update additional fields in the mapping table using hibernate

Question

I have user table with user.hbm.xml and department table with department.hbm.xml. mapping table is userdepartment with user_id and department_id columns. The mappings are automatically populated through foreign key definitions. I would like to have additional columns in this mapping table that tracks, who changed the mapping, comments etc. How can I update these additional columns? Do I need userdepartment.hbm.xml for this and a mapping class? Is there a way to map these additional columns to main classes? Pls advice.

Answer 1

If the join table has other columns than just the two foreign keys, then it's not a join table anymore, but an entity in itself.

You should thus have an additional Participation entity, containing the information about the participation of a user in a department, and have a OneToMany between User and Participation, and a OneToMany between Department and Participation.

Treat the Participation entity like all the other entities: it should have a single-column auto-generated ID, and two join columns. To make sure the same user doesn't participate twice for the same department, add a unique constraint on [userId, departmentId] .