Redis高并发分布式锁(学习总结)

0. 为什么要设计分布式锁？

正常的业务操作在多线程情况下不能实现原子性，要么全部不执行，要么全部执行。在分布式场景下更是会出现这种多个线程对同一条数据操作的情况。

1. redis分布式锁实现

官方推荐传送门！！！

下面是redis官方推荐的三款客户端： 

 1.1 引入依赖

<dependency>
			<groupId>org.redisson</groupId>
			<artifactId>redisson</artifactId>
			<version>3.6.5</version>
		</dependency>

 1.2 代码实现reddison

package com.redisson;

import org.redisson.Redisson;
import org.redisson.RedissonRedLock;
import org.redisson.api.RLock;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.TimeUnit;

@RestController
public class IndexController {

    @Autowired
    private Redisson redisson;
    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @RequestMapping("/deduct_stock")
    public String deductStock() {
        String lockKey = "product_101";

        RLock redissonLock = redisson.getLock(lockKey);
        try {
            redissonLock.lock();  //setIfAbsent(lockKey, clientId, 30, TimeUnit.SECONDS);
            int stock = Integer.parseInt(stringRedisTemplate.opsForValue().get("stock")); // jedis.get("stock")
            if (stock > 0) {
                int realStock = stock - 1;
                stringRedisTemplate.opsForValue().set("stock", realStock + ""); // jedis.set(key,value)
                System.out.println("扣减成功，剩余库存:" + realStock);
            } else {
                System.out.println("扣减失败，库存不足");
            }
        } finally {
            redissonLock.unlock();
        }

        return "end";
    }

}

1.3 redisson内部源码实现

1.3.1 reddsion分布式锁架构图