jsp购物车怎么实现

public class Product {
    private int id;
    private String name;
    private double price;
    // 省略构造函数、getter和setter方法
}

import java.util.ArrayList;
import java.util.List;

public class Cart {
    private List<Product> items = new ArrayList<>();

    public void addItem(Product product) {
        items.add(product);
    }

    public void removeItem(int productId) {
        items.removeIf(item -> item.getId() == productId);
    }

    public List<Product> getItems() {
        return items;
    }

    public double getTotalPrice() {
        return items.stream().mapToDouble(Product::getPrice).sum();
    }
}

<%@ page import="com.example.Cart" %>
<%@ page import="com.example.Product" %>

<%
    Cart cart = (Cart) session.getAttribute("cart");
    if (cart == null) {
        cart = new Cart();
        session.setAttribute("cart", cart);
    }
%>

<form action="addToCart.jsp" method="post">
    <input type="hidden" name="productId" value="1">
    <input type="submit" value="Add to Cart">
</form>

<%@ page import="com.example.Cart" %>
<%@ page import="com.example.Product" %>

<%
    int productId = Integer.parseInt(request.getParameter("productId"));
    Product product = new Product(productId, "Sample Product", 19.99);
    Cart cart = (Cart) session.getAttribute("cart");
    cart.addItem(product);
    response.sendRedirect("viewCart.jsp");
%>

<%@ page import="com.example.Cart" %>
<%@ page import="com.example.Product" %>

<%
    Cart cart = (Cart) session.getAttribute("cart");
%>
<table>
    <tr>
        <th>Product Name</th>
        <th>Price</th>
    </tr>
    <% for (Product product : cart.getItems()) { %>
        <tr>
            <td><%= product.getName() %></td>
            <td><%= product.getPrice() %></td>
        </tr>
    <% } %>
</table>
<p>Total: <%= cart.getTotalPrice() %></p>