jsp内置对象（4）：response，out，pagecontext
一：response对象
1.定时刷新
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'responseDemo1.jsp' starting page</title>
</head>
<body>
<%!
//定义一个全局变量
int count=0;
%>
<%
response.setHeader("refresh","2");
%>
<h3>刷新了<%=count++ %>次！</h3>
</body>
</html>
2.设置Cookie
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'responseDemo2.jsp' starting page</title>
</head>
<body>
<%
//创建cookie
Cookie ck1=new Cookie("aa","Spring");
Cookie ck2=new Cookie("bb","Summer");
//设置保存时间
ck1.setMaxAge(60);
ck2.setMaxAge(60);
//添加cookie
response.addCookie(ck1);
response.addCookie(ck2);
%>
</body>
</html>
3.获取cookie
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'responseDemo1.jsp' starting page</title>
</head>
<body>
<%
//取出Cookie
Cookie c[]=request.getCookies();
for(int i=0;i<c.length;i++){
%>
<h3><%=c[i].getName() %>--><%=c[i].getValue() %></h3>
<%
}
%>
</body>
</html>
二：out对象
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'init.jsp' starting page</title>
</head>
<body>
<%
int buffer=out.getBufferSize();
int avaliable=out.getRemaining();
int use=buffer-avaliable;
%>
缓冲区大小：<%=buffer %><br>
未使用的大小：<%=avaliable %><br>
使用的大小：<%=use %>
</body>
</html>
三：pageContext对象
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'pageContext.jsp' starting page</title>
</head>
<body>
<%
//页面跳转
pageContext.forward("Demo2.jsp?info=spring");
%>
</body>
</html>
Demo2.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'Demo2.jsp' starting page</title>
</head>
<body>
<%
String info=pageContext.getRequest().getParameter("info");
%>
<h3>info=<%=info %></h3>
<h3>realPath=<%=pageContext.getServletContext().getRealPath("/") %></h3>
</body>
</html>
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