请高手帮我看一下这段代码哪里错了!!!
<html>
<head>
<title>添加订单内容</title>
</head>
<body>
<%@ page contentType="text/html;charset=gb2312"%>
<%@ page import="java.util.Vector" %>
<%
String bookid=(request.getParameter("bookNo"));
Vector order=new Vector();
if(session.getValue("indent")!=null)
{
order=(Vector)session.getValue("indent");
}
if(!order.contains(bookid))
{
order.addElement(bookid);
session.putValue("indent",order);
}
response.sendRedirect("bookstore.jsp");
%>
</body>
</html>