public class SignonInterceptor extends HandlerInterceptorAdapter {

  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
      throws Exception {

    UserSession userSession = (UserSession) WebUtils.getSessionAttribute(request, "userSession");
    if (userSession == null) {
      String url = request.getServletPath();
      String query = request.getQueryString();
      ModelAndView modelAndView = new ModelAndView("SignonForm", "message", "You must be signed on to access this page.");
      if (query != null) {
        modelAndView.addObject("signonForwardAction", url + "?" + query);
      } else {
        modelAndView.addObject("signonForwardAction", url);
      }
      throw new ModelAndViewDefiningException(modelAndView);
    }

    return true;
  }
}