如何防止秒殺搶購超賣?

可以利用redis的事務加上watch監聽方法,具體代碼如下!

  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樂觀鎖實例
 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("程式運行時間： "+Time+"ms");
 28 
 29     }
 30 
 31     /**
 32      * 輸出結果
 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++ + "個搶到商品，"+value + " ");
 41         }
 42 
 43         RedisUtil.returnResource(jedis);
 44     }
 45 
 46     /*
 47      * 初始化顧客開始搶商品
 48      */
 49     public static void initClient() {
 50         ExecutorService cachedThreadPool = Executors.newCachedThreadPool();
 51         int clientNum = 10000;// 模擬客戶數目
 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("所有的線程都結束了！");
 60                 break;
 61             }
 62             try {
 63                 Thread.sleep(1000);
 64             } catch (InterruptedException e) {
 65                 e.printStackTrace();
 66             }
 67         }
 68     }
 69 
 70     /**
 71      * 初始化商品個數
 72      */
 73     public static void initPrduct() {
 74         int prdNum = 100;// 商品個數
 75         String key = "prdNum_100001";
 76         String clientList = "clientList";// 搶購到商品的顧客列表
 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  * 顧客線程
 95  *
 96  * @author linbingwen
 97  *
 98  */
 99 class ClientThread implements Runnable {
100     Jedis jedis = null;
101     String key = "prdNum_10001";// 商品主鍵
102     String clientList = "clientList";//// 搶購到商品的顧客列表主鍵
103     String clientName;
104 
105     public ClientThread(int num) {
106         clientName = "編號=" + num;
107     }
108 
109     public void run() {
110         try {
111             Thread.sleep((int)(Math.random()*5000));// 隨機睡眠一下
112         } catch (InterruptedException e1) {
113         }
114         while (true) {
115             System.out.println("顧客:" + clientName + "開始搶商品");
116             jedis = RedisUtil.getInstance().getJedis();
117             try {
118                 jedis.watch(key);
119                 int prdNum = Integer.parseInt(jedis.get(key));// 當前商品個數
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("悲劇了，顧客:" + clientName + "沒有搶到商品");// 可能是watch-key被外部修改，或者是數據操作被駁回
126                     } else {
127                         jedis.sadd(clientList, clientName);// 搶到商品記錄一下
128                         System.out.println("好高興，顧客:" + clientName + "搶到商品");
129                         break;
130                     }
131                 } else {
132                     System.out.println("悲劇了，庫存為0，顧客:" + clientName + "沒有搶到商品");
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 }