Session (shopping cart) object and Application object

First, the Session1.jsp page, the detailed code is as follows:

<%@ page language="java" import="java.util.*" pageEncoding="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 'Session1.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>
  
    <form action="Session2.jsp" method="post">
    请输入书名：<input type="text" name="book">
    <input type="submit" value="添加购物车">
    </form><hr>
    
    购物车内容：<br>
    <%
    //从购物车中取出books
     //getAttribute（）返回的是Object类型，用户将内容从sessin中取出的时候必须进行强制转换
    ArrayList books=(ArrayList)session.getAttribute("books");
    if(books!=null){
      for(int i=0;i<books.size();i++){
          String book=(String)books.get(i);
          out.print(book+"<br>");
      }
    }
     %>
  </body>
</html>

Then create the Session2.jsp page, the detailed code is as follows:

<%@ page language="java" import="java.util.*" pageEncoding="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 'Session2.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>
    <%
    //将内容放到购物车
    //从Session获取books，判断books是否为空
    ArrayList books=(ArrayList)session.getAttribute("books");
    if(books==null){
      books=new ArrayList();//实例化一个集合
      session.setAttribute("books", books);//想session中存放一个集合对象
    }
    //获取书名
    request.setCharacterEncoding("UTF-8");
    String book=request.getParameter("book");
    if(book!=null){
       books.add(book);//把获取到的书名book添加到books集合中
    }
    response.sendRedirect("Session1.jsp");
     %>
  </body>
</html>

Run the Session1.jsp page, the result:

Added content:

Application realizes the number of visits:

Create the Application.jsp page, the detailed code is as follows:

<%@ page language="java" import="java.util.*" pageEncoding="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 'Application.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>
    <%
      //第一次访问，实例化count，需要强制转换为封装类
      Integer count=(Integer)application.getAttribute("count");
      if(count==null){
         count=new Integer(0);
      }
      count++;
      application.setAttribute("count",count);
     %>
     您是该页面的第<%=count %>个访问者
  </body>
</html>

After the service area is started, the Application object is automatically created, and this object will be saved until the server is shut down

Run the page:

Close the page to revisit:

closed, open

Session (shopping cart) object and Application object

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