ShoppingServlet代码如下：
	package servlet.user;
	import java.io.IOException;
	import java.util.ArrayList;
	import javax.servlet.RequestDispatcher;
	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 util.Validate;
	import bean.Cart;
	import bean.CartItem;
	public class ShoppingServlet extends HttpServlet {
		public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
			Validate validate = new Validate();
			String pathStr = "";
			String method = validate.getUnicode(request.getParameter("method"));
			String bookId = validate.getUnicode(request.getParameter("bookId"));
			String bookName = validate.getUnicode(request.getParameter("bookName"));
			String bookQuantityStr = request.getParameter("bookQuantity");
			String bookPriceStr = request.getParameter("bookPrice");
			int bookQuantity =0;
			double bookPrice = 0.0d;
			if(bookQuantityStr!=null)
				bookQuantity = Integer.parseInt(bookQuantityStr);
			if(bookPriceStr!=null)
				bookPrice= Double.parseDouble(bookPriceStr);
			HttpSession session = request.getSession();
			ArrayList login = (ArrayList) session.getAttribute("login");
			if(login == null || login.equals("")){
				pathStr="/user/error.jsp";
			} else {
				pathStr = "/user/cart.jsp";
				CartItem cartItem = new CartItem();
				cartItem.setId(bookId);
				cartItem.setName(bookName);
				cartItem.setQuantity(bookQuantity);
				cartItem.setPrice(bookPrice);
				Cart cart = (Cart)session.getAttribute("cart");
				if(cart==null)
					cart = new Cart();
				//添加书籍到购物车
				if("add".equals(method)){
					cart.addCartItem(cartItem);
				}
				//根据id删除书籍
				else if("delete".equals(method)){
					cart.removeCartItem(bookId);
				}
				//修改指定书籍的数量
				else if("update".equals(method)){
					int updateBookQuantity = Integer.parseInt(request.
							getParameter("updateBookQuantity"+bookId));
					cart.updateCartItem(bookId, updateBookQuantity);
				}
				//清空购物车
				else if("removeAll".equals(method)){
					cart.clearCart();
				}
				session.setAttribute("cart", cart);
			}
			RequestDispatcher rd = request.getRequestDispatcher(pathStr);
			rd.forward(request, response);
		}
		public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
			doGet(request, response);
		}
	}