Hello,

I have some issues with multi-level hierarchy mapping using the "Table per subclass" strategy.

Here is the list of the db tables I am trying to map using the "Table per Subclass" strategy:

4 Tables:

USER (Abstract Superclass)

EMPLOYEE (USER Subclass)

CUSTOMER (USER Subclass)

MANAGER (EMPLOYEE Subclass)

Following the principles of ERM, I should have this approach since I will need to associate MANAGER, CUSTOMER, and EMPLOYEE instances to different types of relationships table mapping them to other other entities.

I tried the "Table per Subclass" strategy from the Hibernate reference manual, and I got it to work. However, once I added a relationship to EMPLOYEE, I encountered problems. Basically, I was unable to add a <join> statement to the EMPLOYEE mapping file.

Apparently <joined-subclass> does not like <join>, hence, what am I suppose to use in replacement of <join>???

The db schema is as follows:

EMPLOYEE * == 1 EMPLOYEE_DEPARTMENT * == 1 DEPARTMENT

That is, EMPLOYEE_DEPARTMENT is a many-one relationship between the two entities EMPLOYEE and DEPARTMENT.


I tried to resolve this problem with the "Table per subclass, using a discriminator" strategy and it worked. But I had to add a discriminator to the tables. Is there any other way to accomplish this without having to deal with discriminators?

Some clarification:

The db schema is as follows (I made a mistake in the previous post):

EMPLOYEE * == EMPLOYEE_DEPARTMENT == 1 DEPARTMEN

the schema is:

(Note * denotes primary key)

EMPLOYEE(userId*, firstName, lastName, etc)

EMPLOYEE_DEPARTMENT(userId*, deptId)

DEPARTMENT(deptId*, name, etc)

Hence, EMPLOYEE_DEPARTMENT is a many-to-one mapping from EMPLOYEE to DEPARTMENT.

However, keep in mind that my question is not a DB question but rather a Hibernate mapping question. How can this mapping be done within the <joined-subclass> mapping file of EMPLOYEE?