项目后台判断session过期的页面代码

<%@page import="com.bn.car.core.Constants"%>
<%@page import="com.bn.car.biz.sysadmin.dto.SysAdminInfoDTO"%>
<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>

<%

    SysAdminInfoDTO dto = (SysAdminInfoDTO)session.getAttribute("sysAdminInfoDto");
    // ////ln("include page println....");
    if(dto == null){ 
            %>
            <script type="text/javascript">
                window.parent.location.href="<%=Constants.ROOT%>property/index.jsp";
                alert("非法访问!!请登录后台系统!!");
            </script>
            <%
            return;
    }
%>

<jsp:include page="include/checksession.jsp" ></jsp:include>