1. JSP的内置对象有
request，请求对象，代表来自客户端的请求
response， 响应对象，代表对客户端的响应
out，输出对象，通过out对象发送的内容将是浏览器需要显示的内容。
application 应用程序对象，负责提供应用程序在服务器中运行时提供的一些全局信息。
config 配置对象
page 页面对象
exception 异常对象
pageContext 页面上下午对象
session 会画对象， 代表服务器与客户端所建立的会话，当需要保存在不同的JSP页面中保留客户信息的情况下使用，比如在线购物、客户轨迹跟踪等。
2. request，out对象的使用
创建login.jsp, result.jsp
login.jsp
<%@ 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>
<form action="result.jsp" method="post">
username: <input type="text" name="username1"><br>
password: <input type="password" name="password1"><br>
<input type="submit" value="submit" >
<input type="reset" value="reset" >
</form>
</body>
</html>
result.jsp
<%@ 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>
<%
String username = request.getParameter("username1");
String password = request.getParameter("password1");
out.println("username:" + username + "<br>");
out.println("password:" + password + "<br>");
System.out.println("username:" + username );
System.out.println("password:" + password );
%>
</body>
</html>
result.jsp 使用了request和out对象。
3. session对象的使用
session1.jsp
<%@ 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>
<form action="session2.jsp">
姓名
<input type="text" name="username">
<input type="submit" value="提交">
</form>
</body>
</html>
session2.jsp
<%@ 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>
<%
String username = request.getParameter("username");
session.setAttribute("LogName", username);
%>
你的名字是 <%=username %>已經写入session
<br>
<a href='session3.jsp'>check</a>
</body>
</html>
session3.jsp
<%@ 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>
session值为：
<% String yourname = (String)session.getAttribute("LogName");
if(yourname == null) {
%>
您还未登录
<% } else { %>
"<%=yourname %>"已经登录
<%} %>
</body>
</html>