MySQL と Java を使用してシンプルなオンライン旅行予約システムを開発する方法

CREATE TABLE products (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(50) NOT NULL,
    description VARCHAR(255),
    price DECIMAL(8, 2) NOT NULL
);

CREATE TABLE users (
    id INT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(50) NOT NULL,
    password VARCHAR(50) NOT NULL,
    email VARCHAR(50) NOT NULL
);

CREATE TABLE orders (
    id INT PRIMARY KEY AUTO_INCREMENT,
    product_id INT NOT NULL,
    user_id INT NOT NULL,
    quantity INT NOT NULL,
    total_price DECIMAL(8, 2) NOT NULL,
    order_date DATE NOT NULL,
    FOREIGN KEY (product_id) REFERENCES products(id),
    FOREIGN KEY (user_id) REFERENCES users(id)
);

import java.sql.*;

public class TravelBookingSystem {
    private static final String JDBC_URL = "jdbc:mysql://localhost/travel_booking_system";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "password";

    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            connection = DriverManager.getConnection(JDBC_URL, USERNAME, PASSWORD);
            statement = connection.createStatement();
            resultSet = statement.executeQuery("SELECT * FROM products");

            while (resultSet.next()) {
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                String description = resultSet.getString("description");
                double price = resultSet.getDouble("price");

                System.out.println("Product ID: " + id);
                System.out.println("Name: " + name);
                System.out.println("Description: " + description);
                System.out.println("Price: $" + price);
                System.out.println();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (resultSet != null) resultSet.close();
                if (statement != null) statement.close();
                if (connection != null) connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.sql.*;

public class TravelBookingSystem {
    // ...

    public static void registerUser(String username, String password, String email) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;

        try {
            connection = DriverManager.getConnection(JDBC_URL, USERNAME, PASSWORD);
            preparedStatement = connection.prepareStatement("INSERT INTO users (username, password, email) VALUES (?, ?, ?)");
            preparedStatement.setString(1, username);
            preparedStatement.setString(2, password);
            preparedStatement.setString(3, email);

            preparedStatement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (preparedStatement != null) preparedStatement.close();
                if (connection != null) connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    public static void createOrder(int productId, int userId, int quantity) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;

        try {
            connection = DriverManager.getConnection(JDBC_URL, USERNAME, PASSWORD);
            preparedStatement = connection.prepareStatement("INSERT INTO orders (product_id, user_id, quantity, order_date) VALUES (?, ?, ?, CURDATE())");
            preparedStatement.setInt(1, productId);
            preparedStatement.setInt(2, userId);
            preparedStatement.setInt(3, quantity);

            preparedStatement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (preparedStatement != null) preparedStatement.close();
                if (connection != null) connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}