page：当前页面，也就是只要跳到别的页面就失效了
request：一次会话，简单的理解就是一次请求范围内有效
session：浏览器进程，只要当前页面没有被关闭（没有被程序强制清除），不管怎么跳转都是有效的
application：服务器，只要服务器没有重启（没有被程序强制清除），数据就有效
PageContext作用域：
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/lose.dtd"> <html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<title>Hello</title>
</head>
<body>
<%
pageContext.setAttribute("name", "fuckyou");
pageContext.setAttribute("fuckyou", 101010);
%> <%
String name = (String)pageContext.getAttribute("name");
int fuckyou = (Integer)pageContext.getAttribute("fuckyou");
%> <font> name:<%=name %> fuckyou:<%=fuckyou %>
</font>
<br>
<font> name:<%=name %> fuckyou:<%=fuckyou %>
</font> </body>
</html>
Request作用域：
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
// 设置两个request范围的数据 key-> value
request.setAttribute("fuckyou","this fuckyou is coming from here");
request.setAttribute("fuckfuckyou",01010);
%>
<jsp:forward page="requestTarget.jsp"></jsp:forward>
</body>
</html>
//接收：
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<%@ page import="java.util.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
<span style="white-space:pre"> </span>// 取值
<span style="white-space:pre"> </span>String fuck=(String)request.getAttribute("fuckyou");
<span style="white-space:pre"> </span>int you=(Integer)request.getAttribute("fuckfuckyou");
<span style="white-space:pre"> </span>
<span style="white-space:pre"> </span>// 获取头信息
<span style="white-space:pre"> </span>Enumeration enu=request.getHeaderNames();
<span style="white-space:pre"> </span>while(enu.hasMoreElements()){
<span style="white-space:pre"> </span>String headerName=(String)enu.nextElement();
<span style="white-space:pre"> </span>String headerValue=request.getHeader(headerName);
%>
<span style="white-space:pre"> </span><h4><%=headerName %> <%=headerValue %></h4>
<%
<span style="white-space:pre"> </span>}
<span style="white-space:pre"> </span>
%>
<font>姓名：<%=fuck %></font>
<font>年龄：<%=you %></font>
</body>
</html>
session作用域：
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
// 设置两个session范围的数据 key-> value
session.setAttribute("fuck","you");
session.setAttribute("fuckyou",01010);
%>
<h1>session作用域！</h1>
</body>
</html>
//接收
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
<span style="white-space:pre"> </span>// 取值
<span style="white-space:pre"> </span>String fuck=(String)session.getAttribute("fuck");
<span style="white-space:pre"> </span>int fuckyou=(Integer)session.getAttribute("fuckyou");
%>
<font>hello<%=fuck %></font>
<font>world<%=fuckyou %></font>
</body>
</html>
application作用域：
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
// 设置两个application范围的数据 key-> value
application.setAttribute("name","fuck");
application.setAttribute("fuckyou",01010);
%>
<h1>application作用域</h1>
</body>
</html>
//接收
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<%
<span style="white-space:pre"> </span>// 取值
<span style="white-space:pre"> </span>String fuck=(String)application.getAttribute("name");
<span style="white-space:pre"> </span>int you=(Integer)application.getAttribute("fuckyou");
%>
<font>fuck<%=fuck %></font>
<font>you<%=you %></font>
</body>
</html>