JavaWeb:HttpSession(一)

Session机制:

1)、session机制采用的是在服务器端保持 HTTP 状态信息的方案 。

2)、当程序需要为某个客户端的请求创建一个session时,服务器首先检查这个客户端的请求里是否包含了一个session标识(即sessionId),如果已经包含一个sessionId则说明以前已经为此客户创建过session,服务器就按照session id把这个session检索出来使用(如果检索不到,可能会新建一个,这种情况可能出现在服务端已经删除了该用户对应的session对象,但用户人为地在请求的URL后面附加上一个JSESSION的参数)。如果客户请求不包含sessionId,则为此客户创建一个session并且生成一个与此session相关联的sessionId,这个session id将在本次响应中返回给客户端保存。

3)、方法:

--获取Session 对象:

request.getSession(), request.getSession(boolean Create);

--属性相关的:

getAttribute()、setAttribute()、removeAttribute()

--使HttpSession 失效:

invalidate()

--设置其最大时效

setMaxInactiveInterval()

4)、url 重写:它允许不支持Cookie的浏览器也可以与WEB服务器保持连续的会话。将会话标识号以参数形式附加在超链接的URL地址后面的技术称为URL重写。

<%= response.encodeURL("login.jsp")%>

5)、应用:一个简易的购物车

先看一下效果:

代码:

step1.jsp:

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <h4>Step1:选择要购买的书籍</h4>
11     <form action="<%= request.getContextPath() %>/processStep1" method="post">
12         <table border="1" cellpadding="10" cellspacing="0">
13             <tr>
14                 <td>书名</td>
15                 <td>购买</td>
16             </tr>
17             <tr>
18                 <td>Java</td>
19                 <td><input type="checkbox" name="book" value="Java"/></td>
20             </tr>
21             <tr>
22                 <td>Mysql</td>
23                 <td><input type="checkbox" name="book" value="MySql"/></td>
24             </tr>
25             <tr>
26                 <td>Oracle</td>
27                 <td><input type="checkbox" name="book" value="Oracle"/></td>
28             </tr>
29             <tr>
30                 <td colspan="2"><input type="submit" value="Submit"/></td>
31             </tr>
32         </table>
33     </form>
34 </body>
35 </html>

ProcessStep1Servlet .java:

 1 package com.hnust.javaweb;
 2 
 3 import java.io.IOException;
 4 import javax.servlet.ServletException;
 5 import javax.servlet.http.HttpServlet;
 6 import javax.servlet.http.HttpServletRequest;
 7 import javax.servlet.http.HttpServletResponse;
 8 
 9 public class ProcessStep1Servlet extends HttpServlet {
10     private static final long serialVersionUID = 1L;
11 
12     protected void doPost(HttpServletRequest request, HttpServletResponse response) 
13             throws ServletException, IOException {
14         //获取book 参数信息
15         String[] book = request.getParameterValues("book");
16         //放入
17         request.getSession().setAttribute("books", book);
18         //重定向到step2.jsp 页面,要用绝对路径
19         response.sendRedirect(request.getContextPath() + "/shoppingcart/step2.jsp");
20     }
21 
22 }

step2.jsp:

 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10     <h4>Step2:请输入寄送地址和信用卡地址</h4>
11     <form action="<%= request.getContextPath() %>/processStep2" method="post">
12         <table border="1" cellpadding="10" cellspacing="0">
13             <tr>
14                 <td colspan="2">基本信息</td>
15             </tr>
16             <tr>
17                 <td>姓名</td>
18                 <td><input type="text" name="name"/></td>
19             </tr>
20             <tr>
21                 <td>寄送地址:</td>
22                 <td><input type="text" name="address"/></td>
23             </tr>
24             <tr>
25                 <td colspan="2">信用卡信息</td>
26             </tr>
27             <tr>
28                 <td>种类</td>
29                 <td>
30                     <input type="radio" name="cardtype" value="Visa"/>Visa
31                     <input type="radio" name="cardtype" value="Master"/>Master
32                 </td>
33             </tr>
34             <tr>
35                 <td>卡号</td>
36                 <td><input type="text" name="card"/></td>
37             </tr>
38             <tr>
39                 <td colspan="2"><input type="submit" value="Submit"/></td>
40             </tr>
41         </table>
42     </form>
43 </body>
44 </html>
ProcessStep2Servlet .java:
 1 package com.hnust.javaweb;
 2 
 3 import java.io.IOException;
 4 import javax.servlet.ServletException;
 5 import javax.servlet.http.HttpServlet;
 6 import javax.servlet.http.HttpServletRequest;
 7 import javax.servlet.http.HttpServletResponse;
 8 
 9 public class ProcessStep2Servlet extends HttpServlet {
10     private static final long serialVersionUID = 1L;
11 
12     protected void doPost(HttpServletRequest request, HttpServletResponse response) 
13             throws ServletException, IOException {
14         //获取请求参数
15         String name = request.getParameter("name");
16         String address = request.getParameter("address");
17         String cardtype = request.getParameter("cardtype");
18         String card = request.getParameter("card");
19         //封装
20         Customer customer = new Customer(name, address, cardtype, card);
21         //放入
22         request.getSession().setAttribute("customers", customer);
23         //重定向到step3.jsp 页面,使用绝对路径
24         response.sendRedirect(request.getContextPath() + "/shoppingcart/step3.jsp");
25     }
26 
27 }

注意要建一个 Customer 实体类,来封装 step2 里面的信息。代码就不贴了。

step3.jsp:

 1 <%@page import="com.hnust.javaweb.Customer"%>
 2 <%@ page language="java" contentType="text/html; charset=UTF-8"
 3     pageEncoding="UTF-8"%>
 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 5 <html>
 6 <head>
 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 8 <title>Insert title here</title>
 9 </head>
10 <body>
11     <h4>Step3:订单确认</h4>
12     <%
13         String[] books = (String[]) session.getAttribute("books");
14         Customer cus = (Customer) session.getAttribute("customers");
15     %>
16     <table border="1" cellpadding="10" cellspacing="0">
17         <tr>
18             <td>顾客姓名</td>
19             <td><input type="text" value="<%= cus.getName() %>"/></td>
20         </tr>
21         <tr>
22             <td>地址</td>
23             <td><input type="text" value="<%= cus.getAddress() %>"/></td>
24         </tr>
25         <tr>
26             <td colspan="2">付款信息</td>
27         </tr>
28         <tr>
29             <td>信用卡类型</td>
30             <td><input type="text" value="<%= cus.getCardtype() %>"/></td>
31         </tr>
32         <tr>
33             <td>卡号</td>
34             <td><input type="text" value="<%= cus.getCard()%>"/></td>
35         </tr>
36         <tr>
37             <td colspan="2">订货项目</td>
38         </tr>
39         <tr>
40             <td></td>
41             <td>
42                 <%
43                     for(String book : books){
44                         out.print(book);
45                         out.print("<br>");
46                     }
47                 %>
48             </td>
49         </tr>
50     </table>
51 </body>
52 </html>

over。

洗洗睡觉,明天继续^_^。

posted @ 2017-01-11 22:38  稻小白  阅读(34803)  评论(0编辑  收藏