如何防止秒杀抢购超卖?

可以利用redis的事务加上watch监听方法,具体代码如下!

  1 package com.github.distribute.lock.redis;
  2 
  3 import java.util.list;
  4 import java.util.set;
  5 import java.util.concurrent.executorservice;
  6 import java.util.concurrent.executors;
  7 
  8 import redis.clients.jedis.jedis;
  9 import redis.clients.jedis.transaction;
 10 
 11 /**
 12  * redis乐观锁实例
 13  * @author linbingwen
 14  *
 15  */
 16 public class optimisticlocktest {
 17 
 18     public static void main(string[] args) throws interruptedexception {
 19         long startime=system.currenttimemillis();
 20 
 21         initprduct();
 22         initclient();
 23         printresult();
 24 
 25         long endtime=system.currenttimemillis();
 26         long time=endtime-startime;
 27         system.out.println("程序运行时间： "+time+"ms");
 28 
 29     }
 30 
 31     /**
 32      * 输出结果
 33      */
 34     public static void printresult() {
 35         jedis jedis = redisutil.getinstance().getjedis();
 36         set<string> set = jedis.smembers("clientlist");
 37 
 38         int i = 1;
 39         for (string value : set) {
 40             system.out.println("第" + i++ + "个抢到商品，"+value + " ");
 41         }
 42 
 43         redisutil.returnresource(jedis);
 44     }
 45 
 46     /*
 47      * 初始化顾客开始抢商品
 48      */
 49     public static void initclient() {
 50         executorservice cachedthreadpool = executors.newcachedthreadpool();
 51         int clientnum = 10000;// 模拟客户数目
 52         for (int i = 0; i < clientnum; i++) {
 53             cachedthreadpool.execute(new clientthread(i));
 54         }
 55         cachedthreadpool.shutdown();
 56 
 57         while(true){
 58             if(cachedthreadpool.isterminated()){
 59                 system.out.println("所有的线程都结束了！");
 60                 break;
 61             }
 62             try {
 63                 thread.sleep(1000);
 64             } catch (interruptedexception e) {
 65                 e.printstacktrace();
 66             }
 67         }
 68     }
 69 
 70     /**
 71      * 初始化商品个数
 72      */
 73     public static void initprduct() {
 74         int prdnum = 100;// 商品个数
 75         string key = "prdnum_100001";
 76         string clientlist = "clientlist";// 抢购到商品的顾客列表
 77         jedis jedis = redisutil.getinstance().getjedis();
 78 
 79         if (jedis.exists(key)) {
 80             jedis.del(key);
 81         }
 82 
 83         if (jedis.exists(clientlist)) {
 84             jedis.del(clientlist);
 85         }
 86 
 87         jedis.set(key, string.valueof(prdnum));// 初始化
 88         redisutil.returnresource(jedis);
 89     }
 90 
 91 }
 92 
 93 /**
 94  * 顾客线程
 95  *
 96  * @author linbingwen
 97  *
 98  */
 99 class clientthread implements runnable {
100     jedis jedis = null;
101     string key = "prdnum_10001";// 商品主键
102     string clientlist = "clientlist";//// 抢购到商品的顾客列表主键
103     string clientname;
104 
105     public clientthread(int num) {
106         clientname = "编号=" + num;
107     }
108 
109     public void run() {
110         try {
111             thread.sleep((int)(math.random()*5000));// 随机睡眠一下
112         } catch (interruptedexception e1) {
113         }
114         while (true) {
115             system.out.println("顾客:" + clientname + "开始抢商品");
116             jedis = redisutil.getinstance().getjedis();
117             try {
118                 jedis.watch(key);
119                 int prdnum = integer.parseint(jedis.get(key));// 当前商品个数
120                 if (prdnum > 0) {
121                     transaction transaction = jedis.multi();
122                     transaction.set(key, string.valueof(prdnum - 1));
123                     list<object> result = transaction.exec();
124                     if (result == null || result.isempty()) {
125                         system.out.println("悲剧了，顾客:" + clientname + "没有抢到商品");// 可能是watch-key被外部修改，或者是数据操作被驳回
126                     } else {
127                         jedis.sadd(clientlist, clientname);// 抢到商品记录一下
128                         system.out.println("好高兴，顾客:" + clientname + "抢到商品");
129                         break;
130                     }
131                 } else {
132                     system.out.println("悲剧了，库存为0，顾客:" + clientname + "没有抢到商品");
133                     break;
134                 }
135             } catch (exception e) {
136                 e.printstacktrace();
137             } finally {
138                 jedis.unwatch();
139                 redisutil.returnresource(jedis);
140             }
141 
142         }
143     }
144 
145 }