session过期后没法跳转页面 如果按f5的话可以跳转到登陆页面

protected void doFilterInternal(HttpServletRequest request,
			HttpServletResponse response, FilterChain filterchain)
			throws ServletException, IOException {
		
		
	
		 // 不过滤的uri  
        String[] notFilter = new String[] { "login.jsp","login","plui","include",".css","testLoginServlet" };  
  
        // 请求的uri  
        String uri = request.getRequestURI();
  
        // uri中包含plattutor3时才进行过滤  
        if (uri.indexOf("plattutor3") != -1) {  
        	
            // 是否过滤  
            boolean doFilter = true;  
            for (String s : notFilter) {  
                if (uri.indexOf(s) != -1) {  
                	
                    // 如果uri中包含不过滤的uri，则不进行过滤  
                	System.out.println("session filter  不过滤__________");
                    doFilter = false;  
                    break;  
                }  
            }  
            if (doFilter) {  
	            if(request.getSession(false)==null){ 
	      			  
	    				System.out.println("session已经过期"); 
	    				response.sendRedirect("/plattutor3/tutor/test/login.jsp");
	    				
	    				
	    		}else{
	                // 执行过滤  
	                // 从session中获取登录者实体  
		              Object obj=  request.getSession(false).getAttribute("userInfo");  
		                if (null == obj) {  
		                	System.out.println(request.getSession(false)+"session filter__________");
		                    // 如果session中不存在登录者实体，则弹出框提示重新登录  
		                    // 设置request和response的字符集，防止乱码  
		                   // request.setCharacterEncoding("UTF-8");  
		                    //response.setCharacterEncoding("UTF-8");  
		                    //PrintWriter out = response.getWriter();  
		                    String loginPage = "/plattutor3/tutor/test/login.jsp";  
		                    response.sendRedirect(loginPage);
		                    request.getRequestDispatcher(loginPage).forward(request, response);
		                } else {  
		                    // 如果session中存在登录者实体，则继续  
		                	filterchain.doFilter(request, response);  
		                }  
	    		}
            } else {