redis 单机加锁

加锁使用新版的api set (key, value, nx, px, expireTime)，保证原子性，以及超时机制
解锁使用lua表达式，判断解锁人是否是加锁人，防止超时后解了别人的锁。

package com.utils;

import java.util.Collections;
import java.util.UUID;

import redis.clients.jedis.Jedis;

public class RedisTool {

private static final String LOCK_SUCCESS = "OK";
private static final String SET_IF_NOT_EXIST = "NX";
private static final String SET_WITH_EXPIRE_TIME = "PX";
private static final String SCRIPT = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
private static final Long RELEASE_SUCCESS = 1L;

// test
private int count = 0;

/**
 * 获取请求Id 
 * @return 返回UUID
 */
public static String getRequestId(){
    return UUID.randomUUID().toString();
}

/**
 * 尝试获取分布式锁
 * @param jedis Redis客户端
 * @param lockKey 锁
 * @param requestId 请求标识
 * @param expireTime 超期时间
 * @return 是否获取成功
 */
public static boolean tryGetDistributedLock(Jedis jedis, String lockKey, String requestId, int expireTime) {

    String result = jedis.set(lockKey, requestId, SET_IF_NOT_EXIST, SET_WITH_EXPIRE_TIME, expireTime);

    if (LOCK_SUCCESS.equals(result)) {
        return true;
    }
    return false;
}


/**
 * 释放分布式锁
 * @param jedis Redis客户端
 * @param lockKey 锁
 * @param requestId 请求标识
 * @return 是否释放成功
 */
public static boolean releaseDistributedLock(Jedis jedis, String lockKey, String requestId) {

    Object result = jedis.eval(SCRIPT, Collections.singletonList(lockKey), Collections.singletonList(requestId));

    if (RELEASE_SUCCESS.equals(result)) {
        return true;
    }
    return false;
}

public static void main(String[] args) {
    RedisTool redisTool = new RedisTool();
    redisTool.testDistributedLock();
}

public void testDistributedLock() {
    for (int i = 0; i < 10; i++) {
        new Thread(new Runnable() {

            @Override
            public void run() {
                Jedis jedis = new Jedis("localhost");
                String lockKey = "lock";
                String requestId = getRequestId();
                // 加锁
                if (tryGetDistributedLock(jedis, lockKey, requestId, 10)) {
                    count++;
                    System.out.println(requestId + ":" + count);
                    // 解锁
                    releaseDistributedLock(jedis, lockKey, requestId);
                } else {
                    System.out.println(requestId + ": tryGetDistributedLock fail");
                }

            }
        }).start();
    }
}

}