基于redis的分布式锁简单实现

/**
 * 主要用于在分布式环境下对于共享资源的操作进行锁定
 */
public class RedisLock {
 
    private RedisTemplate redisTemplate;
 
    //获取锁最长等待时间；10秒
    private static final long WAIT_TIME_OUT = 10 * 1000;
 
    //锁的过期时间；3秒
    private static final int LOCK_EXPIRE_TIME = 3 * 1000;
 
    public RedisLock(RedisTemplate redisTemplate) {
        this.redisTemplate = redisTemplate;
    }
 
    /**
     * 在一定的限定时间内 获取某一类资源或操作的锁
     *
     * @param key 键名（可以随便指定；一般为某一类资源或操作命名）
     * @return true or false
     */
    public Boolean lock(String key) throws InterruptedException {
        long timeOut = WAIT_TIME_OUT;
        while (timeOut > 0) {
            long expireTime = System.currentTimeMillis() + LOCK_EXPIRE_TIME;
            Boolean isExists = redisTemplate.boundValueOps(key).setIfAbsent(expireTime);
            if (isExists) {//获取锁成功，直接返回
                return true;
            }
 
            //获取锁失败，查看是否锁已经超时
            long oldExpireTime = (long) redisTemplate.boundValueOps(key).get();
            if (oldExpireTime < System.currentTimeMillis()) {//锁已经超时
                //自行尝试解锁并获取锁
                long newExpireTime = System.currentTimeMillis() + LOCK_EXPIRE_TIME;
                long oldExpireTime2 = (long) redisTemplate.boundValueOps(key).getAndSet(newExpireTime);
                if (oldExpireTime == oldExpireTime2) {
                    //没有被其它线程设置并获取，说明获取锁成功
                    return true;
                }
            }
 
            //沉睡随机几百毫秒再去尝试获取锁
            long sleepTime = (long) (Math.random() * 1000);
            //递减等待获取锁的时间
            timeOut = timeOut - sleepTime;
 
            Thread.sleep(sleepTime);
        }
        return false;
    }
 
    /**
     * 释放某一类资源或操作的锁
     *
     * @param key key 键名（与加锁时候的key要一致）
     */
    public void unlock(String key) {
        long expireTimeMillis = (long) redisTemplate.boundValueOps(key).get();
        if (System.currentTimeMillis() < expireTimeMillis) {
            //如果释放锁的时候没有超时才需要释放锁；不然这是可能被其它线程已经获取到的锁，不应该把其它线程获取到的锁给释放了
            redisTemplate.delete(key);
        }
    }
}

来源：https://blog.csdn.net/qq_39581763/article/details/100015407