Under what conditions is a JSESSIONID created?

Question

Hi,

When / what are the conditions when a JSESSIOINID is created?

Is it per a domain? For instance, if I have a Tomcat app server, and I deploy multiple web applications, will a different JSESSIONID be created per context (web application), or is it shared across web applications as long as they are the same domain?

Answer 1

CORRECTION: Please vote for Peter Štibraný's answer - it is more correct and complete!

A "JSESSIONID" is the unique id of the http session - see the javadoc here. In the javadoc you will find the following sentence: "Session information is scoped only to the current web application (ServletContext), so information stored in one context will not be directly visible in another."

So when you first hit a site, a new session is created and bound to the SevletContext. If you deploy multiple applications, the session is not shared.

You can also invalidate the current session and therefore create a new one. e.g. when switching from http to https (after login), it is a very good idea, to create a new session.

Hope, this answers your question.

Answer 2

JSESSIONID cookie is created/sent when session is created. Session is created when your code calls request.getSession() or request.getSession(true) for the first time. If you just want get session, but not create it if it doesn't exists, use request.getSession(false) -- this will return you a session or null. In this case, new session is not created, and JSESSIONID cookie is not sent. (This also means that session isn't necessarily created on first request... you and your code is in control when the session is created)

Sessions are per-context:

SRV.7.3 Session Scope

HttpSession objects must be scoped at the application (or servlet context) level. The underlying mechanism, such as the cookie used to establish the session, can be the same for different contexts, but the object referenced, including the attributes in that object, must never be shared between contexts by the container.

(Servlet 2.4 specification)

Update: Every call to JSP page implicitly creates new session if there is no session yet. This can be turned off by session='false' page directive, in which case session variable is not available on JSP page at all.

Answer 3

See http://java.sun.com/j2ee/1.4/docs/tutorial/doc/Servlets11.html#wp64744

Answer 4

Here is some information about one more source of the JSESSIONID cookie:

I was just debugging some Java code that runs on a tomcat server. I was not calling request.getSession() explicitly anywhere in my code but I noticed that a JSESSIONID cookie was still being set.

I finally took a look at the generated Java code corresponding to a JSP in the work directory under Tomcat.

It appears that, whether you like it or not, if you invoke a JSP from a servlet, JSESSIONID will get created!

Added: I just found that by adding the following JSP directive:

<%@ page session="false" %>

you can disable the setting of JSESSIONID by a JSP.

Answer 5

For links generated in a JSP with custom tags, I had to use

<%@ page session="false" %>

in the JSP

AND

request.getSession().invalidate();

in the Struts action