(1)用servlet实现简单的购物车系统，项目结构例如以下：（新建web Project项目  仅仅须要AddItemServlet ， ListItemServlet。exam403.jsp三个文件就可以。其它的不用管）

jsp javabean jsp javabean servlet 购物车_java

（2）exam403.jsp代码例如以下：

<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head>

<body>
<form id="form1" name="form1" method="post" action="/servletProject/addItem">
  <label></label>
  商品:
  <select name="itemID" id="itemID">
    <option value="洗衣粉">洗衣粉</option>
    <option value="香皂">香皂</option>
    <option value="食用油">食用油</option>
  </select>
  <p>数量:
    <label>
    <input name="quantity" type="text" id="quantity" value="1" />
    </label>
    <label>
    <input type="submit" name="Submit" value="提交" />
    </label>
    <a href="/servletProject/listItem">查看购物车</a></p>
</form>
</body>
</html>


（3）AddItemServlet代码例如以下：

package com.lc.shoppingCar;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
public class AddItemServlet extends HttpServlet 
{  
  protected void doGet(HttpServletRequest request,HttpServletResponse response)
                         throws ServletException,java.io.IOException
   {
      ServletContext application=getServletContext() ;
      ServletConfig config=getServletConfig() ;
      response.setContentType("text/html;charset=gb2312");
      PrintWriter out=response.getWriter(); 
      HttpSession session =request.getSession();
      request.setCharacterEncoding("gb2312");
      
      //读取表单传入的商品ID及数量
     String id=request.getParameter("itemID"); 
	 String num=request.getParameter("quantity");
	 if(id!=null && num.length()!=0)
	 {  //从Sessionn中读取购物车
		HashMap shoppingCar=(HashMap)session.getAttribute("shoppingCar");
	    if(shoppingCar==null)
        shoppingCar=new HashMap();
	    //将商品加入到购物车中
	    String onum=(String)shoppingCar.get(id);
	    if(onum==null)
	        shoppingCar.put(id,num);
	    else
	    {
	       int n1=Integer.parseInt(num);
		   int n2=Integer.parseInt(onum);
		   String result=String.valueOf(n1+n2);
		   shoppingCar.put(id,result);
	     }   
         //将购物车写回session中保存
	     session.setAttribute("shoppingCar",shoppingCar); 
	   }
	   else  //假设传入的商品ID号为空或数量为空。显示提示信息
	     System.out.print("商品ID号为空会或数量为空！");
	  //返回商品列表页
	  response.sendRedirect("/servletProject/exam403.jsp");   
      }	
      
protected void doPost(HttpServletRequest request,HttpServletResponse response)
                                throws ServletException,java.io.IOException
  {
  	   doGet(request,response);
  	}
}


（4）ListItemServlet代码例如以下：

package com.lc.shoppingCar;


import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
public class ListItemServlet extends HttpServlet 
{  
  protected void doGet(HttpServletRequest request,HttpServletResponse response)
                         throws ServletException,java.io.IOException
   {
      ServletContext application=getServletContext() ;
      ServletConfig config=getServletConfig() ;
      response.setContentType("text/html;charset=gb2312");
      PrintWriter out=response.getWriter(); 
      HttpSession session =request.getSession();
      request.setCharacterEncoding("gb2312");
      
       //从session中获取购物车
		HashMap shoppingCar=(HashMap)session.getAttribute("shoppingCar");
	  //显示购物车中的内容
	   if(shoppingCar!=null)
	   {
	      Set show=shoppingCar.entrySet();
	      Iterator it=show.iterator();
	      while(it.hasNext())
	      {
	        out.print(it.next()+"<br>");
	       }
	   }
	   else
	   	  out.print("购物车为空。"); 
      }	
      
protected void doPost(HttpServletRequest request,HttpServletResponse response)
                                throws ServletException,java.io.IOException
  {
  	   doGet(request,response);
  	}
}


（5）实现效果例如以下：

訪问：http://localhost:8080/servletProject/exam403.jsp    学则商品 提交 

jsp javabean jsp javabean servlet 购物车_html_02

点击查看购物车：

jsp javabean jsp javabean servlet 购物车_xml_03

OK！

简单的购物车 到此结束！