dofilter拦截后反复跳转

Glensea

已于 2022-09-18 16:30:55 修改

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分类专栏： bug解决文章标签： java servlet 前端

于 2022-09-18 16:29:30 首次发布

本文链接：https://blog.youkuaiyun.com/sparkstark/article/details/126919107

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问题代码：

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) servletRequest;
        HttpServletResponse resp = (HttpServletResponse) servletResponse;

        String servletPath = req.getServletPath();
        System.out.println("servletPath = " + servletPath); // 测试是否是路径问题
        if ("/templates/login.jsp".equals(servletPath)) {
            System.out.println(1); // 测试是否是路径问题
            filterChain.doFilter(servletRequest, servletResponse);
        }
        // 放行静态资源  .css  .js  .jpg
        if (servletPath.startsWith("/static")){
            //放行请求
            filterChain.doFilter(servletRequest, servletResponse);
        }

        String method = req.getParameter("method");
        if ("getCaptcha".equals(method)) {
            filterChain.doFilter(servletRequest, servletResponse);
        }
        if ("login".equals(method)) {
            filterChain.doFilter(servletRequest, servletResponse);
        }

        // 用户登录后放行
        HttpSession session = req.getSession();
        Object user = session.getAttribute("user");
        if (user != null) {
            filterChain.doFilter(servletRequest, servletResponse);
        }

        //重定向到登录页  非法用户
        resp.sendRedirect(req.getContextPath() + "/templates/login.jsp");
    }

运行结果

servletPath = /templates/login.jsp
1
servletPath = /templates/login.jsp
1
servletPath = /templates/login.jsp
1
servletPath = /templates/login.jsp
1
... ...

问题原因：
重定向后由于if ("/templates/login.jsp".equals(servletPath))执行后继续向下执行，再次来到resp.sendRedirect(req.getContextPath() + "/templates/login.jsp");进行重定向进入，导致进入反复跳转的死循环。

解决方法
在每个filterChain.doFilter(servletRequest, servletResponse);放行后加上return;，中断程序。
正确代码如下：

 @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) servletRequest;
        HttpServletResponse resp = (HttpServletResponse) servletResponse;

        String servletPath = req.getServletPath();
        if ("/templates/login.jsp".equals(servletPath)) {
            filterChain.doFilter(servletRequest, servletResponse);
            return;
        }
        // 放行静态资源  .css  .js  .jpg
        if (servletPath.startsWith("/static")){
            //放行请求
            filterChain.doFilter(servletRequest, servletResponse);
            return;
        }

        String method = req.getParameter("method");
        if ("getCaptcha".equals(method)) {
            filterChain.doFilter(servletRequest, servletResponse);
            return;
        }
        if ("login".equals(method)) {
            filterChain.doFilter(servletRequest, servletResponse);
            return;
        }

        // 用户登录后放行
        HttpSession session = req.getSession();
        Object user = session.getAttribute("user");
        if (user != null) {
            filterChain.doFilter(servletRequest, servletResponse);
            return;
        }

        //重定向到登录页  非法用户
        resp.sendRedirect(req.getContextPath() + "/templates/login.jsp");
    }