(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）
（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 method="post" action="/servletProject/addItem"> <label></label> 商品: <select> <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 type="text" value="1" /> </label> <label> <input type="submit" value="提交" /> </label> <a href="https://www.jb51.net/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：:8080/servletProject/exam403.jsp 学则商品 提交
点击查看购物车：
OK！
简单的购物车 到此结束！