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
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";
}
}