invalidate the session in servlet and redirect the user to he same url, making normal processes to kick in.

gistfile1.java

                    // invalidate the session
                    session.invalidate();

                    // redirect the user to where they were, so normal login process can kick in
                    HttpServletResponse response = (HttpServletResponse) servletResponse;
                    HttpServletRequest request = (HttpServletRequest) servletRequest;
                    StringBuffer requestUrl = request.getRequestURL();

                    // by default all GET params from query string will be missing from getRequestURL, let's reconstruct it
                    if (request.getQueryString() != null) {
                        requestUrl.append("?").append(request.getQueryString());
                    }
                    response.sendRedirect(requestUrl.toString());
                    return;