一、结合之前所学的相关技术，编写代码实现以下购物车功能

1. 编写一个页面，展现商品列表（静态页面），页面右上方有登陆、结账和查看购物车三个按钮，下方展示网站历史访问的人数

2. 用户点击商品后，可以将商品加入购物车

3. 用户点击登陆，跳转到登陆页面

4. 用户点击结账，若已登陆跳转至结账页面，否则跳转到登陆页面登陆后再跳转到结账页。

5. 用户点击查看购物车按钮，跳转至购物车页面，可查看购物车列表、增加商品数量或者删除商品

要实现一个完整的购物车功能，其实涉及到的技术点还挺多的，从前端页面展示到后端数据库交互，再到Session管理，每一步都得衔接上。下面就把整个实现过程拆解开来，一步步看。

1. 实现的功能运行截图如下

（1）商品列表页面home.jsp

（2）登录账号页面/未登录点击结账页面

（3）重新登录页面（记住上次登录的用户名和密码）

（4）点击任意商品加入购物车之后查看购物车

（5）增加或减少商品

（6）商品数量减为0时移除

（7）点击去结算，展示总金额

2. 数据库test存放的表格

（1）user表

（2）product表

导入jar包

3. 实体类

（1）User

package com.ryx.web.sy7;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@NoArgsConstructor
@AllArgsConstructor
@Data
@Builder
public class User {
    private String username;
    private String password;
}

（2）Product.ja va

package com.ryx.web.sy7;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import ja va.math.BigDecimal;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class Product {
    Integer id;
    String name;
    String imagePath;
    BigDecimal price;
    String description;
}

（3）ProductVo

package com.ryx.web.sy7;

import lombok.Getter;
import lombok.Setter;

import ja va.math.BigDecimal;

public class ProductVo extends Product {
    @Getter
    @Setter
    Integer count; //统计数量

    public ProductVo(Integer id, Integer count, String name, double price, String imagePath) {
        super();
        this.id = id;
        this.count = count;
        this.name = name;
        this.price = BigDecimal.valueOf(price);
        this.imagePath=imagePath;
    }
}

4. CartController.ja va

package com.ryx.web.sy7;

import lombok.SneakyThrows;
import org.springframework.util.ObjectUtils;

import ja vax.servlet.ServletException;
import ja vax.servlet.annotation.WebServlet;
import ja vax.servlet.http.HttpServlet;
import ja vax.servlet.http.HttpServletRequest;
import ja vax.servlet.http.HttpServletResponse;
import ja vax.servlet.http.HttpSession;
import ja va.io.IOException;
import ja va.sql.*;
import ja va.util.HashMap;
import ja va.util.Map;

@WebServlet(name = "shoppingCart", value = "/shoppingCart")
public class CartController extends HttpServlet {

//    连接数据库
    private static final String DB_URL = "jdbc:mysql://localhost:3306/test";
    private static final String DB_USERNAME = "root";
    private static final String DB_PASSWORD = "abc1234";

    @SneakyThrows
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Integer id = Integer.valueOf(request.getParameter("id"));
        String op = request.getParameter("op");
        String whereCome = request.getHeader("Referer");
        String redirectPath = null;

//        如果在主页点击加入购物车超链接，不跳转
        if (whereCome.equals("http://localhost:8080/sy7/home.jsp")) {
            redirectPath = request.getContextPath() + "/sy7/home.jsp";
        } else {
//            如果在购物车页面增加或删除商品也不跳转
            redirectPath = request.getContextPath() + "/sy7/cart.jsp";
        }

        HttpSession session = request.getSession();
        Map cart = (Map) session.getAttribute("cart");
        if (ObjectUtils.isEmpty(cart)) {
            cart = new HashMap();
        }

        switch (op) {
//            添加商品
            case "add":
                if (!ObjectUtils.isEmpty(cart.get(id))) {
                    ProductVo productVo = cart.get(id);
                    productVo.setCount(productVo.getCount() + 1);
                    cart.put(id, productVo);
                } else {
                    Class.forName("com.mysql.jdbc.Driver");
                    try (Connection conn = DriverManager.getConnection(DB_URL, DB_USERNAME, DB_PASSWORD)) {
                        String query = "SELECT * FROM product WHERE id = ?";
                        try (PreparedStatement stmt = conn.prepareStatement(query)) {
                            stmt.setInt(1, id);
                            try (ResultSet rs = stmt.executeQuery()) {
                                if (rs.next()) {
                                    String name = rs.getString("name");
                                    double price = rs.getDouble("price");
                                    String imagePath = rs.getString("image_path");
                                    Integer iid = rs.getInt("id");
                                    ProductVo productVo = new ProductVo(iid, 1, name, price, imagePath);
                                    cart.put(id, productVo);
                                }
                            }
                        }
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }
                }
                break;

//          减少商品
            case "sub":
                if (!ObjectUtils.isEmpty(cart.get(id))) {
                    ProductVo productVo = cart.get(id);
//                    防止出现负数
                    if (productVo.getCount() > 1) {
                        productVo.setCount(productVo.getCount() - 1);
                        cart.put(id, productVo);
                    } else {
//                        如果小于1则移除商品
                        cart.remove(id);
                    }
                }
                break;
        }

        session.setAttribute("cart", cart);
        response.sendRedirect(redirectPath);
    }
}

5. JSP页面

（1）展现商品列表（home.jsp）

CSS

table {
    border-collapse: collapse;
    width: 86%;
}
table, th, td {
    border: 1px solid gainsboro;
}
td {
    width: 200px;
}
.redText {
    color: #FF0000;
}
.pinkTest {
    color: lightpink;
}

<%@ page import="ja va.sql.Connection" %>
<%@ page import="ja va.sql.PreparedStatement" %>
<%@ page import="ja va.sql.ResultSet" %>
<%@ page import="ja va.sql.DriverManager" %>
<%--
  Created by IntelliJ IDEA.
  User: 86189
  Date: 2023/10/23
  主页面展示商品
--%>
<%@ page language="ja va" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>



    
    
   


欢迎来到小煊的美妆铺~
登录
结算
查看购物车



    <%---------------------- 获取商品数据 -----------------------------%>
    <%
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
        try {
            //连接数据库
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "abc1234");
            String query = "SELECT * FROM product";
            stmt = conn.prepareStatement(query);
            rs = stmt.executeQuery();
            int count = 0;
            while (rs.next()) {
                int id = rs.getInt("id"); //商品编号
                String name = rs.getString("name"); //商品名
                double price = rs.getDouble("price"); //价格
                String description = rs.getString("description"); //描述
                String imagePath = rs.getString("image_path"); // 图片路径
                //五个商品即换行
                if (count % 5 == 0) {
                    out.println("");
                }
    %>
    
    <%
                //闭合标签
                if (count % 5 == 4) {
                    out.println("");
                }
                count++;
            }
            //最后不足五个，自动闭合
            if (count % 5 != 0) {
                out.println("");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                rs.close();
            } catch (Exception e) {
            }
            try {
                stmt.close();
            } catch (Exception e) {
            }
            try {
                conn.close();
            } catch (Exception e) {
            }
        }
    %>


        <%--------------------------图片-----------------------%>
        

        <%--------------------------商品描述-----------------------%>
        
 <%=name%><%=description%> 
        <%--------------------------价格-----------------------%>
        
 ￥：<%=price%> 
        <%--------------------------加购-----------------------%>
        

            

                "/>加入购物车
                
            
        

    


<%
//    初始化历史访问人数
    Integer accessCount = (Integer) session.getAttribute("accessCount");
    if (accessCount == null) {
        accessCount = new Integer(0);
    } else {
        accessCount = new Integer(accessCount.intValue() + 1);
    }
    session.setAttribute("accessCount", accessCount);
%>
历史访问人数：<%= accessCount %> 

（2）登陆页面(login.jsp)

JSP程序段＋JS代码

<%-----------------------JSP程序段---------------------------%>
<%
    request.setCharacterEncoding("UTF-8");
    //一次性登录
    String msg = request.getParameter("msg");
%>
<%
    if (msg != null) {
        String errorMessage = "账号或密码有误，请重新输入！";
%>

<%
    }
%>
<%-- 读取Cookie --%>
<%
    Cookie[] cookies = request.getCookies();
    String sa vedUsername = null;
    String sa vedPassword = null;
    if (cookies != null) {
        for (Cookie cookie : cookies) {
            if (cookie.getName().equals("username")) {
                sa vedUsername = cookie.getValue();
            } else if (cookie.getName().equals("password")) {
                sa vedPassword = cookie.getValue();
            }
        }
    }
%>

HTML

<%--
  Created by IntelliJ IDEA.
  User: 86189
  Date: 2023/10/13
  登录页面
--%>
<%@ page contentType="text/html;charset=UTF-8" language="ja va" pageEncoding="UTF-8" %>


    
    


<%-----------------------登录表单--------------------------%>

    
登录账号
    

    

        

            

                用户名：
            
            
" id="username" name="username" required>
        
        

            
密码：
            
" id="password" name="password" required>
            

        
        

            

          
            
记住密码
        
    

（3）登录后台处理页面（loginAction.jsp）

<%@ page import="com.ryx.web.sy7.User" %>
<%@ page import="ja va.sql.*" %>
<%--
  Created by IntelliJ IDEA.
  User: 86189
  Date: 2023/10/13
  判断输入的用户信息是否存在数据库
--%>
<%@ page contentType="text/html;charset=UTF-8" language="ja va" %>
<%!
    public boolean validateUser(String username, String password) {
        // 使用JDBC连接数据库
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        String driver = "com.mysql.cj.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/test";  //数据库
        String user = "root"; //账户
        String psword = "abc1234"; //密码
        try {
            try {
                try {
                    Class.forName(driver);
                } catch (ClassNotFoundException e) {
                    throw new RuntimeException(e);
                }
                // 获取数据库连接
                connection = DriverManager.getConnection(url, user, psword);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            try {
                // 构造查询语句
                String query = "SELECT * FROM test.user WHERE username =  ? ";
                // 创建PreparedStatement对象，并设置参数
                statement = connection.prepareStatement(query);
                statement.setString(1, username);
                // 执行查询
                resultSet = statement.executeQuery();
                // 验证用户名和密码
                if (resultSet.next()) {
                    String storedPassword = resultSet.getString("password");
                    if (storedPassword.equals(password)) {
                        return true;
                    }
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        } finally {
            // 关闭连接和释放资源
            try {
                if (resultSet != null) {
                    resultSet.close();
                }
                if (statement != null) {
                    statement.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return false;
    }
 %>
<%
    request.setCharacterEncoding("UTF-8");
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    boolean isValidUser = validateUser(username, password);
    //验证成功
    if (isValidUser) {
        // 创建形 Builder 构造者模式，链式编程
        User user = User.builder()
                    .username(username)
                    .password(password)
                    .build();
        String remember = request.getParameter("remember");
        if (remember != null && remember.equals("member")) {
            // 创建存储用户名和密码的Cookie对象
            Cookie usernameCookie = new Cookie("username", username);
            Cookie passwordCookie = new Cookie("password", password);
            // 设置Cookie的有效期（设置为7天）
            usernameCookie.setMaxAge(7 * 24 * 60 * 60); // 7天
            passwordCookie.setMaxAge(7 * 24 * 60 * 60); // 7天
            // 将Cookie添加到响应中
            response.addCookie(usernameCookie);
            response.addCookie(passwordCookie);
        } else {
            // 删除之前保存的Cookie
            Cookie[] cookies = request.getCookies();
            if (cookies != null) {
                for (Cookie cookie : cookies) {
                    if (cookie.getName().equals("username") || cookie.getName().equals("password")) {
                        cookie.setMaxAge(0); // 设置有效期为0，即立即删除
                        response.addCookie(cookie);
                    }
                }
            }
        }
        session.setAttribute("user", user);
        //跳转到其他页面
        response.sendRedirect("home.jsp");
    } else {
        //验证失败，提示出错
        response.sendRedirect("login.jsp?msg=failed");
    }
 %>

（4）结账页面（checkout.jsp）

HTML+JSP+JSTL

<%@ taglib prefix="c" uri="http://ja va.sun.com/jsp/jstl/core" %>
<%@ page import="com.ryx.web.sy7.User" %>
<%@ page import="ja va.util.Map" %>
<%--
  Created by IntelliJ IDEA.
  User: 86189
  Date: 2023/10/21
  结算页面
--%>
<%@ page contentType="text/html;charset=UTF-8" language="ja va" pageEncoding="UTF-8" %>


<%--------------------判断用户是否登录-----------------------%>
<%
    //存储变量
    User user = (User) session.getAttribute("user");
    //    未登录用户跳转到登录页面
    if (user == null) {
        response.sendRedirect("login.jsp");
    }
%>

    
    


<%----------------- 获取购物车中的商品 ------------------------%>
订单信息
<%
    session = request.getSession();
    Map cart = (Map) session.getAttribute("cart");
    if (cart == null) {
        out.println("购物车为空");
        return;
    }
%>
<%--计算总价钱--%>


    
    <%--单个商品的总额--%>
    
    <%--所有商品的总额--%>
    


    
您应支付:￥${totalAmount}
    

        
    

（5）购物车页面（cart.jsp）

CSS

table {
    border-collapse: collapse;
}
table, th, td {
    border: 1px solid gainsboro;
}
.titleTest {
    color: lightpink;
}
td {
    width: 20%;
}
a {
   text-decoration: none;
}

HTML

<%@ page language="ja va" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<%@ taglib prefix="c" uri="http://ja va.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fn" uri="http://ja va.sun.com/jsp/jstl/functions" %>
<%--
  Created by IntelliJ IDEA.
  User: 86189
  Date: 2023/10/21
  购物车页面
--%>



    
    


我的购物车

    
            
                <%----------------------商品信息--------------------%>
                
                <%----------------------单价--------------------%>
                
                <%----------------------数量-/+--------------------%>
                
                <%----------------------金额--------------------%>
                

        

            
商品信息
            
单价
            
数量
            
金额
        
        

                
${product.name}
￥：${product.price}

                    ${product.id}
               "/>-
                    
                        ${product.count}
                    ${product.id}
               "/>+
                    
                
￥：${product.count*product.price}
            
        
    






    继续购物
    去结算