子类的Hibernate映射表

Question

I have 3 classes:

Person {
    int id;
    String name;
    String lastName;
}

Employee extends Person {
    //some additional data
}

Owner extends Person {
    //some additional data
}

For each class I have separate table. In Employee table the key should be exactly the same as in Person table.

And now when I insert Employee class there should be one record in Person table, one in Employee with the same ID (lets assume this is value 1).

After that I want to insert Owner class and I want it to be the same Person (ID=1) so after inserting Owner It should be added only one record in table Owner, but record in table Person should be left as it is.

I have tried this: http://viralpatel.net/blogs/hibernate-inheritance-table-per-subclass-annotation-xml-mapping/

Inserting first class is OK, inserting second with diffrent ID is ok, getting objects from db is ok, but whet I want to add Owner class with the same ID such as the existing person I got hibernateException... Can anyone help me?

Answer 1

It's plain impossible. Since Java only has single inheritance, an object can't be both an employee and an owner. You shouldn't use inheritance to map these associations.

Instead, you should have Person have a OnetoOne association with its Employee role, and a OnetoOne association to its Owner role.

Answer 2

"It's plain impossible." In my code example Employee extends Profile and Owner exstends Profile.

If I understend corectlly you anwser you suggest something like this:

Person{
Employee emp;
Owner owner;
}

In my first class hierarhy I was able to do:

Person getPersonFromDb( Class class, int id){  ...  session.get(class, id) ... }

Owner o = (Owner) getPersonFromDb(Owner.class, id);
Employee e =(Employee) getPersonFromDb(Employee.class, id);

In your approach I can't have something like this...