I have the follow scenario:

I have a user, this user can belogs to one or more systems and can have one profile in each system.

My database tables are:

user
profile
system
detail

and my entities are:

User
Profile
System
Detail

The Detail entity holds reference to 3 others entities: User, Profile and System and i have a Detail set in Usuario entity (eg. Usuario.setDetails).
Right now i don't know if this is the correct way to do the things, i'm almost going to solve this problem in SQL, but i'm asking for some advice here before do it in SQL.

Why don't you drop "Detail" from this and view the Profile entity as a many-to-many relationship with User and System. The you can map User with Profile with a Hibernate's one-to-many, and a Profile with a system with a many-to-one. I think you could then put a natural-id around the definitions in "profile" so that Hibernate puts a unique constraint and forces to have only one Profile for each User-System pair.

With your sugestion i can do something like this:

User 1 -> System 1-> Profile 1
and
User 1 -> System 2-> Profile 1 ?

Note the same profile can be shared with diferent systems.
This code belongs to a webapp that controls the users in a Single Signon System. Once the user is logged he has diferent profiles in each system under Single Signon.

Then it could be like this:

User ---one-------many---> Profile <---many-------many---> System

See Hibernate reference docs to check how to define a many to many relationship (which will involve a profile_system table).

Then when i add a new User i'll do this:

Profile profile = new Profile();
profile.setSystem(systemInstance);
//profile is an ArrayList used in a JSF component
profiles.add(profile);
User user = new User();
//user.setProfiles(Set profiles) is my setter of profiles Set
user.setProfiles(new HashSet(profiles));
session.save(user);

right?

How is the tables structure in this sugestion?

Who will store the UserId? The profile_system table? I mean i need retrieve a list of Profiles from User entity how this can be done without a UserId in profile_system table, if i put the UserId in profile table the profile will not shared with other systems.