Need help with Hibernate? Read this first:
http://www.hibernate.org/ForumMailingli ... AskForHelp

Hibernate version:
3.2

Suppose i've this schema (reduced for clear read):

create table `articles` (art_id INTEGER prymary key, art_data date)
create table `registrations` (art_id INTEGER, reg_id integer, reg_value NUMERIC, PRIMARY KEY(art_id, reg_id))

how can i map the primary key of the register?
I do:


but when i call session.persist(article)

i receive a exception that the registration have same id of anothewr registration i suppose because the "id" property is null and the hashCode of Registrazione.Id is the same.

in which way i can do this mapping? i had to add another field to registrations table?

You don't need another field. You just need to set all parts of the primary key so that the combined values are unique for each row that you want to add to the table.