detached entity passed to persist when using RequestFactory

I'm trying to use the RequestFactory but I have trouble changing existing records. I keep getting a org.hibernate.PersistentObjectException: detached entity passed to persist while I do not understand what's wrong.

I have a the following class:

@Service(Product.class)
public interface ProductRequest extends RequestContext {

    Request<Long> countProducts();

    Request<ProductProxy> findProduct(Long id);

    Request<List<ProductProxy>> findAllProducts();

    InstanceRequest<ProductProxy, Void> persist();

    InstanceRequest<ProductProxy, Void> remove();

}

I have a function that lists all products (retrieved via findAllProducts()) and then I want to change one product. For this purpose I use the following code:

public void changeProductDetails(ProductProxy prod) {
        ProductRequest newProductRequest = MyApplication.getRequestFactory().productRequest();
        ProductProxy editedProduct = newProductRequest.edit(prod);
        editedProduct.setPurpose("new purpose string");
        newProductRequest.persist().using(editedProduct).fire(new Receiver<Void>() {
            @Override
            public void onSuccess(Void arg0)
            {
                System.out.println("Product changed开发者_Python百科");
            }
        });
    }

What is wrong, is that persist should not be called to detached objects. Purpose of persist-method is to persist new objects.

What you want to do is to merge changes from the detached object. That is done via method named merge in Hibernate/JPA.