Question

Question on sessions

Asked by: Micheal_Male

say for instance you have the session timeout set for an application to default which is 30 min. You have a page which is written using spring and jstl tags. The jsp page is connected to the controller. In the jsp i am checking one of the session objects to see if it still exist. If yes good if not then send the user back to the index page which is the login page. However it is frustrating sometime because if the form is big then the user has to login back and fill out the form fields. Is it possible to set the session timeout to one hour for just this one page instead of changing the whole application session ?.

I don't want to refresh the page through a javscript as i will loose all of the form fields. Any input example will be great.

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Asked On: 2009-09-22 at 17:42:26ID24753546
Tags: spring framework
,; j2ee
,; jsp
,; javascript
Topics: Spring
,; JavaScript
,; Asynchronous Javascript and XML (AJAX)
Participating Experts: 2
Points: 125
Comments: 29

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Answers

by: MuraliKanthPosted on 2009-09-22 at 19:24:23ID: 25399582

use the following AJAX code to alert the user about extending the session.
Ajax will not reload /refresh the whole page and its ideal to use.

//servlet code

session = request.getSession();
            StringBuffer xml = new StringBuffer();
xml.append("<?xml version=\"1.0\"?>\n");

       xml.append("<session userid=\"" + (String)session.getAttribute("userId") + "\">\n");
       xml.append("</session>\n");

response.setContentType("text/xml");
response.getWriter().write(xml.toString());
response.getWriter().flush();

/*
 * Returns an new XMLHttpRequest object, or false if the browser
 * doesn't support it
 */
function newXMLHttpRequest()
{
	var xmlreq = false;
 
	// Create XMLHttpRequest object in non-Microsoft browsers
	if (window.XMLHttpRequest)
	{
	  xmlreq = new XMLHttpRequest();
	}
	else if (window.ActiveXObject)
	{
	    try
	    {
	      // Try to create XMLHttpRequest in later versions
	      // of Internet Explorer
	
	      xmlreq = new ActiveXObject("Msxml2.XMLHTTP");
	    }
	    catch (e1)
	    {
			// Failed to create required ActiveXObject
			try
			{
				// Try version supported by older versions
				// of Internet Explorer
				
				xmlreq = new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch (e2)
			{
			  // Unable to create an XMLHttpRequest by any means
			  xmlreq = false;
			}
		}
	}
 
	return xmlreq;
}
 
 
/*
* Returns a function that waits for the specified XMLHttpRequest
* to complete, then passes it XML response to the given handler function.
* req - The XMLHttpRequest whose state is changing
* responseXmlHandler - Function to pass the XML response to
*/
function getReadyStateHandler(req, responseXmlHandler)
{
	// Return an anonymous function that listens to the XMLHttpRequest instance
	return function ()
	{
		// If the request's status is "complete"
		if (req.readyState == 4)
		{
			// Check that we received a successful response from the server
			if (req.status == 200) 
			{
				// Pass the XML payload of the response to the handler function.
				responseXmlHandler(req.responseXML);
			}
			else
			{
				// An HTTP problem has occurred
				alert("HTTP error "+req.status+": "+req.statusText);
			}
		}
	}
}
 
function extendSession(){
  var req = newXMLHttpRequest(); // ajax.js
  req.onreadystatechange = getReadyStateHandler(req, updateSessionInfo);
  req.open("POST", "/servlet/SessionHandler", true);
  req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
  req.send("pageKey=extendSession");
}
 
function updateSessionInfo(sessionXML){
	  var session = sessionXML.getElementsByTagName("session")[0];
	  var userid = session.getAttribute("userid");	   
	  if(userid == 'null' || userid == null){
		  msgToUser();
	  }
}
 
function promptUser(){
  //extensionWanted = false;
  if (confirm('Your login session will expire in 5 minute. Would you like to extend the session?')){
		//extensionWanted = true;
		extendSession();
		setSessionTimeout();
  }
}
 
 
 
function setSessionTimeout(){
      // prompt timeout message 5 mins before timeout
      // it is assume to be 30 mins before timeout
      setTimeout('promptUser()', 25 * 60 * 1000);
      //setTimeout('promptUser()', 1 * 60 * 1000);
      //setTimeout('logout()', 30 * 60 * 1000);
      //setTimeout('promptUser()', 5000);
      //setTimeout('logout()', 10000);
}
 
setSessionTimeout();

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Select all Open in new window

by: HainKurtPosted on 2009-09-22 at 19:38:29ID: 25399630

on server set it to 1 hour...

also, put these logic to your all pages...

on session_start
session("session_created") = now

on every page

if session_timeout goto login page
if (page <> my long page) and (now - session("last_activity") >20) logout (or session.abondon) ; go to login page

what we are doing is setting actual server timeout to 1 hour, but programatically we are setting it to 20 min (for all pages but your long page)

by: Micheal_MalePosted on 2009-09-22 at 19:55:17ID: 25399696

Murali thanks for the response. I am using DWR AJAX Framework unfortunately i was not able to find any method in the documentation which will keep the session alive. However if i can make your code work then this is exactly what i need. Will update in a few

by: Micheal_MalePosted on 2009-09-22 at 19:56:24ID: 25399700

Hainkurt unfortunately there are lots of JSP so to update all the JSP is next to impossible.

by: HainKurtPosted on 2009-09-22 at 20:00:43ID: 25399713

what about just inserting a hidden iframe into your long page, which refreshes the tiny page every 10-20 minutes?

<iframe src="refresh.asp" width=0 height=0/>

and refresh.asp is just a dummy page like this:

<html>
<head>
<meta http-equiv="refresh" content="600">
<title>refresh</title>
</head>
<body><body>
</html>

by: HainKurtPosted on 2009-09-22 at 20:01:48ID: 25399716

I thought you have a header / footer files, which is included by every page :)

bad design... what about the previous solution?

by: HainKurtPosted on 2009-09-22 at 20:04:38ID: 25399720

that page will never expires, but you can create a counter and if it is 6, then you can send

<script>
alert("session ended, you have to start again, sorry");
document.href.src="login.asp";
</script>

or you can implement some other logic...

by: Micheal_MalePosted on 2009-09-22 at 20:05:37ID: 25399723

yes. No headers and footers :(. Hmmm i thought about using iframe and refresh it but was afraid if my values are still going to be intact or not. Let me try that.

by: MuraliKanthPosted on 2009-09-22 at 20:21:07ID: 25399775

@Micheal_Male

the code i have posted is a working version in one of my projects. You need to just give a hit to server to keep ur session alive.Thats what is achieved with my code.

by: Micheal_MalePosted on 2009-09-22 at 20:34:16ID: 25399831

Murali the only issue is that i am using spring framework so i have a controller. However i see in your code you are referencing it to a servlet.

req.open("POST", "/servlet/SessionHandler", true);

I do have a listener class by the name of SessionTracking and over there i implemented HttpSessionListener. In this class i am setting the session time and redirecting it to the login page if there is no session in sessionDestroyed() method.

I don't want to do anything with the login servlet where it sets all the session as it might break something. Just concerned.

by: MuraliKanthPosted on 2009-09-22 at 20:42:26ID: 25399859

HttpSessionListener would get triggered for the session creation/destroy period. Actually if you set session timeout as say 45 mins thn you need to hit the server atleast 5 mins well in advance to reset ur session timeout automatically. For achieving this you need to have a servlet or a controller re-directed to some class where u just return some unique id(userid) for validating the session.

This cycle of giving a hit to server before 5 mins would reset ur session timeout and there by the HttpSessionListener would not be triggered. You can possibly have a indivdual servlet for this purpose or a seperate controller (my knowledge on Spring Controller is limited).

-Murali*

by: Micheal_MalePosted on 2009-09-22 at 21:00:52ID: 25399920

Thanks for your response. Actually i know what an HttpSessionListener will do which i was sure will not achieve the desire result which i am trying to accomplish as you stated in the comment. I am using a MultiActionController and in one of the methods (which is 'Insert' method which inserts the values in the DB) i am already getting the userid from the session. So if the session is not active then a blank page is displayed. However if i write something like this in my jsp :-

<%
session = request.getSession(false);
//now check if the userId is null from the session
//if it is then set the header and redirect the user to the login page
%>

then the user is redirected to the login page. Now if you think this will not work then i think as per you i need to create a seperate servlet which will just have a simple method of getting the useid or validating if the session is still active. And then make it available in web.xml and then use the Ajax code you posted in my long page ? Correct ?

Lastly it looks like the function you posted i will be putting it in my jsp and calling promptuser method in body onload ?

by: MuraliKanthPosted on 2009-09-22 at 21:09:25ID: 25399954

Yes you are correct.

Actually u need to place the functions all in a single .js file and include to the page where u need it.
It would automatically call the servelt or controller at( 25 * 60 * 1000) 25th minute (you can change it as necessary). setSessionTimeout(); would be executed automatically and you need not to call any function explicitly.

i have a additional function msgToUser(){ } where u can redirect to a login page if session has already expired.

by: Micheal_MalePosted on 2009-09-23 at 18:13:19ID: 25409542

Murali. Thanks. I was able to create a servlet and was able to achieve the desired result. Although i must admit that this is a perfect solution for keeping the session alive for a specific page without changing the session timeout. I had alot of other senarios to consider like get the session Id and then increase the timeout for that session. But your example was much more helpful than anyone else.

I will urge to create a blog if possible because while searching on google i could'nt find any good resource on AJAX implementation of refreshing page. Your blog will definitely help other users out just like. Thanks .

by: Micheal_MalePosted on 2009-09-23 at 18:14:12ID: 31632261

With the walkthough murali provided i was able to implement it.

by: MuraliKanthPosted on 2009-09-23 at 18:15:58ID: 25409552

Thanks for your suggestions. I would definitely update my existing blog @scribblejava.wordpress.com.

by: Micheal_MalePosted on 2009-10-04 at 12:30:23ID: 25490439

Hi Murali. I have a question on this senario which you posted. Say for instance a user clicks OK to confirm for the session. For how long the session will be extended ?. It looks like it does not extend for 30 more minutes. It extends for 5 or 10 minutes. Thanks

by: Micheal_MalePosted on 2009-10-04 at 13:19:04ID: 25490722

For some reason when i do an alert in aler(userid) i get undefinied. Could you tell me why ?. It makes the call to the servlet and i can get the userid from the log statement but when i try to print on the JS function in sessionextend i get undefined for the userid.

Can you tell me what i am doing wrong murali ?

by: Micheal_MalePosted on 2009-10-04 at 17:31:53ID: 25491660

I found what the problem was.So when i press ok for the pop up message to extend the session before 5 min of expiring apparently it is suppose to ping my servlet and should refresh the session correct ?. However after clicking ok if i stay idle on the same page for a little 10 more min and click submit on the form i get a null pointer in my controller. In my controller i am getting the userid from session and It states that the userId which i am getting from the session is null ? could you tell me why is it doing that ?

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String user = (String)request.getSession(false).getAttribute("user");
		StringBuffer xml = new StringBuffer();
		xml.append("<?xml version=\"1.0\"?>\n");
		xml.append("<session userid=\"" + user + "\">\n");
 
		xml.append("</session>\n");
		response.setContentType("text/xml");
		response.getWriter().write(xml.toString());
		response.getWriter().flush();
	}

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Select all Open in new window

by: MuraliKanthPosted on 2009-10-04 at 18:44:55ID: 25491899

Hi Michael,

So when i press ok for the pop up message to extend the session before 5 min of expiring apparently it is suppose to ping my servlet and should refresh the session correct ?

>> Yes you are correct. But remember u cannot leave the alert for 5+ mins and then click on the "OK" to make the session extension. Because from the time it shows the alert it counts. So if you click on "OK" immediately after seeing the alert it should extend the session. By extension we mean the session-timeout reset.

could you tell me why is it doing that ?
>> could you make sure your session is still active before u get the userid from session in ur controller?.

by: Micheal_MalePosted on 2009-10-04 at 18:55:18ID: 25492049

Thank you Murali for your comments. So i clicked Ok before 5 min of my session expiring. And then i stay idle for 10 min and then when i click submit on my form my onBindAndValidate() method gets invoked. In that method i am getting the userId and couple of other stuff from the session. I added some log statements and then came to know that i receive a null pointer exception on :-

String user = (String)request.getSession(false).getAttribute("user");
log.info("user is " + user );

I get a null pointer on :-

String user = (String)request.getSession(false).getAttribute("user");

meaning that the session is not alive. What could be the problem ?. I can see that the PingSession servlet does get call when i click ok but session never gets extended.

by: Micheal_MalePosted on 2009-10-04 at 18:58:43ID: 25492059

I am sure i told you before that we don't have a session-timeout. however we do have a SessonListener which is set to default 30 min. I don't think that the listener is either a problem also.

by: MuraliKanthPosted on 2009-10-04 at 19:01:45ID: 25492068

Make sure the setTimeOut() has the timer value exactly 5 mins before session timeout.
Also ignore using false in getSession().

String user = (String)request.getSession().getAttribute("user");

Could you also add log statement to OnsessionDestroyed in your session listener, to check when ur session is destroyed?.

by: Micheal_MalePosted on 2009-10-04 at 19:24:27ID: 25492132

I don't think request.getSession(false) will make any difference. However i did put some logger statements in my listener on timing when the session is created and destroyed. Now i saw it created a session 2 min earlier and now monitoring to see when it will be destroyed. I will check in 30 min with that ajax implementation function also to see if my session gets expired earlier or not.

in setMaxInterval of listener i setted to 1800 which means 30 min. Will update in 30 min

by: MuraliKanthPosted on 2009-10-04 at 19:35:04ID: 25492159

You should set the timer to 25 mins and not 30 min. So every 25mins once it triggers the session extension.

by: Micheal_MalePosted on 2009-10-04 at 19:56:52ID: 25492221

I am sorry i did'nt get you murali ? In my JS i have set the timeout to :-

//25 min for prompt
setTimeout('promptUser()', 25 * 60 * 1000);

Now when i click ok in the pop up message i saw my servlet get called PingSession. I printed the userid and the XML does have the userId. But after 5 min of clicking OK in the pop up message i saw the log printed that the session is destroyed also. Why the session got destroyed in the listener when i did ping the servlet through the AJAX function also ?

by: MuraliKanthPosted on 2009-10-04 at 21:02:49ID: 25492406

It looks really wierd. Did you try just by letting the application be idle for <30 mins and before it reaches 30 mins to click on somelink and see if it still expires the session. I would recommend you to set the session timeout in web.xml to 30 mins and then try this out.

by: Micheal_MalePosted on 2009-10-04 at 21:09:17ID: 25492421

hmm sounds like a good idea of setting the session timeout in web.xml. I will let you know. BTW thanks for your help murali. I will keep you updated. If you want i can create a seperate thread to give you some points in debugging with me.

by: MuraliKanthPosted on 2009-10-04 at 21:29:40ID: 25492468

I would be glad to help you in debugging this problem. Its up to you to create a seperate thread.

20120131-EE-VQP-002

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spring framework

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Spring

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