UserDAO.java

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDAO {

    public boolean registerUser(User user) {
        try (Connection conn = DBConnection.getConnection()) {
            String query = "INSERT INTO users (username, password, email) VALUES (?, ?, ?)";
            PreparedStatement stmt = conn.prepareStatement(query);
            stmt.setString(1, user.getUsername());
            stmt.setString(2, user.getPassword());
            stmt.setString(3, user.getEmail());
            return stmt.executeUpdate() > 0;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    public User loginUser(String email, String password) {
        try (Connection conn = DBConnection.getConnection()) {
            String query = "SELECT * FROM users WHERE email = ? AND password = ?";
            PreparedStatement stmt = conn.prepareStatement(query);
            stmt.setString(1, email);
            stmt.setString(2, password);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                User user = new User();
                user.setId(rs.getInt("id"));
                user.setUsername(rs.getString("username"));
                user.setEmail(rs.getString("email"));
                return user;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    public boolean usernameExists(String username) {
        try (Connection conn = DBConnection.getConnection()) {
            String query = "SELECT * FROM users WHERE username = ?";
            PreparedStatement stmt = conn.prepareStatement(query);
            stmt.setString(1, username);
            return stmt.executeQuery().next();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    public boolean emailExists(String email) {
        try (Connection conn = DBConnection.getConnection()) {
            String query = "SELECT * FROM users WHERE email = ?";
            PreparedStatement stmt = conn.prepareStatement(query);
            stmt.setString(1, email);
            return stmt.executeQuery().next();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
}