In the application I'm developing the user can add relations to the database. There are different kinds of relations, such as:

Customer
Distributor

Besides the differences, there are a couple of things that are similair. That's why I created a structure like this:



In the mapping-file I used the joined-subclass for this:



But sometimes a customer is also a distributor. In a situation like that, I need to create a Customer and a Distributor object and the ids need to be the same. Hibernates needs to see that the superclass of the two objects (the Relation data) are in fact the same object. In the database the records should be:

Table Relation
relationId: 1
name: Some Company

Table Customer
relationId: 1
invoiceAddress: Some Street

Table Distributor
relationId: 1
contractPeriod: 1 year

The problem is that when I add the Customer object first, I can't save the Distributor object with the same id. When I save it, Hibernate generates an unique id. When I save the Relation-object first and then try to save the customer or distributor, Hibernate first checks if there is an object in cache that corresponds to the RelationId. This is the case because I saved the Relation object, so it returns this Relation object.

So, how can I save these two objects of different types and that Hibernate sees that the superclass of the two objects are the same and doesn't need to be resaved? It is necessairy that the two ids stay the same.

Almost the same problem as http://forum.hibernate.org/viewtopic.php?t=940671

I didn't see that one. Stood a bit low in the search results. I'll wait until there is an acceptable answer there.

Thanks

I don't think that your solution is possible. What should Hibernate return when you make a query against the super class? Instances of Customer or instances of Distributor? If you would make a query against Customer and one against Distributor you would suddenly hafe two different objects that mean the same.

I think you should really do it that way: Make Customer and Distributor contain an Relation. If thats not enoug, make an Interface with the Methods of Relation und make Customer and Distributor implement it and return the values of the method of the Relation that they contain.

I use query by example, so if I would request a Distributor, I'll get that one. That confusement wouldn't be an option in our application.


The reason why we choose Hibernate was that we wanted to program our business logic in the way we felt best and we didn't want our business logic to depend on how we would setup our database.

But I did find a solution. First I add the Relation-object


After that I evict the relation out of the session:


I manually added a record to the database for the Distributor and the Customer:


Then I clear the session, set the relationId, find the customer, set the values and update the object: