eclipse的web项目实现Javaweb购物车的方法

package Beans;

import java.util.HashMap;

public class Cart {
 private HashMap cartItems=new HashMap();//购物车中添加的商品
 
 private double total;//总计
 
 public HashMap getCartItems() {
 return cartItems;
 }
 public void setCartItems(HashMap cartItems) {
 this.cartItems = cartItems;
 }
 
 public double getTotal() {
 return total;
 }
 
 public void setTotal(double total) {
 this.total = total;
 }

}

package Beans;

public class CartItem {
  private Product product;//商品
 
 private int buyNum;//个数
 
 private double subTotal;//小计
 
 public Product getProduct() {
 return product;
 }
 
 public void setProduct(Product product) {
 this.product = product;
 }
 
 public int getBuyNum() {
 return buyNum;
 }
 
 public void setBuyNum(int buyNum) {
 this.buyNum = buyNum;
 }
 
 public double getSubTotal() {
 return subTotal;
 }
 
 public void setSubTotal(double subTotal) {
 this.subTotal = subTotal;
 }

}

package Beans;

public class Product {
 private String pid;//商品编号
 private String name;//商品名
 private double price;//商品价格
 public String getPid() {
 return pid;
 }
 public void setPid(String pid) {
 this.pid = pid;
 }
 public String getName() {
 return name;
 }
 public void setName(String name) {
 this.name = name;
 }
 public double getPrice() {
 return price;
 }
 public void setPrice(double price) {
 this.price = price;
 }
 
 public Product(String pid,String name,double price) {
 // TODO Auto-generated constructor stub
 this.pid = pid;
 this.name = name;
 this.price = price;
 }
 
}

package Service;

import java.util.HashMap;

import Beans.CartItem;
import Beans.Product;

public class ProductService {
 
 private HashMap cartItems=new HashMap();
 
 public ProductService() //构造函数
 {
  CartItem cartltem1=new CartItem();
  CartItem cartltem2=new CartItem();
  Product product1=new Product("001","Mobilephone",1000);
  Product product2=new Product("002","Watch",100);
  cartltem1.setProduct(product1);
  cartltem2.setProduct(product2);
 cartItems.put("001",cartltem1);
 cartItems.put("002", cartltem2);
 }
 
 public Product findProductbypid(String pid)
 {
 CartItem cartItem=cartItems.get(pid);
 Product product=cartItem.getProduct();
 return product;
 }
}

package Servlet;


import java.io.IOException;
import java.util.HashMap;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import Beans.Cart;
import Beans.CartItem;
import Beans.Product;
import Service.ProductService;


@WebServlet("/productServlet")
public class ProductServlet extends HttpServlet{
 
 /**
 * 
 */
 private static final long serialVersiOnUID= 1L;


 
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 
 ProductService productService = new ProductService();
 
 
 String pid=(String)req.getParameter("Product");
 int buyNum=Integer.parseInt(req.getParameter("number"));
 HttpSession session=req.getSession();
 Cart cart=(Cart)session.getAttribute("cart");
 if(cart==null) {
 cart=new Cart();
 }
 CartItem cartItem=new CartItem();
 cartItem.setBuyNum(buyNum);
 
 Product product=productService.findProductbypid(pid);
 cartItem.setProduct(product);
 double subTotal=product.getPrice()*buyNum;
 cartItem.setSubTotal(subTotal);
 
 HashMap cartItems=cart.getCartItems();
 double newSubTotal=0;
 if(cartItems.containsKey(pid)) {
 CartItem item=cartItems.get(pid);
 
 int oldBuyNum= item.getBuyNum();
 oldBuyNum=oldBuyNum+buyNum;
 item.setBuyNum(oldBuyNum);
 
 double oldSubTotal= item.getSubTotal();
 newSubTotal=buyNum*product.getPrice();
 oldSubTotal=oldSubTotal+newSubTotal;
 item.setSubTotal(oldSubTotal);
 }
 else {
 cartItems.put(pid, cartItem); 
 newSubTotal=buyNum*product.getPrice();
 }
 double total=cart.getTotal()+newSubTotal;
 cart.setTotal(total);
 cart.setCartItems(cartItems);
 session.setAttribute("cart", cart);
 req.getRequestDispatcher("cart.jsp").forward(req, resp); 
 }
  
}

<%@page import="org.apache.jasper.tagplugins.jstl.core.ForEach"%>
<%@ page language="java" cOntentType="text/html; charset=ISO-8859-1"
 pageEncoding="ISO-8859-1"%>
 <%@
 page import="Beans.Cart"
 %>
 <%@
 page import="Beans.CartItem"
 %>
 <%@
 page import="Beans.Product"
 %>
 <%@page import="java.util.*"%>








<% Cart cart=(Cart)request.getSession().getAttribute("cart");
  if(cart==null) {
 %>
 
It is nothing!
 <%
  }
  else{
  HashMap cartItems=cart.getCartItems();
  double total=cart.getTotal(); 
  %>
  Your product list:

  <%
  Set keys=cartItems.keySet();
  Iterator iter = keys.iterator();
  while(iter.hasNext()){
  String key= iter.next();
  CartItem cartItem=cartItems.get(key);
  Product product=cartItem.getProduct();
  out.print(product.getName()+" ") ;
  out.println("price:"+product.getPrice()+"$") ;
  out.println("number:"+cartItem.getBuyNum());
  };
  %>
 

 <%
 out.print("    total:"+total+"$");
 }
 %>
  
 

<%@ page language="java" cOntentType="text/html; charset=ISO-8859-1"
 pageEncoding="ISO-8859-1"%>






 
 Please select the item you want to buy.

 /productServlet" method="post">
 Mobile phone(1000$)
 

 Watch(100$)
 

 please input the number!
 number: