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Hibernate version: 3.0.5

I was wondering if anyone ever had to do the following :

Standard product, using Hibernate, with let's say 20 classes mapped and defined.

Need to customize the product often, creating custom subclasses of the original classes - which usually have an extended database table.

So let's say I have StandardObject, which is mapped and works correctly, and CustomObject which extends StandardObject.

I'm really trying to understand how I can make a mapping for CustomObject which extends and substitutes the original mapping, so that a query like "from StandardObject" actually retrieves instances of CustomObject.

It's a pattern we had in the previous framework, called substitution - usually managed by a configured factory.

I hope there is some solution...

Thanks in advance,

Giulio

Did you have a look at the subclass strategies ?

You could create your new CustomObject extending StandardObject as expected and then create a mapping file using


or


instead of the <class> tag.

Read carefully the doc's chapter 10:

http://www.hibernate.org/hib_docs/v3/re ... strategies

Hi lorban,

I carefully looked at the feature you mentioned, and I even wrote a testcase.

The <subclass> approach is useful when subclasses of a superclass live together in the table. My situation is different : the subclass (only one exists) SUBSTITUTES the superclass.

I would except then the persistence layer to retrieve instances of the substitute and not of the original class, if a manner to do so exists.

Any idea ?

You could probably achieve that using filters:

http://www.hibernate.org/hib_docs/v3/re ... te-filters

You would have to create a "type" column in the parent's table in case of a <joined-subclass> mapping or re-use the discriminator for a <subclass> one.

Actually my pattern has no joined-subclasses or discriminator.

The table is the same, the subclass would substitute interely the superclass.

I think the entity-name attribute in <class> mapping is the most near solution.


Thanks,

Giulio