for retreiving the value from session.

String uname = (String)session.getAttribute(”username”);

…besides not having any info to store

Not having anything to store would be the main point here. As in, when the jsps are simple, open, accessible by all, pages, we should make sure, that no session is automatically created, if not needed.

Now, there are perfectly good reasons to keep session on the server. There are also reasons not to. But this would be another post. When I mention a “..share-nothing stateless architecture on the server-side..”, it is a solution to scaling bigtime, for large, heavy load sites. You could keep session state at the client then, or keep it in the database.

This is worth creating an issue for the Jasper team.

Hmm, coming to think about it, I do not think so

I guess the implementation of Jasper, which simply creates a session up front when @page session="true" (or the default) is present, looks like a (good) trade-off in the compiler implementation (to me).

Let’s think about what it would take, to create the session on demand… Given the JSP code below:


<% if (something) {
session.setAttribute(...); // use session here
} else {
// code that does NOT use session here
}
%>


To have Jasper create a servlet, that only obtains a session, when (if) the code, in execution, actually reaches the block of code which use the session, Jasper would have to be a full blown Java compiler. It would have to parse scriptlet syntax, and determine type of session variable access, and ADD EXTRA CODE THERE, which obtained the session.

Would it not?

I think, with the knowledge on how Jasper forces early session creation, I can work-around it. I would simply extract the block of code, that use the session, into another JSP, and then have the main jsp file have session="false". I would then dynamically include the other JSP, which uses a session.

Despite I’m adding a @page session=”false” directive in the JSPs, Tomcat is still reporting it has an active session (seeing it throw the Tomcat Manager).

Regarding to the compile error, I found that as a workaround you could check the value of pageContext.getSession() which will return the session if it exists, or null if it doesn’t.