Thank you Patrick for your quick response but unfortunately that is not the problem because, as I already wrote, I do everything by the book (tutorial) so I did use Set instead of HashSet
If I understood correctly I can do following (has to do with AbstrFile class previously explained:
how AbstrFile is created is not important and assume
that session is an instance of Hibernate session
and all AbstrFile instances will be saved to database???
There is no need to save each one but it is sufficient to save parent???
This is how I do this in my code. And I did cascade all operations.
thanks again