页面捕捉容器抛出的异常. 系统 500 页面

<%@ page contentType="text/html;charset=UTF-8" isErrorPage="true" %>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page import="org.apache.log4j.Logger" %>
<link rel="stylesheet"  type="text/css" href="/css/index.css"></link>
<%
        Throwable ex = null;
        if (exception != null)
	         ex = exception;
        if (request.getAttribute("javax.servlet.error.exception") != null)
	          ex = (Throwable) request.getAttribute("javax.servlet.error.exception");

        Logger logger = Logger.getLogger("500.jsp");
        logger.error(ex.getMessage(), ex);

%>