// 全局Ajax设置, 用于session过期后的跳转

 function ajaxSetup() {

     $.ajaxSetup({

         timeout : 10000,

         beforeSend : function(xhr) {

             //添加ajax请求标识

             xhr.setRequestHeader("ajaxReq", "ajax");

         },

         complete : function(xhr, ts) {

             if (xhr.statusText == 'sessiontimeout' && xhr.status == 403) {

                 // 跳转

                 window.location.href = "login.jsp";

             }

         }

     });

 }

 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

         HttpServletRequest req = (HttpServletRequest) request;

         HttpServletResponse res = (HttpServletResponse) response;

         String servletPath = req.getServletPath();

         if(except.contains(req.getRequestURI())){

             chain.doFilter(request, response);

         }

         Object sessionObj = req.getSession().getAttribute(key);

         if(sessionObj==null){

             //如果是ajax请求

             if(req.getHeader("ajaxReq")!=null && req.getHeader("ajaxReq").equals("ajax")){

                 res.setHeader("sessionState", "timeout");

                 res.setStatus(403);

                 return;

             }else{

                 chain.doFilter(request, response);

                 String contextPath = req.getContextPath();

                 String redirect = servletPath + "?" + StringUtils.defaultString(req.getQueryString());

                 res.sendRedirect(contextPath + forward + "?redirect=" + URLEncoder.encode(redirect, "UTF-8"));

             }

         }else{

             // pass the request along the filter chain

             chain.doFilter(request, response);

             System.out.println("chain.do after");

         }

     }