java Servlet Filter 攔截Ajax請求

在做登錄驗證的時候,攔截ajax請求，並給出提示，登錄超時

java代碼

String requestType = request.getHeader("X-Requested-With");//請求類型 判定是否為ajax請求
if("XMLHttpRequest".equalsIgnoreCase(requestType)){//ajax請求
      response.setHeader("sessionstatus", "timeout");  
      response.sendError(518, "session timeout.");  
}

 js代碼

//ajax請求登錄驗證
$.ajaxSetup({
    type: 'POST',
    complete: function(xhr,status) {
	    var sessionStatus = xhr.getResponseHeader('sessionstatus');
		if(sessionStatus == 'timeout') {
			$.messager.alert("登錄失效","由於您長時間未操作,登錄已失效,請重新登錄","info",function(){
				parent.location.href = "login.html";
			});   
		}
    }
});