protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=utf-8");
        HttpSession session = request.getSession();
        User user = (User)session.getAttribute("fgzb_user");
        if(user != null) {
            session.setAttribute("fgzb_user",null);
        }
        session.invalidate();
        boolean fromLoginFilter = Boolean.valueOf(request.getParameter("fromLoginFilter"));
        StringBuffer sb = new StringBuffer("<script>");
        String logoutUrl = request.getContextPath()+"/login.jsp";
        if(fromLoginFilter) {
            sb.append("alert('用户身份已经过期，请重新登录。');");
        }
        sb.append("top.location.href='").append(logoutUrl).append("'</script>");
        PrintWriter pw = response.getWriter();
        pw.print(sb.toString());
    }