public List<Product> listProductById(int id) {
   return productDAO.listProductById(id);
 }
  @Transactional
  public List<Product> listProduct() {

    return productDAO.listProduct();
  }
 @Transactional
 public void removeProduct(Integer productId) {
   productDAO.removeProduct(productId);
 }
 @Transactional
 public void addProduct(Product product) {
   productDAO.addProduct(product);
 }