9.10

[实验任务二]：单一职责原则

登录模块在实际项目开发中很常见，请按照教材28页（PPT49页）利用单一职责原则重构后的类图实现这一模块。

实验要求：

1.提交源代码和对应的数据库文件（注意将此模块保存，以备以后使用）；

2.注意编程规范。

1.User.java
public class User {
    private String username;
    private String password;

    public User(String username, String password) {
        this.username = username;
        this.password = password;
    }

    // Getters and Setters
}

2.UserRepository.java
import java.sql.*;

public class UserRepository {
    private Connection connection;

    public UserRepository(Connection connection) {
        this.connection = connection;
    }

    public User findUserByUsername(String username) {
        try {
            PreparedStatement stmt = connection.prepareStatement("SELECT * FROM Users WHERE username = ?");
            stmt.setString(1, username);
            ResultSet rs = stmt.executeQuery();

            if (rs.next()) {
                return new User(rs.getString("username"), rs.getString("password"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
}

3.AuthService.java
public class AuthService {
    private UserRepository userRepository;

    public AuthService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public boolean login(String username, String password) {
        User user = userRepository.findUserByUsername(username);
        return user != null && user.getPassword().equals(password); // 简化示例，真实应用中应使用哈希密码
    }
}

4.LoginController.java
public class LoginController {
    private AuthService authService;

    public LoginController(AuthService authService) {
        this.authService = authService;
    }

    public void handleLogin(String username, String password) {
        if (authService.login(username, password)) {
            System.out.println("登录成功！");
        } else {
            System.out.println("登录失败，用户名或密码错误。");
        }
    }
}

5.数据库文件 (SQL)
CREATE DATABASE UserDB;

USE UserDB;

CREATE TABLE Users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    password VARCHAR(255) NOT NULL
);