ReentrantLock实现的长轮询

• Java代码
• • ReentrantLock
  • 回调
  • 唤醒
• 前端实现

Java代码

ReentrantLock

/**
     * 获取探测点数据,长轮询实现
     * @param messageId
     * @return
     */
    public JSONObject getToutData(String messageId) {
        Message message = toutMessageCache.get(messageId);
        if (message == null) {
            // 等待
            lock.lock();
            try {
                Condition condition = lock.newCondition();
                conditionMap.put(messageId + "_data", condition);
                condition.await(CONNECTION_HOLD_TIMEOUT, TimeUnit.SECONDS);
            } catch (InterruptedException e) {
                // 等待超时， do nothing
            } finally {
                lock.unlock();
            }
        }

        // 再次尝试获取
        message = toutMessageCache.get(messageId);
        if (message == null) {
            // 如果还没有， 返回空对象
            return null;
        }

        byte[] bytes = message.getDataBytes();
        if (bytes == null) {
            return null;
        }
        String resStr = new String(bytes, StandardCharsets.UTF_8);
//        log.info("resStr: {}", resStr);
        JSONObject resObj;
        try {
            resObj = new JSONObject(resStr);
            resObj.put("invokeTime", DateUtil.format(new Date(resObj.getLong("invokeTime")), DatePattern.NORM_DATETIME_MS_PATTERN));
        } catch (Exception e) {
            resObj = new JSONObject();
        }

        return resObj;
    }

回调

public void callback(Message message) {
    String messageId = message.getId();
    toutMessageCache.put(message.getId(), message);
    String messageDataId = messageId + "_data";
    if (conditionMap.containsKey(messageDataId)) {
        lock.lock();
        try {
            Condition condition = conditionMap.get(messageDataId);
            condition.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
            conditionMap.remove(messageDataId);
        }
    }
}

唤醒

public void distribute(Message message, ChannelHandlerContext ctx) {
   MessageType messageType = message.getMessageType();
   switch (messageType) {
       case TOUT_DATA_RESPONSE:
           // 探点数据响应
           toutService.callback(message);
           break;
   }

}

前端实现

let that = this
function getData() {
     if (toutStatus === statusEnum.start) {
         getToutData({
             linkId
         }).then(res => {
             if (res.code === ERROR_CODE_OK) {
                 that.toutData = res.data
                 toutStatus = statusEnum.resData
                 that._btnStatus()
             } else {
                 getData()
             }
         })
     }
 }

 // 递归循环调用
 getData()