数据库访问通用类

public class UserDAO {
    private Connection getConnection() throws SQLException {
        // 获取数据库连接
    }

    public User getUserById(int id) {
        String sql = "SELECT * FROM users WHERE id = ?";
        try (Connection conn = getConnection();
             PreparedStatement ps = conn.prepareStatement(sql)) {
            ps.setInt(1, id);
            try (ResultSet rs = ps.executeQuery()) {
                if (rs.next()) {
                    return new User(rs.getInt("id"), rs.getString("name"));
                }
            }
        } catch (SQLException e) {
            // 处理异常
        }
        return null;
    }
}

public void addUser(User user) {
    String sql = "INSERT INTO users (name, email) VALUES (?, ?)";
    try (Connection conn = getConnection();
         PreparedStatement ps = conn.prepareStatement(sql)) {
        ps.setString(1, user.getName());
        ps.setString(2, user.getEmail());
        ps.executeUpdate();
    } catch (SQLException e) {
        // 处理异常
    }
}