROOT_LOCK + "/" + lockName + splitStr, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); // System.out.println(CURRENT_LOCK + " 已经创建");// 取所有子节点List<String> subNodes = zk.getChildren(ROOT_LOCK, false);// 取出所有lockName的锁List<String> lockObjects = new ArrayList<String>();for (String node : subNodes) {String _node = node.split(splitStr)[0];if (_node.equals(lockName)) {lockObjects.add(node);}}Collections.sort(lockObjects);// System.out.println(Thread.currentThread().getName() + " 的锁是 " + CURRENT_LOCK);// 若当前节点为最小节点，则获取锁成功if (CURRENT_LOCK.equals(ROOT_LOCK + "/" + lockObjects.get(0))) {return true;} // 若不是最小节点，则找到自己的前一个节点String prevNode = CURRENT_LOCK.substring(CURRENT_LOCK.lastIndexOf("/") + 1);WAIT_LOCK = lockObjects.get(Collections.binarySearch(lockObjects, prevNode) - 1); } catch (InterruptedException e) {e.printStackTrace();} catch (KeeperException e) {e.printStackTrace();} return false; } public boolean tryLock(long timeout, TimeUnit unit) {try { if (this.tryLock()) { return true;}return waitForLock(WAIT_LOCK, timeout);} catch (Exception e) {e.printStackTrace();}return false; } // 等待锁 private boolean waitForLock(String prev, long waitTime) throws KeeperException, InterruptedException {Stat stat = zk.exists(ROOT_LOCK + "/" + prev, true); if (stat != null) {// System.out.println(Thread.currentThread().getName() + “等待锁 " + ROOT_LOCK + ”/" + prev); this.countDownLatch = new CountDownLatch(1); // 计数等待，若等到前一个节点消失，则precess中进行countDown，停止等待，获取锁 this.countDownLatch.await(waitTime, TimeUnit.MILLISECONDS); this.countDownLatch = null; // System.out.println(Thread.currentThread().getName() + " 等到了锁"); } return true;} public void unlock() {try { System.out.println(“释放锁 " + CURRENT_LOCK);zk.delete(CURRENT_LOCK, -1);CURRENT_LOCK = null;zk.close();} catch (InterruptedException e) {e.printStackTrace();} catch (KeeperException e) {e.printStackTrace();}} public Condition newCondition() {return null;} public void lockInterruptibly() throws InterruptedException {this.lock();} public class LockException extends RuntimeException {private static final long serialVersionUID = 1L;public LockException(String e){super(e);}public LockException(Exception e){super(e);}}}