使用redis实现分布式锁
    redis命令：set users 10 nx ex 12 原子性命令

    1. //使用uuid，解决锁释放的问题
    2. @GetMapping
    3. public void testLock() throws InterruptedException {
    4.     String uuid = UUID.randomUUID().toString();
    5.     Boolean b_lock = redisTemplate.opsForValue().setIfAbsent("lock", uuid, 10, TimeUnit.SECONDS);
    6.     if(b_lock){
    7.         Object value = redisTemplate.opsForValue().get("num");
    8.         if(StringUtils.isEmpty(value)){
    9.             return;
    10.         }
    11.         int num = Integer.parseInt(value + "");
    12.         redisTemplate.opsForValue().set("num",++num);
    13.         Object lockUUID = redisTemplate.opsForValue().get("lock");
    14.         if(uuid.equals(lockUUID.toString())){
    15.             redisTemplate.delete("lock");
    16.         }
    17.     }else{
    18.         Thread.sleep(100);
    19.         testLock();
    20.     }
    21. }