1.思路
在redis提供了incr命令进行递增操作，可以保证原子性。利用watch实现也可以实现递增递减的操作。
WATCH命令可以监控一个或多个键，一旦其中有一个键被修改（或删除），之后的事务就不会执行。监控一直持续到EXEC命令（事务中的命令是在EXEC之后才执行的，所以在MULTI命令后可以修改WATCH监控的键值）
2.代码实现
public class SecKillDemo implements Runnable {
private Jedis jedis = new Jedis("192.168.99.100", 6379);
private String customerName;
private String key;
public SecKillDemo(String customerName, String key) {
this.customerName = customerName;
this.key = key;
}
@Override
public void run() {
boolean success = false;
String data;
int currentNum;
while (!success) {//可重复抢购直到成功
//通过watch实现redis的incr(原子递增操作)
jedis.watch(key);
data = jedis.get(key);
currentNum = Integer.parseInt(data);
if (currentNum > 0) {
//开启事务
Transaction transaction = jedis.multi();
//设置新值,如果key的值被其它连接的客户端修改，那么当前连接的exec命令将执行失败
currentNum--;
transaction.set(key, String.valueOf(currentNum));
List res = transaction.exec();
if (res.size() == 0) {
System.out.println(customerName + " 抢购失败");
success = false;
} else {
success = true;
System.out.println(customerName + " 抢购成功,[" + key + "]剩余：" + currentNum);
}
} else {
System.out.println("商品售空,活动结束!");
System.exit(0);
}
}
}
}
3.测试
public class SecKillTest {
private static String key = "macbook";
private static String num = "100";
private static ExecutorService executorService = Executors.newFixedThreadPool(8);
@Before
public void before() {
Jedis jedis = new Jedis("192.168.99.100");
String script = "redis.call('del',KEYS[1]);return redis.call('set',KEYS[1],ARGV[1])";
jedis.eval(script, Collections.singletonList(key), Collections.singletonList(num));
jedis.close();
}
@Test
public void test() {
}
public static void main(String[] args) {
try{
for (int i = 1; i <= 600; i++) {
executorService.submit(new SecKillDemo("顾客"+i,key));
}
}finally {
executorService.shutdown();
}
}
}
