Redis分布式锁实践-优快云博客

本文介绍如何使用Redis的SETNX命令实现简单的分布式锁，并提供了一个基于Java的实现案例，包括Maven依赖配置、Jedis连接池配置及锁的获取与释放过程。

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Redis为单进程单线程模式，采用队列模式将并发访问变成串行访问，且多客户端对Redis的连接并不存在竞争关系。redis的SETNX命令可以方便的实现分布式锁。

maven依赖：

<!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>4.3.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>2.9.0</version>
</dependency>

初始化jedis

@Configuration
public class JedisConfig {
    @Bean
    @Order(1)
    public JedisPoolConfig jedisPoolConfig() {
        JedisPoolConfig poolConfig = new JedisPoolConfig();
        poolConfig.setMaxIdle(10);
        poolConfig.setMaxTotal(30);
        return poolConfig;
    }

    @Bean
    @Order(2)
    public JedisPool jedisPool(JedisPoolConfig jedisPoolConfig) {
        return new JedisPool(jedisPoolConfig,
                "192.168.1.81",
                6379,
                3000,
                "password");
    }
    @Bean
    @Order(3)
    public JedisLock jedisLock(JedisPool jedisPool){
        JedisLock jedisLock = new JedisLock();
        jedisLock.setJedisPool(jedisPool);
        return jedisLock;
    }
}

public class JedisLock {
    private static final String key = "LOCK";
    private static final String      SUCCESS         = "OK";
    JedisPool jedisPool;
    public String getLock(int lockTimout){
        String value = null;
        try {
            Jedis jedis = jedisPool.getResource();
            long end = System.currentTimeMillis() + lockTimout;
            Random random = new Random();
            value = UUID.randomUUID().toString();
            while (System.currentTimeMillis()<end){
                String response = jedis.set(key, value, "NX", "EX", lockTimout);
                if (SUCCESS.equals(response)){
                    //成功获取锁,用完记得释放
                    System.out.println("成功获得锁 response:"+response+",value:"+value);
                    return value;
                }
                TimeUnit.MILLISECONDS.sleep(Math.max(20, random.nextInt(100)));
            }
        }catch (Exception e){
            e.printStackTrace();
        }
        System.out.println("超时未获得锁。。。。");
        return null;
    }
    public boolean releaseLock(String value){
        try {
            Jedis jedis = jedisPool.getResource();
            jedis.watch(key);
            if (StringUtils.pathEquals(value,jedis.get(key))){
                Transaction transaction = jedis.multi();
                transaction.del(key);
                List<Object> list = transaction.exec();
                jedis.unwatch();
                if (null != list){
                    return true;
                }
            }
        }catch (Exception e){
            e.printStackTrace();
        }
        return false;
    }

    /**
     * Setter method for property <tt>jedisPool</tt>.
     *
     * @param jedisPool value to be assigned to property jedisPool
     */
    public void setJedisPool(JedisPool jedisPool) {
        this.jedisPool = jedisPool;
    }
}

测试：

public class JedisTest {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(JedisConfig.class);
        JedisLock jedisLock = (JedisLock) context.getBean("jedisLock");

        String lock = jedisLock.getLock(10000);
        System.out.println(lock);
        String lock1 = jedisLock.getLock(1000);
        System.out.println(lock1);

        boolean b = jedisLock.releaseLock(lock);
        System.out.println("释放锁："+b);
    }
}