excepton对象是一个异常对象，当一个页面在运行过程中发生了异常，就产生了这个对象，如果一个jsp页面要应用此对象，就必须把isErrorPage设置为true，否则无法编译。它实际上是java.lang.Throwable的对象，常用方法：
String getMessage()返回描述异常的消息
String toString()反水关于异常的简短描述信息
void printStackTrace()显示异常及其栈轨迹
Throwable FillInStackTrace()重写异常的执行栈轨迹
使用：在实际中有时候会出现异常，可以专门写一个jsp来处理
抛出异常的jsp
<%@ page language="java" import="java.util.*"
contentType="text/html; charset=utf-8" errorPage="exception.jsp"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>My JSP 'login.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
--> </head> <body>
<h1>抛出异常页面</h1>
<%
System.out.println(100/0);
%>
</body>
</html>
需要在page头那里添加处理异常的jsp，即errorPage="exception.jsp"
exception.jsp
<%@ page language="java" import="java.util.*"
contentType="text/html; charset=utf-8" isErrorPage="true"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>"> <title>My JSP 'login.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
--> </head> <body>
<h1>exception内置对象</h1>
异常消息为：<%=exception.getMessage() %><br>
异常的字符串描述：<%=exception.toString() %>
</body>
</html>
需要在头部添加
isErrorPage="true" 运行的结果
