Notify Users before session expires

[Meet Gaurav]

Hi,

I saw in few sites, the users were getting a alert before the session expires. How to achieve that..

is their any way we can invoke the Javascript window.open from JSP before the session time.. Please assist me

[Paul Sturrock]

It's usually something like a JavaScript timer plus an AJAX request to stop the session expiring (assuming the user responds) or remove the popup if they don't

[Meet Gaurav]

Thanks Paul..

I googled and I got the below code.

var secondsBeforeExpire = <c:out value="${pageContext.session.maxInactiveInterval}"/>;
	  alert(secondsBeforeExpire);
	      
	      var timeToDecide = 15; // Give client 15 seconds to choose.
	      setTimeout(function() {
	          alert('Your session is about to timeout in ' + timeToDecide + ' seconds!')
	      }, (secondsBeforeExpire - timeToDecide) * 1000);
	      

I guess I need to submit 1 ajax request to server saving client is alive.. Am I rite.

Thanks

[Paul Sturrock]

Yeah.

[Meet Gaurav]

Paul I got struck in AJAX call.. Please help

Call is not going to my handler..

	  function submitExtend()
	  {
	    alert("AJAX CALL");
		
		var params= 'userName=xxxxx' + '&password=aaaaa';
   var urlpost= 'MainHandler.do' ;
   makeGetRequest( urlpost, params );
	  }
	  
	  
	  function createRequestObject() {
		var tmpXmlHttpObject;
		if(window.XMLHttpRequest) {
			tmpXmlHttpObject = new XMLHttpRequest();
		} else if (window.ActivexObject) {
			tmpXmlHttpObject = new ActiveXobject("Microsoft.XMLHTTP");
		}
		return tmpXmlHttpObject;
	}
	
	var http;
function makeGetRequest(url, params) {
alert(params);
alert(url);
		http = createRequestObject();
		http.open('POST', url, true);
                http.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
                http.setRequestHeader("Content-length", params.length);
		http.onreadystatechange = processResponse;
		http.send(params);
	}

	
	function processResponse() {
		if(http.readyState == 4) {
			document.getElementById('header').innerHTML = "You have not typed Anything";
	}
	}

[Bear Bibeault]

Ajax is much much easier if you use one of the popular JavaScript libraries such as jQuery or Dojo.

[Meet Gaurav]

Finally This code works fine...... Ajax call is going to server now..

	  <script type="text/javascript">
	   
	  function getXMLObject()  //XML OBJECT
	  {
	     var xmlHttp = false;
	     try {
	       xmlHttp = new ActiveXObject("Msxml2.XMLHTTP")  // For Old Microsoft Browsers
	     }
	     catch (e) {
	       try {
	         xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")  // For Microsoft IE 6.0+
	       }
	       catch (e2) {
	         xmlHttp = false   // No Browser accepts the XMLHTTP Object then false
	       }
	     }
	     if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
	       xmlHttp = new XMLHttpRequest();        //For Mozilla, Opera Browsers
	     }
	     return xmlHttp;  // Mandatory Statement returning the ajax object created
	  }
	   
	  var xmlhttp = new getXMLObject();	//xmlhttp holds the ajax object
	   
	  function ajaxFunction() {
	    var getdate = new Date();  //Used to prevent caching during ajax call
	    if(xmlhttp) { 
	      xmlhttp.open("GET","MainHandler.do",true); //gettime will be the servlet name
	      xmlhttp.onreadystatechange  = handleServerResponse;
	      xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
	      xmlhttp.send(null);
	      alert("Sent.........");
	    }
	  }
	   
	  function handleServerResponse() {
	     if (xmlhttp.readyState == 4) {
	       if(xmlhttp.status == 200) {
	         document.myForm.time.value=xmlhttp.responseText; //Update the HTML Form element 
	       }
	       else {
	          alert("Error during AJAX call. Please try again");
	       }
	     }
	  }
</script>

Sometimes am getting below alert
alert("Error during AJAX call. Please try again");

But still the call is going to Action handler(servlet).. Someone please assist me why am getting this error.