code: public boolean set(String value, Date expireAt) {
  		if (value == null)
  			return false;
  		try {
  			boolean result = getJedisCommands(groupName).set(key, value).equals(RESP_OK);
  			if(result){
  				result = setExpireAt(expireAt);
  				//set可能是更新缓存，所以统一通知各节点清除本地缓存
  				Level1CacheSupport.getInstance().publishSyncEvent(key);
  			}
  			return result;
  		} finally {
  			getJedisProvider(groupName).release();
  		}
  	}
docs: 检查给定 key 是否存在。
  @return