How to check for session in JSP EL?

Question

How do you check if a session exists for the request in EL? I'm trying something like:

<c:if test="${pageContext.request.session != null}"> ... </c:if>

but it seems like it's never null.

Carrel

Answer 1

It's indeed never null. The session is always present in JSP EL, unless you add

<%@page session="false" %>

to top of JSP. You could then check for the session as follows (EL 2.2 only!):

<c:if test="${pageContext.request.getSession(false) != null}">
    <p>The session has been created before.</p>
</c:if>

I'm not sure what's the concrete functional requirement is. If you'd like to check if the session is new or has already been created, use HttpSession#isNew() instead.

<c:if test="${not pageContext.session['new']}">
    <p>You've already visited this site before.</p>
</c:if>
<c:if test="${pageContext.session['new']}">
    <p>You've just started the session with this request!</p>
</c:if>

(the brace notations for new are mandatory because new is a reserved literal in Java language)

Of if you're relying on a specific session attribute, such as the logged-in user which is been set as

session.setAttribute("user", user);

then you should rather be intercepting on that instead:

<c:if test="${not empty user}">
    <p>You're still logged in.</p>
</c:if>
<c:if test="${empty user}">
    <p>You're not logged in!</p>
</c:if>

Salmanazar

You're too good, answering a question I didn't even ask. Checking for the user was what I wanted. – Carrel

You're welcome. Questions which makes no sense in real world code have often a completely different functional requirement behind. Then I often guess for the most common functional requirements which look much like whatever you really need to achieve. You would save me (and others) time if you just state that in your future questions ;) – Salmanazar

It's sometimes easy to get caught up in a coding storm and forget to take a step back and realize the approach is wrong altogether. Thanks again. – Carrel

Answer 2

Seems to works with:

<c:if test="${fn:length(sessionScope) > 0}">

I wonder if there's a better way, since this requires that I have session attributes (I always do, but it's not really clean)?

Carrel

Answer 3

In J2EE there will always be a session object when a user visits a site.

What is a Session ? A session is pretty much what it sounds, when a user makes a page request to the server, the server creates a temporary session to identify that user. So when that same user goes to another page on that site, the server identifies that user. So a session is a small and temporary unique connection between a server and the user enabling it to identify that user across multiple page requests or visits to that site.

So basically if your hitting a page you have a session because your using JSP, which eventually gets converted to servlets.

http://www.stardeveloper.com/articles/display.html?article=2001062001&page=1

Felicitation