软件开发中的 DTO 和 DAO

<code class="java">public class UserDTO {
    private String username;
    private String email;

    public UserDTO(String username, String email) {
        this.username = username;
        this.email = email;
    }

    // getters and setters
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }
}</code>

<code class="java">import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class UserDAO {
    private Connection connection;

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

    public UserDTO getUserById(int id) throws Exception {
        String query = "SELECT username, email FROM users WHERE id = ?";
        PreparedStatement statement = connection.prepareStatement(query);
        statement.setInt(1, id);
        ResultSet resultSet = statement.executeQuery();

        if (resultSet.next()) {
            String username = resultSet.getString("username");
            String email = resultSet.getString("email");
            return new UserDTO(username, email);
        }
        return null;
    }

    public void saveUser(UserDTO user) throws Exception {
        String query = "INSERT INTO users (username, email) VALUES (?, ?)";
        PreparedStatement statement = connection.prepareStatement(query);
        statement.setString(1, user.getUsername());
        statement.setString(2, user.getEmail());
        statement.executeUpdate();
    }
}</code>

<code class="java">public UserDTO getUserDetails(int id) {
    return userService.getUserById(id);
}</code>

<code class="java">public UserDTO getUserById(int id) {
    return userDAO.getUserById(id);
}</code>