well, I create JPA Entities that maps the JDBC realm tables..
I used the table definitions of this blog:
http://blogs.sun.com/swchan/entry/jdbcrealm_in_glassfish
about your questions:
> - I guess all columns (username, password, groupname) have to be Strings, right?
yes
> - Any min./ max. length restrictions?
no idea, but it should be flexible since the container seems to not
apply any constraints verification
> - Does the user table have to have a foreign key column for the group table?
no, and that's weird for me.. but, it is NxN relationship anyway..
someone better in DB may help..
> - How will the group table be used?
The Group == roles
> - What about roles? (It's not the same as a group, right?)
it is the same (same usage I mean)
> - What should I set to: (Note I translated the names to English myself, so maybe they are not 100% equal. How can change the language of the Glassfish Admin Console to English?):
> -- Assign Group: What is this used for? What should I set here?
leave blank
> -- DB user: when is this needed?
leave blank
> -- DB password: when is this needed?
leave blank
> -- Digest-Algorithm: What is the default if empty? MD5? What do you recommend?
MD5
> -- Encoding: What is the default if empty? What do you recommend?
leave blank
> -- Character set: What is the default if empty? What do you recommend?
leave blank
> Probably I have to enable the SecurityManager, too, right? Do you recommend to activate the protocolling, too?
yes, you need to activate the security (please check the glassfish
manual for all details)