Java EE (Java Enterprise Edition) General Discussion

Hi,

I'm using a servlet in my jsf-based application to retrieve some data via an xml request.
The FacesContext is set in the servlet as proposed in http://www.thoughtsabout.net/blog/archives/000033.html.
I have some important parameters set in the http session so when getting the servlet context I do:

servletContext = ((HttpServletRequest)request).getSession(false).getServletContext();

The problem is that sometimes ((HttpServletRequest)request).getSession(false) returns null. I can't recreate the session because I will lose all parameters set.
Can anybody tell me why is the http session lost or why does it become irrecovarable?

Thanks