基于Redis 实现分布式锁

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本文链接： https://blog.csdn.net/HandSome_He/article/details/100381907

package com.example.demo.redis;

import org.springframework.stereotype.Component;
import redis.clients.jedis.Jedis;

import java.util.Collections;

/**
 * @Author Xiao  HE
 * @Create Time 2019/9/2 16:33
 **/
@Component
public class RedisTool {
    //Redis 执行成功返回
    private static final String LOCK_SUCCESS = "OK";
    // NX是不存在时才set， XX是存在时才set， EX是秒，PX是毫秒
    private static final String SET_IF_NOT_EXIST = "NX";
    // 设置 过期时间类型  EX = 秒  PX = 毫秒
    private static final String SET_WITH_EXPIRE_TIME = "EX";

    /**
     * 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;
    }
    private static final Long RELEASE_SUCCESS = 1L;
    /**
     * 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) {
        String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
        Object result = jedis.eval(script, Collections.singletonList(lockKey), Collections.singletonList(requestId));
        if (RELEASE_SUCCESS.equals(result)) {
            return true;
        }
        return false;
    }

}

package com.example.demo.MyTest;

import com.example.demo.redis.RedisTool;
import com.example.demo.service.UserService;
import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;
import lombok.Data;
import org.apache.logging.log4j.util.Strings;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.data.redis.connection.RedisConnection;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.test.context.junit4.SpringRunner;
import redis.clients.jedis.Jedis;

import java.util.List;
import java.util.Map;
import java.util.UUID;

import static redis.clients.jedis.Protocol.Command.EXPIRE;

/**
 * @Author Xiao  HE
 * @Create Time 2019/8/30 21:41
 **/
@SpringBootTest
@RunWith(SpringRunner.class)
public class MyTest2 {

    @Value("${spring.redis.host}")
    public static String host;

    static boolean isOpenExpirationRenewal = true;

    public static void main(String[] args) throws Exception{
        Jedis jedis = new Jedis(host);
        String lockKey = "zhendifan";
        String lockValue = UUID.randomUUID().toString();
        //设置过期时间未 120 秒
        boolean redisBoolean = RedisTool.tryGetDistributedLock(jedis, lockKey, lockValue, 120);
        if(redisBoolean){
            System.out.println("拿到redis 锁 进入方法");
            Thread thread = new Thread(new ExpirationRenewal(jedis, lockKey, lockValue));
            thread.start(); //启动线程
            try{
                System.out.println("逻辑代码执行中.........");
                //假设需要执行两分钟
                Thread.sleep(120000);
            }catch (Exception e){
                throw new Exception("发生异常！异常信息"+e);
            }finally {
                // 关闭线程
                isOpenExpirationRenewal=false;
                thread.interrupt();
                //释放Redis 锁
                RedisTool.releaseDistributedLock(jedis,lockKey,lockValue);
            }
        }
    }
    /*
     * 刷新Key 过期时间 保证业务处理时间大于过期时间
     * @param jedis Redis客户端
     * @@param lockKey 锁
     * @param requestId 请求标识
     * */
    @Data
    public static class ExpirationRenewal implements Runnable{

        private Jedis jedis;

        private String lockKey;

        private String lockValue;

        public ExpirationRenewal(Jedis jedis, String lockKey, String lockValue) {
            this.jedis = jedis;
            this.lockKey = lockKey;
            this.lockValue = lockValue;
        }
        @Override
        public void run(){
            //监测 锁过期时间
            while (isOpenExpirationRenewal){
                System.out.println("执行延迟失效时间中...");
                String checkAndExpireScript = "if redis.call('get', KEYS[1]) == ARGV[1] then " +
                        "return redis.call('expire',KEYS[1],ARGV[2]) " +
                        "else " +
                        "return 0 end";
                //  锁过期后重新给锁设置过期时间 15 秒
                jedis.eval(checkAndExpireScript, 1, this.lockKey, this.lockValue, "15");
                //如果不行 就直接Set 去重新设置过期时间
                try {
                    //休眠10秒
                    Thread.sleep(10000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

详细内容请看: Redis分布式锁的正确实现方式（Java版）

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