For educational purposes, I’m developing a simple desktop/console Java program to persist data into MySQL database. I’d like to know if the following architecure/layers are ok (despite the computational/maintenance cost, interpretability etc):

Class Product

public class Product {
    private int id;
    private String name;
    
   //getters and setters and constructors
}

ConnectionFactory:

public abstract class ConnectionFactory {
     private static Connection conn  = null;


    public  static Connection getConnection() throws SQLException{
        if (conn == null)
               conn = DriverManager.getConnection("jdbc:mysql://localhost/database_name","user","password");

        return conn;
    }
}

Interface DAO

public interface DAO <T>{
     void  save(T type);
     List<T> findAll();

}

Interface ProductDAO

public class ProductDAO implements DAO<Product>{
    @Override
    public void save(Product p) {
        String sql = "INSERT INTO product values (?,?)";

        try(Connection con = ConnectionFactory.getConnection();
            PreparedStatement stmt = con.prepareStatement(sql)) {
            stmt.setInt(1, p.getId());
            stmt.setString(2, p.getName());
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }


    @Override
    public List<Product> buscarTodos() {
        String sql = "SELECT * FROM product";
        List<Product> listProd =new ArrayList<>();
        try(Connection con = ConnectionFactory.criaConexao();
            PreparedStatement stmt = con.prepareStatement(sql))  {
            ResultSet rs = stmt.executeQuery();
            while (rs.next()) {
                Product p = new Product(rs.getInt("id"), rs.getString("name"));
                listProd.add(p);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return listProd;
    }
}

Interface ProductService:

public interface Service <T>{
    void  save(T type);
    List<T> findAll();
}

Class ProductService:

public class ProductService implements Service<Product>{
    ProductDAO productDAO ;

    public ProductService() {
        productDAO= new ProductDAO();
    }

    @Override
    public void save(Product p) {
        productDAO.save(p);
    }

    @Override
    public List<Product> findAll() {
        return productDAO.findAll();
    }
}

I’d be grateful for comments and suggestions.