jsp filter过滤request数据的问题

Question

我的需求是:
当页面session失效后如果再进行请求,则跳转到登陆页面,代码如下:

 @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain fc)
            throws IOException, ServletException {
        // TODO Auto-generated method stub
        User user=(User) ((HttpServletRequest)request).getSession().getAttribute("loginUser");
        if (null==user) {
            if (request.getParameter("userCode")!=null) {
                fc.doFilter(request, response);
            }else {
                request.getRequestDispatcher("admin/userLogin.jsp").forward(request, response);
                return;
            }
        }
    }

现在所有请求都没有返回值了,页面一片空白,就是第一次登录页面完全没显示

Answer 1

将代码改下

 User user=(User) ((HttpServletRequest)request).getSession().getAttribute("loginUser");
        if (null==user && request.getParameter("userCode")==null) {
            request.getRequestDispatcher("admin/userLogin.jsp").forward(request, response);
            return;
        }
        fc.doFilter(request, response);

你针对的是request. 如果 web.xml配置里面的filter 拦截forward 要去掉

 <filter-mapping>
        <filter-name>SessionFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher>
        <dispatcher>FORWARD</dispatcher>  将这行去掉
    </filter-mapping>