Java EE (Java Enterprise Edition) General Discussion

Hello!
I'd be very pleased if you could help me.
My application uses session.getAttribute() and session.setAttibute(). It works properly on my local (developer's) computer. When I transfer my project into remote server session attribute doesn't work. getAttribute() returns null. Both machines work on Windows platform, Tomcat 6. Here is my code:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	String par = request.getParameter("lang");
	if (par != "")
	{
		HttpSession session = request.getSession(true);
		session.setAttribute("language", par);
	}
	response.sendRedirect(request.getHeader("referer"));
}

HttpSession session = request.getSession(true);
if (session.getAttribute("language") != null)
{
	Locale l = new Locale((String) session.getAttribute("language"));
	String lang = l.getISO3Language();
        String file = sc.getRealPath(uri + "index-" + lang + ".jsp");
        if (log.isDebugEnabled()) {
    	      log.debug("Trying: " + file);
        }
        File f = new File(file);
        if (f.exists()) {
    	      return uri + "index-" + lang + ".jsp";
        }
}

I'd like you to advise me what I should change to make it work. May be any settings in server.xml, context.xml? Cookies?
Thanks in advance.

Best regards,
Pavel