Suppose that i have a class User, and when someone make the login at my website, i retrieve the whole use object. Since the user already made the login, it is obviously that i want to store this User object in some way that when the user navigates through my site he remains logged.... But, it seems that when i store the user object in a session and retrieve it, the Db4o looses its reference to the real object and treats the user object retrieved from the session as a new user, meaning that if i persist this object, Db4o wont update, but create a new one... How can i solve this problem? Since Db4o team do not recommend to work wit objects internal IDs what is the recommended pattern to develop websites and pass objects between pages?

Ran into the same problem today. Your question is very enlightening as it saves me the time of actually reproducing this. It was just a hunch previous to seeing your post. Thank you. Here's hoping someone else has a good solution.

ID's (or better, UUID's) would I guess solve this. But this removes some of the type strictness in my program that was hoping to gain by using db4o in the first place.

I posted a blog post about this yesterday, the solution presented might help you.

http://db4o-tools.blogspot.com/2006...aging.html