J2EE: Storing hierarchical data

Hello,
I'm searching for the best concept of how to use and save hierarchical data
in a J2EE server.
I have a structure like a PC file system with meta data. There a folders and
files of different types. Every object have data like permissions, date and
author. And they have type-specific data fields like resolution (of an image
type) or location (of an meeting type) or ingredients (of an recipe type).
What is the best way to store that kind of data in an J2EE web application?
What database is recommendable? What concepts of persistance? Or not using
managed persistance and do it manually?

Thanks for all ideas!

Florian
.