PAT as a persistence aspect
Which AOP framework?
PAT uses JBossAOP
as the aspect framework. I've did such choice mainly because
at the time of developing AspectJ didn't have support for annotations. JBossAOP
was driven by annotations from the same beginning (I think), so the choice was
clear. Of course I knew differences between both.
The only disadvantage when developing such framework with JBossAOP is lack of
binary introductions. JBossAOP is "Java compatible", so it means any aspectized
source file must compile
with <javac> or any Java compiler. But this causes the code look ugly when
accessing introduced members (fields, methods).
AspectJ is much better option in that
Orthogonal in that particular case would mean: create any POJO
based Java model,
annotate every method that changes state of the system, annotate business
objects, and that would be all.
Annotations - social view
Use of annotations in the case of persistence is in my opinion the best choice.
It's much more better from the social view, than from technical one.
The user of PAT - a programmer - sees where the
control flow of its application is changed - where the data is stored.
It is more safe this way, than
traditional regular-expression-pointcut-style. It is not exclusive way, though.
If one needs, one may define pointcuts using regular expression style (in a
separate XML file) - no problem at all.
What about the aim of orthogonality?
Well, it almost worked out. Almost, because there are some requirements to the
model when designing it:
In general PAT will not work correctly
when passing an object
indirect reference to a BO
and not being BO itself - to a transaction
Whether it is rare case or not, it can be solved by just creating additional,
short wrapper class.