We are automating generation of our persistence classes against an existing database schema. The results are value objects. We put our business logic in extensions of the generated classes. The extensions have no persisted state themselves and no associated table. However, those are the objects we instantiate. How do we persist the extensions?

Leaning toward velocity script to generate one class that merges the hard-carved extensions with the automatically generated value objects. Hoping there is a simpler strategy.

why not have hbm2java make you an abstract class with the value properites and then let you extend it to implement the biz-methods ?

Then you can easily regenerate again and again as the hbm2java will only override the abstract class ?

Add a <meta attribute="generated-class">AbstractXXX</meta> to the class mapping and you will get it.

...and hbm2java handles all the messy stuff about handling the correct generation of associations and proper inheritance etc. when you have subclasses ....

[quote="max"]why not have hbm2java make you an abstract class with the value properites and then let you extend it to implement the biz-methods? quote]

Sounds like a great idea. This allows you to decide at runtime what type to instantiate provided it extends the abstract class specified in the ORM file. Many important applications for this in terms of customizing runtime behavior.

I don't think you are following me (or i ain't following you ;)

The hbm2java feature allows it to generate a AbstractXXX where you mention XXX in the mapping file.

Thus you only basically write "class XXX extends AbstractXXX { ... }" and when the hbm2java is rerun it will only redo AbstractXXX.

The mapping file will still map to the concrete class.

I follow you now. The meta tag overrules the name of the generated class without messing with the mapping at all. There is no "abstract" in a literal sense. This is precisely what I was looking for.

Thanks!

There is no input box for the "generated-class" meta tag in the middlegen GUI. I should be able to doctor the velocity script to include that meta tag at the top of each class.

yes - should be trivial (even though not as nice as it would create an abstract class for all your classes even though you might need it for all).

Oh well ,*)

I should probably download the plug-in source to see where you specify your own velocity script but perhaps you know off the top of your head. Meanwhile I am unzipping the plug-in jar, updating hibernate.vm, then zipping it back up again. A little clunky but at least I get automatic meta tags for generated-class.