Java简易点餐系统

Java点餐系统，包括菜单管理、用户身份验证、订单处理和支付功能，并将数据存储到MySQL数据库中。

### 准备工作

首先，确保你已经创建了MySQL数据库，并且拥有以下两个表格来存储菜单和用户信息：

#### Menu 表结构

```sql
CREATE TABLE Menu (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    price DECIMAL(10, 2) NOT NULL
);
```

#### Users 表结构

```sql
CREATE TABLE Users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    password VARCHAR(50) NOT NULL,
    isAdmin BOOLEAN NOT NULL
);
```

### Java 代码实现

#### MenuItem 类

```java
public class MenuItem {
    private int id;
    private String name;
    private double price;

    public MenuItem(int id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    // Getters and setters
}
```

#### Menu 类

```java
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class Menu {
    private Connection conn;

    public Menu() {
        try {
            this.conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/your_database_name", "username", "password");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public List<MenuItem> getMenuItems() {
        List<MenuItem> menuItems = new ArrayList<>();
        String sql = "SELECT * FROM Menu";

        try (Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery(sql)) {

            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                double price = rs.getDouble("price");
                menuItems.add(new MenuItem(id, name, price));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return menuItems;
    }

    public MenuItem getMenuItemByName(String name) {
        String sql = "SELECT * FROM Menu WHERE name = ?";

        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, name);
            ResultSet rs = stmt.executeQuery();

            if (rs.next()) {
                int id = rs.getInt("id");
                double price = rs.getDouble("price");
                return new MenuItem(id, name, price);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return null;
    }

    public void addMenuItem(MenuItem item) {
        String sql = "INSERT INTO Menu (name, price) VALUES (?, ?)";

        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, item.getName());
            stmt.setDouble(2, item.getPrice());
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void removeMenuItem(MenuItem item) {
        String sql = "DELETE FROM Menu WHERE id = ?";

        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setInt(1, item.getId());
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void updateMenuItem(MenuItem item) {
        String sql = "UPDATE Menu SET name = ?, price = ? WHERE id = ?";

        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, item.getName());
            stmt.setDouble(2, item.getPrice());
            stmt.setInt(3, item.getId());
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}
```

#### User 类和 Authentication 类

```java
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class Authentication {
    private Connection conn;

    public Authentication() {
        try {
            this.conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/your_database_name", "username", "password");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public boolean authenticate(String username, String password) {
        String sql = "SELECT * FROM Users WHERE username = ? AND password = ?";

        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, username);
            stmt.setString(2, password);
            ResultSet rs = stmt.executeQuery();

            return rs.next();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return false;
    }

    public boolean isAdmin(String username) {
        String sql = "SELECT isAdmin FROM Users WHERE username = ?";

        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, username);
            ResultSet rs = stmt.executeQuery();

            if (rs.next()) {
                return rs.getBoolean("isAdmin");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return false;
    }
}
```

#### Order 类

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

public class Order {
    private List<MenuItem> items;
    private double total;
    private boolean isPaid;

    public Order() {
        this.items = new ArrayList<>();
        this.total = 0.0;
        this.isPaid = false;
    }

    public void addItem(MenuItem item) {
        items.add(item);
        total += item.getPrice();
    }

    public void removeItem(MenuItem item) {
        items.remove(item);
        total -= item.getPrice();
    }

    public double calculateTotal() {
        return total;
    }

    public void setPaid(boolean paid) {
        isPaid = paid;
    }

    public boolean isPaid() {
        return isPaid;
    }

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

#### Main 类

```java
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Menu menu = new Menu();
        Authentication authentication = new Authentication();
        Order order = new Order();
        Scanner scanner = new Scanner(System.in);

        System.out.println("欢迎使用点餐系统！");
        boolean loggedIn = false;
        String username = "";

        while (!loggedIn) {
            System.out.print("请输入用户名：");
            username = scanner.nextLine().trim();
            System.out.print("请输入密码：");
            String password = scanner.nextLine().trim();

            loggedIn = authentication.authenticate(username, password);
            if (!loggedIn) {
                System.out.println("登录失败，请重新输入用户名和密码。");
            }
        }

        boolean isAdmin = authentication.isAdmin(username);

        while (true) {
            displayMenu(menu);

            System.out.print("请输入菜品名称添加到订单（输入0结算）：");
            String userInput = scanner.nextLine().trim();

            if (userInput.equals("0")) {
                break;
            }

            MenuItem menuItem = menu.getMenuItemByName(userInput);
            if (menuItem != null) {
                order.addItem(menuItem);
                System.out.println(menuItem.getName() + " 已添加到订单！");
            } else {
                System.out.println("抱歉，菜品不存在，请重新输入。");
            }
        }

        // 结算订单
        System.out.println("\n订单详情：");
        for (MenuItem item : order.getItems()) {
            System.out.println(item.getName() + "\t￥" + item.getPrice());
        }
        System.out.println("总计：￥" + order.calculateTotal());

        // 支付处理
        System.out.print("请选择支付方式（1.支付宝 2.信用卡）：");
        int paymentMethod = scanner.nextInt();
        scanner.nextLine(); // 消耗换行符

        // 模拟支付过程
        System.out.println("支付中...");
        // 这里可以添加具体的支付处理逻辑，例如调用支付接口等

        order.setPaid(true);
        System.out.println("支付成功！谢谢使用，再见！");
    }

    private static void displayMenu(Menu menu) {
        System.out.println("\n菜单列表：");
        for (MenuItem item : menu.getMenuItems()) {
            System.out.println(item.getName() + "\t￥" + item.getPrice());
        }
    }
}
```