book.jsp是商品列表页面，我们这里是图书。cart.jsp是购物小车页面。
最简单的购物车商品数量只能是1，只能添加，不能删除。
//book.jsp，图书列表
<?xml version="1.0" encoding="UTF-8" ?>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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=UTF-8" />
<title>Insert title here</title>
</head>
<body>
<%
String[] books={"JSP","Java","Economics","Capital",
"MIS","ERP","CRM","DataMing"};
%>
<table width="80%" border="1">
<tr>
<td>Books</td>
<td>Operations</td>
</tr>
<%
for(int i=0;i<books.length;i++){
%>
<tr>
<td><%=books[i] %></td>
<td><a href="cart.jsp?book=<%=books[i]%>">add to cart</a></td>
</tr>
<%
}
%>
</table>
<a href="cart.jsp">show cart</a>
</body>
</html>
//cart.jsp，购物小车
<?xml version="1.0" encoding="UTF-8" ?>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="java.util.*"%>
<!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=UTF-8" />
<title>Insert title here</title>
</head>
<body>
<%
String bookName = request.getParameter("book");
ArrayList cart = (ArrayList)session.getAttribute("cart");
if(cart==null){
//first time /
cart = new ArrayList();
session.setAttribute("cart",cart);
}
boolean found = false;
if(bookName!=null&&!bookName.trim().equals("")){
for(int i=0;i<cart.size();i++){
String current = (String)cart.get(i);
if(bookName.equals(current)){
found=true;
break;
}
}
if(!found){
cart.add(bookName);
}
}
%>
<h1>Cart</h1>
<table width="700" border="1">
<tr>
<td>Books</td>
<td>Count</td>
</tr>
<%
for(int i=0;i<cart.size();i++){
String current = (String)cart.get(i);
out.println("<tr><td>"+current+"</td><td>1</td></tr>");
}
%>
</table>
<a href="book.jsp">continue</a>
</body>
</html>