8.javaweb之session

session是客户端和服务端的一次会话

web的session是指用户在浏览某个网站时，从进入网站到关闭浏览器的这段时间，uyejiushi用户浏览这个网站所花费的时间。

session是一个时间的概念

在服务器的内存中保存着不同用户的session

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 'exersice.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最大生存期限
     session.setMaxInactiveInterval(10);//10秒钟，是秒过后再跳转则session不再保存
     %>
    Session创建时间：<%=sdf.format(d) %><br>
    Session的ID编号：<%=session.getId() %><br>
       从Session中换取用户名：<%=session.getAttribute("username") %><br>
    <a href = "session_page2.jsp" target = "_blank_">跳转</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 'exersice.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>page2</h1>
     Session的ID编号：<%=session.getId() %><br>
          从Session中换取用户名：<%=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]+"&nbsp;&nbsp");
     };
      %> <br>
  </body>
</html>