[hibernate-dev] Hibernate.next version and AS 7.2 community release...

[Hardy Ferentschik]

On Jun 26, 2012, at 9:02 PM, Sanne Grinovero wrote:

> There are a lot of libraries depending on Hibernate Commons
> Annotations, up to Infinispan for the Query module (not depending on
> any other Hibernate core library).
> 
> If you want to rewrite it's internals and provide a drop-in
> replacement, that's nice. But I see no reason to throw it away?

Sure, here we go. 

Commons Annotations tries to do two things at the same time. 

First there is the annotation abstraction, hiding the fact whether an annotation is an actual annotation 
or a corresponding xml configuration element. It does this  by introducing XClass & Co. 
And that's the first rub. Working with XClass is highly confusing. You never know whether you
deal w/ an XClass or an actual Class instance. Working on the ORM annotation processing code you have often
have methods you get one or the other. Confusing! 

Also, working with Jandex you get the actual annotation vs xml configuration much easier. Jandex itself abstracts already an annotation. 
Hence you just have to implement  the right Jandex classes to create pseudo annotation (annotation backed by xml configuration). Using Jandex
in combination with Commons Annotations would mean you would abstract the abstraction.

Back to the two things Commons Annotation tries to do. Commons Annotation also does generic type resolution.
IMO this two things should be separate. There is annotation processing and there is type resolution. I often don't need 
both, but just one of them. Using a library like classmate can easily do the type resolution when I need it in a much more
transparent way. The code is actually easily understandable. It is much harder to understand how the corresponding Commons Annotation
code works.

Regarding your reinventing the wheel argument. The metamodel branch already successfully removed the Commons Annotation
dependency. Jandex offers all we need and Strong implemented some classes which create pseudo 
annotations for the xml config. The type resolution was replaced by classmate. Bottom line is that Commons Annotations is already 
replaced on the metamodel branch.

Last but not least, I am definitely not the guy who wants to rewrite working just for the sake of it. However, if I see that there are better
alternatives for existing code which results in easier to understand code I go for it.

--Hardy