Redis分布式锁

1. 自定义分布式锁：

       //加锁
       public boolean lock(String lockName, String lockTime) {
           //如果key值不存在，则返回 true，且设置 value
           if (redisTemplate.opsForValue().setIfAbsent(lockName, lockTime)) {
               return true;
           }
           //获取lockName的值
           String curVal = (String) redisTemplate.opsForValue().get(lockName);
           //判断是是否超时
           if (!StringUtils.isEmpty(curVal) && Long.parseLong(curVal) < System.currentTimeMillis()) {
               //获得之前的key值，同时设置当前的传入的过期时间lockTime。
               String savedLockTime = (String) redisTemplate.opsForValue().getAndSet(lockName, lockTime);
               //判断存入的lockTime是否是当前传入的lockTime
               if (!StringUtils.isEmpty(savedLockTime) && savedLockTime.equals(curVal)) {
                   return true;
               }
           }
           return false;
       }​
   
       //解锁
       public void unlock(String lockName, String lockTime) {
           try {
               String curVal = (String) redisTemplate.opsForValue().get(lockTime);
               if (!StringUtils.isEmpty(curVal) && curVal.equals(lockName)) {
                   redisTemplate.opsForValue().getOperations().delete(lockTime);
               }
           } catch (Exception e) {
               e.printStackTrace();
           }
       }

    

   加锁代码：

           try {
               String lockName = "lock" + userId;
               String lockTime = String.valueOf(System.currentTimeMillis() + 5000);
               if (lock(lockName, lockTime)) {
                   //TODO
               }
           } finally {
               unlock(lockName, lockTime);
           }​

2. spring-integration-redis中的分布式锁：
   
   1. maven需要引入

      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-data-redis</artifactId>
      </dependency>
      
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-integration</artifactId>
      </dependency>
      
      <dependency>
        <groupId>org.springframework.integration</groupId>
        <artifactId>spring-integration-redis</artifactId>
      </dependency>​

   2. 添加RedisLock配置

      @Bean
      public RedisLockRegistry redisLockRegistry(RedisConnectionFactory redisConnectionFactory) {
          return new RedisLockRegistry(redisConnectionFactory, "redis-lock");
      }

   3. 使用代码

              String key = "lock:" + fieldName + "_" + value;
              Lock lock = redisLockRegistry.obtain(key);
              try {
                  //尝试获取锁，如果获取不到会继续尝试
                  boolean b1 = lock.tryLock(5L, TimeUnit.SECONDS);
                  if (!b1) {
                      return ResponseResult.argumentError("system busy");
                  }
                  //TODO
      
              } catch (Throwable ex) {
                  ex.printStackTrace();
              } finally {
                  lock.unlock();
              }​

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