创建商品类、servlet、el表达式

1.创建商品类，包括字段：id，name，type，brand，完善构造函数及get和set方法
2.创建一个servlet，在其中构造一个商品的ArrayList，并创建至少4个商品。将商品列表放入request中，将商品个数放到cookie中，并转发到list.jsp
3.在list.jsp中用el表达式和jstl商品的所有信息显示在表格中，将cookie中数据取出并显示

部分基于chartgpt编写

商品类的代码实现如下，包含 id，name，type，brand 四个字段和相应的构造函数和 get/set 方法：

public class Product {
    private int id;
    private String name;
    private String type;
    private String brand;
    
    public Product(int id, String name, String type, String brand) {
        this.id = id;
        this.name = name;
        this.type = type;
        this.brand = brand;
    }
    
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public String getType() {
        return type;
    }
    
    public void setType(String type) {
        this.type = type;
    }
    
    public String getBrand() {
        return brand;
    }
    
    public void setBrand(String brand) {
        this.brand = brand;
    }
}

在 Servlet 中，代码实现如下，在 init 方法中创建至少4个商品对象，并存储在 ArrayList 中，最后将 ArrayList 存放在 request 中，"productList" 键中，将商品数量存放在 cookie 中。

import java.util.ArrayList;
import javax.servlet.http.*;

public class ProductServlet extends HttpServlet {
    ArrayList<Product> productList = new ArrayList<>();
    
    public void init() {
        Product p1 = new Product(1, "iPhone X", "Mobile Phone", "Apple");
        Product p2 = new Product(2, "iPad Pro", "Tablet", "Apple");
        Product p3 = new Product(3, "Surface Pro", "Tablet", "Microsoft");
        Product p4 = new Product(4, "ThinkPad X1 Carbon", "Laptop", "Lenovo");
        productList.add(p1);
        productList.add(p2);
        productList.add(p3);
        productList.add(p4);
    }
    
    public void doGet(HttpServletRequest request,
            HttpServletResponse response) {
        Cookie cookie = new Cookie("productCount", Integer.toString(productList.size()));
        response.addCookie(cookie);
        
        request.setAttribute("productList", productList);
        request.getRequestDispatcher("list.jsp").forward(request, response);
    }
}

在 list.jsp 中通过 JSTL 指令实现了商品列表的显示，同时通过使用 EL 表达式获取 cookie 中的商品数量。

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Product List</title>
</head>
<body>
    <table border="1">
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>Type</th>
            <th>Brand</th>
        </tr>
        <c:forEach var="product" items="${productList}">
            <tr>
                <td>${product.id}</td>
                <td>${product.name}</td>
                <td>${product.type}</td>
                <td>${product.brand}</td>
            </tr>
        </c:forEach>
    </table>
    <p>Product Count: ${cookie.productCount.value}</p>
</body>
</html>

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创建商品类，包括字段：id，name，type，brand，完善构造函数及get和set方法。

public class Product {
    private int id;
    private String name;
    private String type;
    private String brand;

    public Product(int id, String name, String type, String brand) {
        this.id = id;
        this.name = name;
        this.type = type;
        this.brand = brand;
    }

    // Getters and setters
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }
}

创建一个servlet，在其中构造一个商品的ArrayList，并创建至少4个商品。将商品列表放入request中，将商品个数放到cookie中，并转发到list.jsp。


```java
import java.io.IOException;
import java.util.ArrayList;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ProductServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // 创建商品列表
        ArrayList<Product> productList = new ArrayList<Product>();
        productList.add(new Product(1, "iPhone 12", "智能手机", "苹果"));
        productList.add(new Product(2, "Galaxy S21", "智能手机", "三星"));
        productList.add(new Product(3, "iPad Pro", "平板电脑", "苹果"));
        productList.add(new Product(4, "Galaxy Tab S7", "平板电脑", "三星"));

        // 将商品列表添加到request中
        request.setAttribute("productList", productList);

        // 将商品个数放到cookie中
        Cookie productCountCookie = new Cookie("productCount", String.valueOf(productList.size()));
        response.addCookie(productCountCookie);

        // 转发到list.jsp
        request.getRequestDispatcher("list.jsp").forward(request, response);
    }
}


3. 在list.jsp中用el表达式和jstl商品的所有信息显示在表格中，将cookie中数据取出并显示。

```java
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>商品列表</title>
</head>
<body>
    <h1>商品列表</h1>
    <p>共有<c:out value="${cookie.productCount.value}" />件商品</p>
    <table border="1">
        <tr>
            <th>ID</th>
            <th>名称</th>
            <th>类型</th>
            <th>品牌</th>
        </tr>
        <c:forEach items="${requestScope.productList}" var="product">
            <tr>
                <td><c:out value