Checking session

[shaf maff]

Hi Guys

What is the best way to check if a session exists in a jsp using jstl ?

[Sidd Kulk]

I believe that using JSTL(or EL) one can access the variables in session or request scope.
And a session would always be associated with a JSP(or any Request, for that matter). I assume that what you want to check is existence of a variable in session scope. That can be done using EL.

Cheers,
Sid

[Sagar Rohankar]

By default, each JSP page has valid session object exits, because of page directive.
But If you make it false, then with JSTL we can do something like this,

 
<c:if test="${sessionScope == null}"> 
  ...
</c:if> 
   

I might be wrong here, please correct me If so

[Seetharaman Venkatasamy]

Sagar Rohankar wrote:

 
<c:if test="${sessionScope == null}"> 
  ...
</c:if> 
   

I might be wrong here, please correct me If so

Think of this ${sessionScope == null} ?

[Sagar Rohankar]

seetharaman venkatasamy wrote:

Think of this ${sessionScope == null} ?

Hmm, After looking at JSP docs, I found that "sessionScope" and "seesion" are different object, first one is Map whereas later one is actual session object,

So I got a session object,

${pageContext.session}

Now , question arises about how to check session existence, thus I checked its nullabilty, like

session is null : ${pageContext.session == null}

But, it didn't worked out, because 'null' is a literal and not an object

So I found something new, which is valid for any object/values, empty operator,
So finally it works !!,

Session is null : ${empty pageContext.session}

Is it correct ?

[shaf maff]

None of the suggestions work.

[Bear Bibeault]

What are you actually trying to accomplish?

[shaf maff]

I want to make sure a session exists on my page, if it doesnt the user is redirected to the login page.

[Bear Bibeault]

But why? Checking for the session itself is really, really weird.

Are you just trying to find out if someone is logged in or not? That's usually done by checking for specific scoped variables in the session, not the session itself.

[shaf maff]

Ok, thanks for enlightening me. So if I have the following var in my session:

session = request.getSession(true);
session.setAttribute("userid", user.getId());

How would I check it in a jsp file ?

[Bear Bibeault]

Personally, I would do this in a filter so that you don;t have to check in each and every JSP (and are you not using page controllers?)

But tio check for the existence of a scoped variable in session scope:

<c:if test="${empty sessionScope.whatever}">    

[shaf maff]

Thanks. I am using controllers for all my pages except for the index (its an ajax app). What is a filter ?

[Bear Bibeault]

If you have page controllers, why would you be waiting until you get to the JSP to perform this kind of check?

Servlet filter

[shaf maff]

Ok, I looked into the filter and it looks very promising, I am planning on scrapping my current layout and use filters instead, but us newbies get out of one hole only to fall into another. Having said that, here is a thread I could use your assistance on: https://coderanch.com/t/434266/Servlets/java/Filter#1929582