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下面的是我网上找的购物车系统，但是有缺陷，当你提交物品之后，重新刷新物品，你会发现购物车里面会自动添加一件物品，各位网友请多多指教小弟
shop.jsp
<%@ page contentType="text/html; charset=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>在线购书页面</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<form method="post" action="shopCheck.jsp">
<br>
请选择要添加的或者删除的图书种类
<hr>
添加商品:
<select name="item">
<option>java teaching</option>
<option>java web developing</option>
<option>java web</option>
<option>ssh2 developing</option>
<option>java programming</option>
<option>c program</option>
</select>
<br>
<hr>
<input type="submit" name="submit" value="add">
<input type="submit" name="submit" value="remove">
</form>
</body>
</html>
shopCheck.jsp
<%@ page contentType="text/html; charset=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>已购书信息</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<%
request.setCharacterEncoding("gbk");
%>
<jsp:useBean id="cart" scope="session" class="shop.Shop"/><!-- 这里相当于创建一个SHOP对象 -->
<jsp:setProperty name="cart" property="*"/>
<%
cart.processRequest(request);
%>
<br>你已经选购的书有：
<ol>
<%
String[] items = cart.getItems();
for (int i = 0; i < items.length; i++) {
%><li><%=items[i]%> <%
}
%>
</ol>
<br>
<hr>
</body>
</html>
Shop.java
package shop;
import java.util.*;
import javax.servlet.http.*;
public class Shop {
private Vector v = new Vector();
private String submit = null;
private String item = null;
private void addItem(String name) {
v.addElement(name);
}
private void removeItem(String name) {
v.removeElement(name);
}
public void setItem(String name) {
item = name;
}
public void setSubmit(String s) {
submit = s;
}
public String[] getItems() {
String[] s = new String[v.size()];
v.copyInto(s);
return s;
}
public void processRequest(HttpServletRequest request) {
if (submit == null) {//默认添加物品
//addItem(item);
reset();
}
if (submit.equals("add")) {
addItem(item);
}
if (submit.equals("remove")) {
removeItem(item);
}
reset();
}
private void reset() {
setSubmit(null);
setItem(null);
}
public String getSubmit() {
return submit;
}
public String getItem() {
return item;
}
}
缺陷，提交之后再刷新页面，很神器的缺陷就出来了
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原文地址：http://www.cnblogs.com/listentothecloud20150215/p/4295232.html
