/**
 * <p>抢红包</P>
 * 1.某个红包的子红包队列：存放着每个红包的金额。数据结构：List, Key=rp-{红包ID}, value=红包金额
 * 2.已抢到红包的用户散列：存放已经抢到红包的用户及金额。数据结构：Hash, Key=rp-gain-{红包ID}， hashKey={用户ID}, hashValue={红包金额}
 *
 * @author hanchao
 */
@Slf4j
public class RedisLuaDemo {
    /**
     * 抢红包的lua脚本
     * KEYS[1] = 红包队列Key
     * KEYS[2] = 抢到红包的用户Hash Key
     * ARGV[1] = 用户ID
     */
    private static final String TEST_SCRIPT = "" +
            //如果用户已经抢到过红包，则返回0
            " if redis.call('hexists',KEYS[2],ARGV[1]) ~= 0 then " +
            "   return 0 " +
            " end " +
            //如果用户没抢到过,先查看红包数量是否足够
            " if redis.call('llen',KEYS[1]) ~= 0 then " +
            //如果仍剩余红包，则取出一个红包
            "   local money = redis.call('rpop',KEYS[1]) " +
            //将用户信息和红包金额保存
            "   redis.call('hset',KEYS[2],ARGV[1],money) " +
            "   return 1 " +
            " end " +
            //如果无红包了，则返回2表示红包已经抢完
            "   return 2 ";

    public static void main(String[] args) throws InterruptedException {
        //红包List Key
        String redPacketKey = "rp-list-9527";
        //抢到红包的用户hash Key
        String gainUserKey = "rp-user-map-9527";
        //红包分发总金额
        Integer sum = 0;
        //红包实际被抢总金额
        AtomicReference<Integer> total = new AtomicReference<>(0);

        //门闩一：以便所有线程同时开始运行
        CountDownLatch switchLatch = new CountDownLatch(1);
        //门闩二：以便所有线程都能运行完成
        CountDownLatch countLatch = new CountDownLatch(10);
        //线程池
        ExecutorService executorService = Executors.newCachedThreadPool();

        Jedis jedis = null;
        try {
            jedis = RedisUtil.getConnection();
            if (Objects.nonNull(jedis)) {
                //先清空
                jedis.del(redPacketKey);
                jedis.del(gainUserKey);

                //预先生成5个红包
                for (int i = 0; i < 5; i++) {
                    int money = RandomUtils.nextInt(100, 150);
                    sum += money;
                    //存入缓存
                    jedis.lpush(redPacketKey, String.valueOf(money));
                }
                List<String> redPacketList = jedis.lrange(redPacketKey, 0, jedis.llen(redPacketKey));
                log.info("共生成{}元的红包,金额分别为:{}", sum, redPacketList);

                //脚本加载之后生成的sha编码
                String scriptSha = jedis.scriptLoad(TEST_SCRIPT);

                //脚本执行所需的Key列表，也可以在脚本中直接写死
                List<String> keyList = Lists.newArrayList(redPacketKey, gainUserKey);

                log.info("=============开始抢红包=============");
                //有7个人抢红包,有些人抢了2次
                for (int i = 0; i < 10; i++) {
                    //有些人手快，抢了多次
                    int finalUserId = i % 7;
                    //进行抢红包
                    executorService.submit(new GrabRedPacketTask(switchLatch, countLatch, finalUserId, scriptSha, keyList));
                }
                switchLatch.countDown();
                executorService.shutdown();
                countLatch.await();

                //显示抢红包情况
                log.info("=============抢红包结束=============");
                Map<String, String> gainUserMap = jedis.hgetAll(gainUserKey);
                gainUserMap.forEach((userId, money) -> {
                    log.info("UserId:{},money:{}", userId, money);
                    Integer now = total.get();
                    total.compareAndSet(now, now + Integer.parseInt(money));
                });
                log.info("共生成{}元的红包,实际被抢红包总额{}元。", sum, total.get());
            }
        } finally {
            //关闭redis
            RedisUtil.close(jedis);
        }
    }
}

抢红包线程：GrabRedPacketTask

通过Redis执行Lua脚本一般需要三个参数：

1. 脚本的sha值，用于定位脚本。
2. keyList，Key参数列表，在脚本中通过KEYS[1]、KEYS[2] … KEYS[n-1]来获取参数。
3. argsList，其他参数列表，在脚本中通过ARGV[1]、ARGV[2] … ARGV[n-1]来获取参数。

/**
 * <p>抢红包线程</P>
 *
 * @author hanchao
 */
@Slf4j
@AllArgsConstructor
public class GrabRedPacketTask implements Runnable {
    /**
     * 门闩一：以便所有线程同时开始运行
     */
    private CountDownLatch switchLatch;
    /**
     * 门闩二：以便所有线程都能运行完成
     */
    private CountDownLatch countLatch;
    /**
     * 用户ID
     */
    private Integer userId;
    /**
     * 抢红包脚本sha
     */
    private String scriptSha;
    /**
     * 抢红包脚本执行所需的Key列表
     */
    private List<String> keyList;

    /**
     * 抢红包
     */
    @Override
    public void run() {
        try {
            switchLatch.await();
        } catch (InterruptedException e) {
            log.error("error");
        }
        //脚本执行所需的其他参数列表，也可以在脚本中直接写死
        List<String> argList = Lists.newArrayList(String.valueOf(userId));

        Jedis jedis = null;
        try {
            //抢红包
            jedis = RedisUtil.getConnection();
            if (Objects.nonNull(jedis)) {
                //这里的脚本利用的是其他地方已经加载好的
                String result = jedis.evalsha(scriptSha, keyList