redis事物实现秒杀

使用Redis事物实现多人秒杀同一款商品
① 设计商品在Redis中的存储，key值为sk:"+prodid+":qt，商品的值为商品的数量（string类型）
② 设计秒杀成功的用户清单在Redis中的存储，key为sk:"+prodid+":usr，保存秒杀成功的用户使用set集合保存

1、前端页面index.jsp

前端jsp页面点击秒杀按钮调用后台doseckill
2、编写后台servlet（SecKillServlet）

public class SecKillServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public SecKillServlet() {
        super();
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String userid = new Random().nextInt(50000) +"" ; 
        String prodid =request.getParameter("prodid");
        boolean if_success=SecKill_redis.doSecKill(userid,prodid);
        response.getWriter().print(if_success);
    }
}

3、在web.xml中配置servlet

    
    
      seckill
      
        
        doseckill
        doseckill
        com.atguigu.SecKillServlet
      
      
        doseckill
        /doseckill
      
    

4、SecKill_redis类中实现doSecKill方法
如果不加redis事务，会出现超卖问题

public class SecKill_redis {
    
    private static final  org.slf4j.Logger logger =LoggerFactory.getLogger(SecKill_redis.class) ;

    public static boolean doSecKill(String uid,String prodid) throws IOException {
        //通过连接池，解决连接超时问题
        JedisPool jedisPool = JedisPoolUtil.getJedisPoolInstance();
        
        Jedis jedis =jedisPool.getResource();//如果jedis是从连接池获取的，当执行close时回收到连接池中，不会关闭
        //1.获取redis存储相应key
        String qtKey="sk:"+prodid+":qt";
        String usrKey="sk:"+prodid+":usr";
        
        //判断用户是否秒杀成功过
        if(jedis.sismember(usrKey, uid)){
            System.out.println("已经秒杀过！！！");
            jedis.close();
            return false;
        }
        
        jedis.watch(qtKey);
        //对商品判断
        String qtValue=jedis.get(qtKey);
        if(qtValue==null){
            System.out.println("商品没有初始化！！！");
            jedis.close();
            return false;
        }else{
            int qt=Integer.parseInt(qtValue);
            if(qt==0){
                System.out.println("秒杀失败！");
                jedis.close();
                return false;
            }
        }
        Transaction t=jedis.multi();
        //2.商品减库存
        t.decr(qtKey);
        //3.增加相应用户
        t.sadd(usrKey, uid);
        List