public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
            HttpServletResponse hsr = (HttpServletResponse) res;
            HttpServletRequest hreq = (HttpServletRequest) req;

                HttpSession session = hreq.getSession(false);

                if(session == null) {
                    hsr.sendRedirect("/prj1/sessionexpiry");
                    return;
                } else {
                    chain.doFilter(req, res);
                }

        }