JSP中四种属性保存范围(2)

1.session

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             //获取session ID  Manager 可以将session保存在本地上
             String id = session.getId();
         %>
         <h1><%=id %></h1>
     </body>
 </html>

 <%@ page language="java" contentType="text/html"
     pageEncoding="GBK"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <title>Insert title here</title>
 </head>
 <body>
     <%
         if(session.isNew()){
     %>
         <h1>欢迎新用户</h1>
     <%
         }else{
     %>
             <h1>老用户</h1>
         <%
         }
     %>
 </body>
 </html>

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             long start = session.getCreationTime(); //创建此会话的时间
             long end = session.getLastAccessedTime();//客户端上一次发送与此会话关联的请求的时间，最后一次操作此会话时间
             long time = (end-start)/1000;  // 毫秒转换为秒
         %>
         <h1>您已经在此网页停留了<%=time %>秒</h1>
     </body>
 </html>

2.request

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             Cookie c1 = new Cookie("hw","hello world");
             Cookie c2 = new Cookie("hi","nice to meet you");
             c1.setMaxAge(300);//设置最大生存时间300秒
             c2.setMaxAge(30); //设置最大生存时间30秒
             response.addCookie(c1);
             response.addCookie(c2);
         %>
     </body>
 </html>

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             Cookie [] c = request.getCookies();
             if(c!=null){
                 for(int i=0;i<c.length;i++){
         %>
                 <h1>name:<%=c[i].getName() %>--value:<%=c[i].getValue() %></h1>
         <%
                 }
             }
         %>
     </body>
 </html>

3.定时刷新

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%!
             int count = 0;
         %>
         <%
             response.setHeader("refresh","1"); //每隔1秒刷新一次
         %>
         <h3>已经刷新了<%=count++ %>次</h3>
     </body>
 </html>

4.定时跳转页面一

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <h1>访问错误，5秒后跳转至首页，如果没有跳转，请点击<a href=hello.jsp>这里</a></h1>
         <%!
             int count = 0;
         %>
         <%
             response.setHeader("refresh","5; url=hello.jsp");
         %>
     </body>
 </html>

4.定时跳转页面二

 <!DOCTYPE html>
 <html>
 <head>
 <meta http-equiv="refresh" content="5;url=hello.jsp" charset="utf-8">
 <title>Insert title here</title>
 </head>
 <body>
     <h1>访问错误，5秒后跳转至首页，如果没有跳转，请点击<a href=hello.jsp>这里</a></h1>
 </body>
 </html>

5.重定向

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             response.sendRedirect("hello.jsp");
          %>
     </body>
 </html>

6.addcookie

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             Cookie c1 = new Cookie("hw","hello world");
             Cookie c2 = new Cookie("hi","nice to meet you");
             c1.setMaxAge(300);//设置最大生存时间300秒
             c2.setMaxAge(30); //设置最大生存时间30秒
             response.addCookie(c1);
             response.addCookie(c2);
         %>
     </body>
 </html>

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             Cookie [] c = request.getCookies();
             if(c!=null){
                 for(int i=0;i<c.length;i++){
         %>
                 <h1>name:<%=c[i].getName() %>--value:<%=c[i].getValue() %></h1>
         <%
                 }
             }
         %>
     </body>
 </html>

7.练习

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <form action="login.jsp" method="post">
             用户名:<input type="text" name="uname" ><br/>
             密    码:<input type="password" name="upass" ><br/>
             <input type="submit" value="登陆">
             <input type="reset" value="清空">
         </form>
         <%
             //用户名scott，密码orcl
             String name=request.getParameter("uname");
             String password=request.getParameter("upass");

         if(!(name==null||"".equals(name.trim())||password==null||"".equals(password.trim()))){
             if("scott".equals(name)&&"orcl".equals(password)){
                 response.setHeader("refresh","2;url=welcome.jsp");//2秒后跳转welcome页面
                 session.setAttribute("userName",name); //传值
         %>
                 <h1>登陆成功，两秒后跳转至欢迎页 </h1>
                 <h1>如果没有跳转，请点击<a href="welcome.jsp">这里</a></h1>
         <%
             }else{
         %>
                 <h3>用户名或密码错误，请重新登陆...</h3>
         <%
                 response.setHeader("refresh","2;url=login.jsp");
             }
         }else{
         }
         %>
     </body>
 </html>

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
             session.invalidate();
             response.setHeader("refresh","2;login.jsp");
         %>
         <h2>注销成功，两秒后跳转至首页</h2>
         <h1>如果没有跳转，请点击<a href="login.jsp">这里</a></h1>
     </body>
 </html>

 <%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
 <!DOCTYPE html>
 <html>
     <head>
         <title>Insert title here</title>
     </head>
     <body>
         <%
         if(session.getAttribute("userName")!=null){
         %>
             <h2>欢迎<%=session.getAttribute("userName") %>登陆本系统</h2>
             <h1>注销请点击<a href="loginout.jsp">注销</a></h1>
         <%
         }else{
         %>
             <h1>请先<a href="login.jsp">登录</a></h1>
         <%
         }
         %>
     </body>
 </html>