關於GWT中RequestBuilder的緩存問題

今天遇到一個需求, 就是在前段每隔1分鐘遍發送請求到後臺讀取當前數據庫狀態, 本來感覺很簡單的問題花了好久才解決,而罪魁禍首就是緩存, 原代碼如下:

	public  void checkDBStatusTrigger(){

    	Timer refreshTimer = new Timer() {
			public void run() {

				RequestBuilder builder = new RequestBuilder(RequestBuilder.GET,  "chcekDBStatus.do");
				builder.setHeader("Cache-Control","no-cache"); 

				try {
					builder.sendRequest(null, new RequestCallback() {
						@Override
						public void onResponseReceived(Request request, Response response) {
							String flag = response.getText();
							//Window.alert("Responose:"+flag);
							if(flag!=null && !"".equals(flag))
								GwtConstants.DB_STATUS = Boolean.parseBoolean(flag);	
							else
								GwtConstants.DB_STATUS = false;
						}

						@Override
						public void onError(Request request, Throwable e) {
							GwtConstants.DB_STATUS = false;
						}
					});
				} catch (Exception e) {
					GwtConstants.DB_STATUS = false;
					e.printStackTrace();
				}	
			}
    	};

    	refreshTimer.scheduleRepeating(REFRESH_INTERNAL);
    }

很簡單的一段代碼, 但奇怪的是隻有第一次訪問後臺代碼了,以後始終不再訪問後臺, 搜了大量參考之後得知貌似得傳一個變量到後臺, 所以改進一小段代碼後問題就解決了.


RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, "chcekDBStatus.do?sessionid=(new Date().toString()));

太蛋疼的問題了, 具體原因現在還不知道...