code: public <V> V execute(RedisCallback<V> cb) {
          Jedis jedis = jedisPool.getResource();
          boolean success = true;
          try {
              return cb.execute(jedis);
          } catch (JedisException e) {
              success = false;
              if (jedis != null) {
                  jedisPool.returnBrokenResource(jedis);
              }
              throw e;
          } finally {
              if (success) {
                  jedisPool.returnResource(jedis);
              }
          }
      }
docs: execute a redis operation
  @param cb callback
  @param <V> return type
  @return result