使用Java实现分布式锁

使用Java实现分布式锁

大家好，我是微赚淘客系统3.0的小编，是个冬天不穿秋裤，天冷也要风度的程序猿！在这篇文章中，我将详细介绍如何使用Java实现分布式锁，并结合实际代码示例，帮助大家更好地理解和应用分布式锁技术。

1. 什么是分布式锁

分布式锁是一种用于在分布式系统中控制对共享资源的访问的机制。在分布式环境中，多个进程可能需要同时访问某个共享资源，分布式锁可以确保在任何时刻只有一个进程能够访问该资源，从而避免数据竞争和不一致性问题。

2. 分布式锁的实现方式

分布式锁有多种实现方式，包括基于数据库的分布式锁、基于Redis的分布式锁、基于Zookeeper的分布式锁等。本文将重点介绍如何使用Redis实现分布式锁。

3. 使用Redis实现分布式锁

Redis是一种高性能的键值存储系统，非常适合用来实现分布式锁。我们可以利用Redis的原子操作来实现分布式锁。以下是一个基于Redis的分布式锁的实现示例：

3.1 引入依赖

首先，我们需要在项目中引入Jedis库来操作Redis。在pom.xml中添加以下依赖：

<dependency><groupId>redis.clients</groupId><artifactId>jedis</artifactId><version>4.0.1</version>
</dependency>

3.2 分布式锁的实现

接下来，我们实现一个简单的分布式锁工具类：

package cn.juwatech.lock;import redis.clients.jedis.Jedis;public class RedisDistributedLock {private Jedis jedis;private String lockKey;private int expireTime;public RedisDistributedLock(Jedis jedis, String lockKey, int expireTime) {this.jedis = jedis;this.lockKey = lockKey;this.expireTime = expireTime;}public boolean lock() {long result = jedis.setnx(lockKey, String.valueOf(System.currentTimeMillis() + expireTime));if (result == 1) {jedis.expire(lockKey, expireTime);return true;} else {String currentValue = jedis.get(lockKey);if (currentValue != null && Long.parseLong(currentValue) < System.currentTimeMillis()) {String oldValue = jedis.getSet(lockKey, String.valueOf(System.currentTimeMillis() + expireTime));if (oldValue != null && oldValue.equals(currentValue)) {jedis.expire(lockKey, expireTime);return true;}}}return false;}public void unlock() {String currentValue = jedis.get(lockKey);if (currentValue != null && Long.parseLong(currentValue) > System.currentTimeMillis()) {jedis.del(lockKey);}}
}

3.3 使用示例

以下是一个使用Redis分布式锁的示例：

package cn.juwatech.lock;import redis.clients.jedis.Jedis;public class RedisDistributedLockExample {public static void main(String[] args) {Jedis jedis = new Jedis("localhost", 6379);RedisDistributedLock lock = new RedisDistributedLock(jedis, "lockKey", 5000);if (lock.lock()) {try {// 执行业务逻辑System.out.println("获得锁，执行任务");} finally {lock.unlock();System.out.println("释放锁");}} else {System.out.println("未获得锁，任务跳过");}}
}

4. 基于Zookeeper的分布式锁

Zookeeper也是一种常用的分布式协调服务，可以用来实现分布式锁。Zookeeper通过创建临时节点来实现分布式锁。

4.1 引入依赖

在pom.xml中添加Zookeeper的依赖：

<dependency><groupId>org.apache.zookeeper</groupId><artifactId>zookeeper</artifactId><version>3.7.0</version>
</dependency>

4.2 分布式锁的实现

接下来，我们实现一个基于Zookeeper的分布式锁工具类：

package cn.juwatech.lock;import org.apache.zookeeper.CreateMode;
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.util.Collections;
import java.util.List;public class ZookeeperDistributedLock {private ZooKeeper zooKeeper;private String lockRoot = "/locks";private String lockName;private String lockPath;public ZookeeperDistributedLock(ZooKeeper zooKeeper, String lockName) {this.zooKeeper = zooKeeper;this.lockName = lockName;}public boolean lock() throws Exception {String path = zooKeeper.create(lockRoot + "/" + lockName + "_", new byte[0],ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);this.lockPath = path;List<String> children = zooKeeper.getChildren(lockRoot, false);Collections.sort(children);if (path.equals(lockRoot + "/" + children.get(0))) {return true;}String prevNode = null;for (String node : children) {if (path.equals(lockRoot + "/" + node)) {break;}prevNode = node;}if (prevNode != null) {Stat stat = zooKeeper.exists(lockRoot + "/" + prevNode, new Watcher() {@Overridepublic void process(WatchedEvent event) {synchronized (this) {notifyAll();}}});if (stat != null) {synchronized (this) {wait();}}}return true;}public void unlock() throws Exception {zooKeeper.delete(this.lockPath, -1);}
}

4.3 使用示例

以下是一个使用Zookeeper分布式锁的示例：

package cn.juwatech.lock;import org.apache.zookeeper.ZooKeeper;public class ZookeeperDistributedLockExample {public static void main(String[] args) throws Exception {ZooKeeper zooKeeper = new ZooKeeper("localhost:2181", 3000, null);ZookeeperDistributedLock lock = new ZookeeperDistributedLock(zooKeeper, "testLock");if (lock.lock()) {try {// 执行业务逻辑System.out.println("获得锁，执行任务");} finally {lock.unlock();System.out.println("释放锁");}} else {System.out.println("未获得锁，任务跳过");}}
}