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1、pom.xml中添加zookeeper依赖
<dependency> <groupId>org.apache.zookeeper</groupId> <artifactId>zookeeper</artifactId> <version>3.4.6</version> </dependency>
2、DistributedLock.java
package com.zk.dlm;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.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.atomic.AtomicInteger;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
/**
* Created by Administrator on 2015/11/8.
*/
public class DistributedLock implements Lock, Watcher {
private ZooKeeper zk = null;
private String root = "/locks";//根
private String lockName;//竞争资源的标志
private String waitNode;//等待前一个锁
private String myZnode;//当前锁
private CountDownLatch latch;//计数器
private int sessionTimeout = 5000;
private boolean isGetLock = false;
static volatile AtomicInteger count = new AtomicInteger(0);
private DistributedLock(){
}
public static DistributedLock instanceLock(String lockName){
return new DistributedLock(lockName);
}
/**
* 创建分布式锁,使用前请确认config配置的zookeeper服务可用
* @param config 127.0.0.1:2181
* @param lockName 竞争资源标志,lockName中不能包含单词lock
*/
private DistributedLock(String lockName){
this.lockName = lockName;
// 创建一个与服务器的连接
try {
zk = initZk();
Stat stat = zk.exists(root, false);
if(stat == null){
// 创建根节点
zk.create(root, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}
} catch (KeeperException e) {
throw new LockException(e);
} catch (InterruptedException e) {
throw new LockException(e);
}
}
/**
* zookeeper节点的监视器
*/
public void process(WatchedEvent event) {
if(this.latch != null) {
this.latch.countDown();
}
}
public void lock() {
try {
if(this.tryLock()){
//System.out.println("Thread " + Thread.currentThread().getId() + " " +myZnode + " get lock true");
return;
}
else{
waitForLock(waitNode, sessionTimeout);//等待锁
}
} catch (KeeperException e) {
throw new LockException(e);
} catch (InterruptedException e) {
throw new LockException(e);
}
}
public boolean tryLock() {
try {
String splitStr = "_lock_";
if(lockName.contains(splitStr)){
throw new LockException("lockName can not contains \\u000B");
}
//创建临时子节点
myZnode = zk.create(root + "/" + lockName + splitStr, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
//System.out.println(myZnode + " is created ");
//取出所有子节点
List<String> subNodes = zk.getChildren(root, false);
//取出所有lockName的锁
List<String> lockObjNodes = new ArrayList<String>();
for (String node : subNodes) {
String _node = node.split(splitStr)[0];
if(_node.equals(lockName)){
lockObjNodes.add(node);
}
}
Collections.sort(lockObjNodes);
//System.out.println(myZnode + "==" + lockObjNodes.get(0));
if(myZnode.equals(root+"/"+lockObjNodes.get(0))){
//如果是最小的节点,则表示取得锁
return true;
}
//如果不是最小的节点，找到比自己小1的节点
String subMyZnode = myZnode.substring(myZnode.lastIndexOf("/") + 1);
waitNode = lockObjNodes.get(Collections.binarySearch(lockObjNodes, subMyZnode) - 1);
} catch (KeeperException e) {
throw new LockException(e);
} catch (InterruptedException e) {
throw new LockException(e);
}
return false;
}
@SuppressWarnings("finally")
public boolean tryLock(long time, TimeUnit unit) {
try {
if(this.tryLock()){
return true;
}
return waitForLock(waitNode,time);
} catch (Exception e) {
throw new LockException(e);
}finally{
return false;
}
}
private boolean waitForLock(String lower, long waitTime) throws InterruptedException, KeeperException {
Stat stat = zk.exists(root + "/" + lower,true);
//判断比自己小一个数的节点是否存在,如果不存在则无需等待锁,同时注册监听
if(stat != null){
//System.out.println("Thread " + Thread.currentThread().getId() + " waiting for " + root + "/" + lower);
this.latch = new CountDownLatch(1);
isGetLock = this.latch.await(waitTime, TimeUnit.MILLISECONDS);
this.latch = null;
}
return true;
}
public void unlock() {
try {
//System.out.println("unlock " + myZnode);
zk.delete(myZnode,-1);
myZnode = null;
//zk.close();
} catch (InterruptedException e) {
throw new LockException(e);
} catch (KeeperException e) {
throw new LockException(e);
}
}
public synchronized ZooKeeper initZk() {
try {
if(zk==null){
zk = new ZooKeeper("127.0.0.1:2181", sessionTimeout,this);
}
} catch (IOException e) {
throw new LockException("zk init connect fail" + e.getMessage());
//System.err.println("zk init connect fail" + e.getMessage());
}
return zk;
}
public void lockInterruptibly() throws InterruptedException {
this.lock();
}
public Condition newCondition() {
return null;
}
public boolean isGetLock() {
return isGetLock;
}
class LockException extends RuntimeException {
private static final long serialVersionUID = 1L;
public LockException(String e){
super(e);
}
public LockException(Exception e){
super(e);
}
}
public static void main(String[] args) throws Exception {
final long starttime = System.currentTimeMillis();
for(int i=0;i<30;i++){
new Thread(new Runnable() {
public void run() {
DistributedLock lock = DistributedLock.instanceLock("mylock");;
while(true){
try {
lock.lock();
count.incrementAndGet();
System.err.println(System.currentTimeMillis()+"|"+Thread.currentThread().getId() + " | lock value: " + count.get());
} catch (Exception e) {
e.printStackTrace();
}finally{
lock.unlock();
long endtime = System.currentTimeMillis();
System.err.println(count.get()/((endtime-starttime)/1000)+"/s");
}
}
}
}).start();
}
//Thread.sleep(10000);
}
}
参考
caurtor 实现的zk分布式锁
redisson 实现的redis分布式锁
如果规模很大推荐caurtor 如果不是特别大用redisson 就可以
http://www.jiacheo.org/blog/620
http://www.jiacheo.org/blog/122
http://blog.csdn.net/zhu_tianwei/article/details/44927331
https://github.com/mrniko/redisson
http://www.pandablog.cn/41.html
http://blog.csdn.net/zhu_tianwei/article/details/44927331 jedis实现
https://github.com/sfines/menagerie
http://www.111cn.net/jsp/Java/95461.htm
http://itfish.net/article/23060.html
http://www.qkeye.com/blog-37-456727.html
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原文地址：http://my.oschina.net/u/1757031/blog/527811
