$13.95</option>
</select>
<b>Quantity: </b><input type="text" name="qty" SIZE="3" value=1>
<input type="hidden" name="action" value="ADD">
<input type="submit" name="Submit" value="Add to Cart">
</form>
</center>
<p>
<jsp:include page="Cart.jsp" flush="true" />
</body>
</html>
Listing 2:
Cart.jsp
<%@ page session="true" import="java.util.*, shopping.CD" %>
<%
Vector buylist = (Vector) session.getValue("shopping.shoppingcart");
if (buylist != null && (buylist.size() > 0)) {
%>
<center>
<table border="0" cellpadding="0" width="100%" bgcolor="#FFFFFF">
<tr>
<td><b>ALBUM</b></td>
<td><b>ARTIST</b></td>
<td><b>COUNTRY</b></td>
<td><b>PRICE</b></td>
<td><b>QUANTITY</b></td>
<td></td>
</tr>
<%
for (int index=0; index < buylist.size();index++) {
CD anOrder = (CD) buylist.elementAt(index);
%>
<tr>
<td><b><%= anOrder.getAlbum() %></b></td>
<td><b><%= anOrder.getArtist() %></b></td>
<td><b><%= anOrder.getCountry() %></b></td>
<td><b><%= anOrder.getPrice() %></b></td>
<td><b><%= anOrder.getQuantity() %></b></td>
<td>
<form name="deleteForm"
action="/examples/servlet/ShoppingServlet"
method="POST">
<input type="submit" value="Delete">
<input type="hidden" name= "delindex" value='<%= index %>'>
<input type="hidden" name="action" value="DELETE">
</form>
</td>
</tr>
<% } %>
<p>
<form name="checkoutForm"
action="/examples/servlet/ShoppingServlet"
method="POST">
<input type="hidden" name="action" value="CHECKOUT">
<input type="submit" name="Checkout" value="Checkout">
</form>
</center>
<% } %>
这里，Cart.jsp按照MVC的模式1处理基于SESSION的购物车的表现。请看Cart.jsp开始处的代码：
<%
Vector buylist = (Vector) session.getValue("shopping.shoppingcart");
if (buylist != null && (buylist.size() > 0)) {
%>
本质上，这段代码从SESSION中取出“购物车”。如果“购物车”为空或者没有被创建，它就什么也不显示。所以，在用户第一次访问应用时，其界面如图：
如果“购物车”不为空，用户选择的商品从车中取出，依次显示在页面上：
<%
for (int index=0; index < buylist.size(); index++) {
CD anOrder = (CD) buylist.elementAt(index);
%>
一旦生成一个物品的说明，就使用JSP按照事先设定的模板将其插入静态HTML页面。下图显示了用户选购一些物品后的界面：
需要注意的一个重要的地方是所有关于Eshop.jsp,Cart.jsp的处理有一个控制SERVLET，ShoppingServlet.java，代码在源程序3中：
Listing 3:
ShoppingServlet.java
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import shopping.CD;
public class ShoppingServlet extends HttpServlet {
public void init(ServletConfig conf) throws ServletException {
super.init(conf);
}
public void doPost (HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
HttpSession session = req.getSession(false);
if (session == null) {
res.sendRedirect("http://localhost:8080/error.html");
}
Vector buylist=
(Vector)session.getValue("shopping.shoppingcart");
String action = req.getParameter("action");
if (!action.equals("CHECKOUT")) {
if (action.equals("DELETE")) {
String del = req.getParameter("delindex");
int d = (new Integer(del)).intValue();
buylist.removeElementAt(d);
} else if (action.equals("ADD")) {
//any previous buys of same cd?
boolean match=false;
CD aCD = getCD(req);
if (buylist==null) {
//add first cd to the cart
buylist = new Vector(); //first order
buylist.addElement(aCD);
} else { // not first buy
for (int i=0; i< buylist.size(); i++) {
CD cd = (CD) buylist.elementAt(i);
if (cd.getAlbum().equals(aCD.getAlbum())) {
cd.setQuantity(cd.getQuantity()+aCD.getQuantity());
buylist.setElementAt(cd,i);
match = true;
} //end of if name matches
} // end of for
if (!match)
buylist.addElement(aCD);
}
}
session.putValue("shopping.shoppingcart", buylist);
String url="/jsp/shopping/EShop.jsp";
ServletContext sc = getServletContext();
RequestDispatcher rd = sc.getRequestDispatcher(url);
rd.forward(req, res);
} else if (action.equals("CHECKOUT")) {
float total =0;
for (int i=0; i< buylist.size();i++) {
CD anOrder = (CD) buylist.elementAt(i);
float price= anOrder.getPrice();
int qty = anOrder.getQuantity();
total += (price * qty);
}
total += 0.005;
String amount = new Float(total).toString();
int n = amount.indexOf('.');
amount = amount.substring(0,n+3);
req.setAttribute("amount",amount);
String url="/jsp/shopping/Checkout.jsp";
ServletContext sc = getServletContext();
RequestDispatcher rd = sc.getRequestDispatcher(url);
rd.forward(req,res);
}
}
private CD getCD(HttpServletRequest req) {
//imagine if all this was in a scriptlet...ugly, eh?
String myCd = req.getParameter("CD");
String qty = req.getParameter("qty");
StringTokenizer t = new StringTokenizer(myCd,"(北联网教程,专业提供视频软件下载)
……