本文详细介绍了JSP内置对象的功能和使用方法，包括out、request、response等对象的应用场景，并对比了请求转发与请求重定向的区别，同时深入探讨了session和application对象在会话管理和全局数据共享中的作用。
一、JSP内置对象简介
Web容器创建的一组对象，不使用new关键字就可以使用的内置对象。
- out
- request
- response
- session
- application
- Page pageContext exception config
二、out对象
三、提交表单的方式
login.jsp :
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>My JSP 'login.jsp' starting page</title>
</head>
<body>
<h1>用户登录</h1>
<hr>
<form action="dologin.jsp" name="loginForm" method="post">
<table>
<tr>
<td>用户名：</td>
<td><input type="text" name="username"/></td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password" name="password"/></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登录"></td>
</tr>
</table>
</form>
</body>
</html>dologin.jsp :
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
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 'dologin.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>登录成功</h1>
<hr>
</body>
</html>四、request对象
reg.jsp :
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
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 'index.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>用户注册</h1>
<hr>
<%
int number=-1;
//说明用户第一次访问页面，计数器对象还未创建
if(application.getAttribute("counter")==null)
{
application.setAttribute("counter", 0);
}
number = Integer.parseInt(application.getAttribute("counter").toString());
number++;
application.setAttribute("counter", number);
%>
<!-- <form name="regForm" action="request.jsp" method="post"> -->
<form name="regForm" action="response.jsp" method="post">
<table>
<tr>
<td>用户名：</td>
<td><input type="text" name="username"/></td>
</tr>
<tr>
<td>爱好：</td>
<td>
<input type="checkbox" name="favorite" value="read">读书
<input type="checkbox" name="favorite" value="music">音乐
<input type="checkbox" name="favorite" value="movie">电影
<input type="checkbox" name="favorite" value="internet">上网
</td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="提交"/></td>
</tr>
</table>
</form>
<br>
<br>
<a href="request.jsp?username=李四">测试URL传参数</a>
<br>
<br>
<center>
您是第<%=number %>位访问本页面的用户。
</center>
</body>
</html>
request.jsp :
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
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 'index.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>request内置对象</h1>
<%
request.setCharacterEncoding("utf-8"); //解决中文乱码问题，无法解决URL传递中文出现的乱码问题。
// 解决URL传递中文出现的乱码: 在server.xml中的Connector标签下设置URIEncoding="utf-8"
request.setAttribute("password", "123456");
%>
用户名：<%=request.getParameter("username") %><br>
爱好 ：<%
if(request.getParameterValues("favorite")!=null)
{
String[] favorites = request.getParameterValues("favorite");
for(int i=0;i<favorites.length;i++)
{
out.println(favorites[i]+" ");
}
}
%> <br>
密码：<%=request.getAttribute("password") %><br>
请求体的MIME类型:<%=request.getContentType() %><br>
协议类型及版本号: <%=request.getProtocol() %><br>
服务器主机名 :<%=request.getServerName() %><br>
服务器端口号：<%=request.getServerPort() %><BR>
请求文件的长度 ：<%=request.getContentLength() %><BR>
请求客户端的IP地址：<%=request.getRemoteAddr() %><BR>
请求的真实路径：<%=request.getRealPath("request.jsp") %><br>
请求的上下文路径：<%=request.getContextPath() %><BR>
</body>
</html>
五、response对象
response.jsp :
<%@ page language="java" import="java.util.*,java.io.*" contentType="text/html; charset=utf-8"%>
<%
response.setContentType("text/html;charset=utf-8"); //设置响应的MIMI类型
out.println("<h1>response内置对象</h1>");
out.println("<hr>");
//out.flush();
PrintWriter outer = response.getWriter(); //获得输出流对象
outer.println("大家好，我是response对象生成的输出流outer对象"); //如果不用out.flush(),那么PrintWriter输出的结果总是提前于内置对象的输出
// response.sendRedirect("reg.jsp");//请求重定向
//请求重定向
//response.sendRedirect("request.jsp");
//请求转发
request.getRequestDispatcher("request.jsp").forward(request, response);
%>六、请求转发与请求重定向
请求重定向是客户器端行为而请求转发是服务器端行为
七、session对象
session_page1.jsp :
<%@ page language="java" import="java.util.*,java.text.*" contentType="text/html; charset=utf-8"%>
<%
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 'index.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>session内置对象</h1>
<hr>
<%
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
Date d = new Date(session.getCreationTime());
session.setAttribute("username", "admin");
session.setAttribute("password", "123456");
session.setAttribute("age", 20);
//设置当前session最大生成期限单位是秒
//session.setMaxInactiveInterval(10);//10秒钟
%>
Session创建时间：<%=sdf.format(d)%><br>
Session的ID编号：<%=session.getId()%><BR>
从Session中获取用户名：<%=session.getAttribute("username") %><br>
<%--target="_blank"表示打开新窗口--%>
<a href="session_page2.jsp" target="_blank">跳转到Session_page2.jsp</a>
</body>
</html>
session_page2.jsp :
<%@ page language="java" import="java.util.*,java.text.*" contentType="text/html; charset=utf-8"%>
<%
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 'index.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>session内置对象</h1>
<hr>
<%
//SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
//Date d = new Date(session.getCreationTime());
//session.setAttribute("username", "admin");
%>
Session的ID编号：<%=session.getId()%><BR>
从Session中获取用户名：<%=session.getAttribute("username") %><br>
Session中保存的属性有:<%
String[] names =session.getValueNames();
for(int i=0;i<names.length;i++)
{
out.println(names[i]+" ");
}
%> <br>
</body>
</html>
浏览器不关闭，服务器就会保存用户sessions状态，多个页面可属于同一个session会话。
会话保存在服务器的内存里，保存着不同的用户的session。
本次会话的所有页面都关闭后再重新访问某个JSP或者Servlet将会创建新的会话
八、application对象
相当于静态变量（全局）
setAttribute方法参数第一个为字符串，第二个参数为需要保存的对象
使用application 实现计数器效果，在application中保存整型变量num，setAttribute(”counter”,num);
九、page对象
当前page页面对象的字符串描述：<%=page.toString() %><br>结果：
当前page页面对象的字符串描述：org.apache.jsp.page_jsp@32ac7d17十、pageContext对象和config对象
forward使当前页面跳转到另一个页面，地址栏不会放生变化，有点类似于请求转发。
十一、exception对象
errorPage: 指定异常页面，当发生异常时交由其处理
isErrorPage：设置该页面为处理异常的页面
当异常发生时，会跳转到异常处理页面，地址栏不会发生变化，相当于请求转发。
exception_test.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 'index.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>测试异常的页面</h1>
<hr>
<%
System.out.println(100/0); //抛出运行时异常，算数异常
%>
</body>
</html>
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 'index.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>
<hr>
异常的消息是：<%=exception.getMessage()%><BR>
异常的字符串描述：<%=exception.toString()%><br>
</body>
</html>
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