秒杀实现 乐观锁

@RestController
public class HelloWorld {
    @GetMapping("hello")
    public Result hello(){
        Integer uid = (int) (Math.random()*100);
        String userKey = "sk:1010:user";
        String kcKey = "sk:1010:qt";
        Jedis jedis = new Jedis("42.193.140.45", 6379);
        if(jedis.get(kcKey) == null){
            System.out.println("秒杀未开始");
            jedis.close();
            return Result.fail();
        }
        //判断是否重复秒杀
        if(jedis.sismember(userKey,uid.toString())){
            System.out.println("你已经秒杀了，不能重复秒杀");
            jedis.close();
            return Result.fail();
        }
        if(Integer.parseInt(jedis.get(kcKey))<=0){
            System.out.println("秒杀结束");
            jedis.close();
            return Result.fail();
        }
        jedis.decr(kcKey);
        jedis.sadd(userKey,uid.toString());
        System.out.println("秒杀成功");
        jedis.close();
        return Result.ok();
    }
    @GetMapping("init")
    public Result init(){
        String userKey = "sk:1010:user";
        Jedis jedis = new Jedis("42.193.140.45", 6379);
        jedis.set("sk:1010:qt","10");
        jedis.del(userKey);
        jedis.close();
        return Result.ok();
    }
    @GetMapping("info")
    public Result info(){
        Jedis jedis = new Jedis("42.193.140.45", 6379);
        Set<String> smembers = jedis.smembers("sk:1010:user");
        System.out.println(smembers);
        String s = jedis.get("sk:1010:qt");
        System.out.println(s);
        return Result.ok();
    }
}

并发  执行之后会出现负值

1. 添加乐观锁

public Result hello(){
    Integer uid = (int) (Math.random()*100);
    String userKey = "sk:1010:user";
    String kcKey = "sk:1010:qt";
    Jedis jedis = new Jedis("42.193.140.45", 6379);
    //1 添加监视
    jedis.watch(kcKey);
    if(jedis.get(kcKey) == null){
        System.out.println("秒杀未开始");
        jedis.close();
        return Result.fail();
    }
    //判断是否重复秒杀
    if(jedis.sismember(userKey,uid.toString())){
        System.out.println("你已经秒杀了，不能重复秒杀");
        jedis.close();
        return Result.fail();
    }
    if(Integer.parseInt(jedis.get(kcKey))<=0){
        System.out.println("秒杀结束");
        jedis.close();
        return Result.fail();
    }
    //2 开启事务
    Transaction multi = jedis.multi();
    //3 组队
    multi.decr(kcKey);
    //jedis.decr(kcKey);
    //jedis.sadd(userKey,uid.toString());
    multi.sadd(userKey,uid.toString());
    //4 执行
    List<Object> exec = multi.exec();
    if(exec == null || exec.size() == 0){
        System.out.println("秒杀失败");
        jedis.close();
        return Result.fail();
    }
    System.out.println("秒杀成功");
    jedis.close();
    return Result.ok();
}

结果：