学习开发购物车模块
发现一个问题，如果web.xml中配置映射路径中/servlet/***,在serlet中，跳转的时候，会在路径中自动添加/servlet，这个真是非常的恶心。下次设置映射的时候，不加/servlet.
首先给出购买页。这里用静态页面。
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP ‘shoMerchandise.jsp‘ starting page</title>
</head>
<body>
<table width=424 " height="583" border="0" align="center">
<tr>
<td width="190"><img alt="hpcomputer"
src="images/hppavilion.jpg"></td>
<td width="224"><img src="images/lenovo.jpg">
<td>
</tr>
<tr>
<td>笔记本电脑</td>
<td>移动硬盘
</tr>
<tr>
<td>价格：5999.99元</td>
<td>价格：688.88</td>
</tr>
<tr>
<td>
<a href="servlet/AddShoppingCart?id=0001&name=笔记本电脑&price=5999.00"><img src="images/buybutton.gif" width="71" height="21" border="0" /></a>
</td>
<td>
<a href="servlet/AddShoppingCart?id=0002&name=移动硬盘&price=688.88"><img src="images/buybutton.gif" width="71" height="21" border="0"/></a>
</tr>
</table>
</body>
</html>
点击购买，跳转到addShoppingCart.java，这是一个servlet，处理的事件为把点击购买的商品添加到购物车中：
过程是，首先从session中读取shoppingcart，如果为空，则一个购物车类（通过javabean：ShoppingCart类），然后在session中新建一个购物车的信息。
session.setAttribute("shoppingcart", cart);
否则的话，就从session中读取出shoppingcart的信息。保存在javabean：ShoppingCart new cart中。
然后接收request传递到服务器的信息，并验证信息的合法性。
//获得商品的基本信息
String id=request.getParameter("id");
String name=request.getParameter("name");
byte source [] = name.getBytes("iso8859-1");
name = new String (source,"UTF-8");
String quantity=request.getParameter("q");
String price = request.getParameter("price");
System.out.println(id+name+quantity+price);
//检验要加入的商品信息
if(StringTool.validateNull(id)||StringTool.validateNull("name")||StringTool.validateNull("price")||StringTool.validateNull("quantity")){
printError(request,response);
return;
}
id=StringTool.filterHtml(id);
name=StringTool.filterHtml(name);
之后，执行cart的添加商品javebean：CartItem的addItem方法，把商品添加到cart中去。
try{
if(StringTool.validateNull(quantity)){
//根据传入的商品数据创建商品，然后利用addCartItem方法添加进购物车
cart.addItem(new CartItem(id,name,1,Double.parseDouble(price)));
System.out.println(Double.parseDouble(price));
}else{
cart.addItem(new CartItem(id,name,Integer.parseInt(quantity),Double.parseDouble(price)));
}
}catch(NumberFormatException e){
printError(request,response);
return;
}
这里并没有更新session，我这样理解：cart是建立的一个指针，它们之间（cart、session）是浅复制，所以不必更新session。
跳转到展示购物车的页面。
response.sendRedirect("GetShoppingCart");
这里就是我说的自动添加/servlet那个问题之一，按理说，按照映射的话，应该是/servlet/×××，但是由于是在servlet中跳转的，所以会自动在跳转路径中添加/servlet。
可以自己试一下。
如果商品添加失败，在输出错误信息。
下面是完整代码：AddShoppingCart.java
package com.cjg.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import com.cjg.bean.CartItem;
import com.cjg.bean.ShoppingCart;
import com.cjg.tools.*;
public class AddShoppingCart extends HttpServlet {
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
doPost(request,response);
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
response.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
response.setContentType("text/html;charset:utf-8");
HttpSession session = request.getSession();//获取session
ShoppingCart cart=(ShoppingCart) session.getAttribute("shoppingcart");
//当购物车为空时
if(cart==null){
cart=new ShoppingCart();
session.setAttribute("shoppingcart", cart);
}
//获得商品的基本信息
String id=request.getParameter("id");
String name=request.getParameter("name");
byte source [] = name.getBytes("iso8859-1");
name = new String (source,"UTF-8");
String quantity=request.getParameter("q");
String price = request.getParameter("price");
System.out.println(id+name+quantity+price);
//检验要加入的商品信息
if(StringTool.validateNull(id)||StringTool.validateNull("name")||StringTool.validateNull("price")||StringTool.validateNull("quantity")){
printError(request,response);
return;
}
id=StringTool.filterHtml(id);
name=StringTool.filterHtml(name);
try{
if(StringTool.validateNull(quantity)){
//根据传入的商品数据创建商品，然后利用addCartItem方法添加进购物车
cart.addItem(new CartItem(id,name,1,Double.parseDouble(price)));
System.out.println(Double.parseDouble(price));
}else{
cart.addItem(new CartItem(id,name,Integer.parseInt(quantity),Double.parseDouble(price)));
}
}catch(NumberFormatException e){
printError(request,response);
return;
}
response.sendRedirect("GetShoppingCart");
//System.out.println("ssss");
}
//商品添加失败的输出信息
private void printError(HttpServletRequest request, HttpServletResponse response)throws ServletException,IOException {
response.setContentType("text/html;charset:utf-8");
PrintWriter out =response.getWriter();
out.println("<html>");
out.println("<head><title>购买商品失败</title></head>");
out.println("<body>");
out.println("<h1>缺少商品参数或者商品参数不正确，添加商品到购物车中不成功</h1><br><br>");
out.println("<a href=\"/onlineshoppingcart/showMerchandise.htm\">继续浏览商品，添加商品到购物车</a><br>");
out.println("</body>");
out.println("</html>");
out.flush();
out.close();
}
}
时间： 2024-10-07 09:46:27