RE: [aspectj-users] Implementing abstract pointcut that includesnojoinpo

["Ron Bodkin" <rbodkin@xxxxxxxxxxxxxx>]

I found the ability to specify empty pointcuts that some concrete aspects
can override helpful in the glassbox inspector project. I use pointcuts to
indicate common idioms for MVC frameworks (like class controllers and method
signature or method name controllers), so implementations (monitors for
Spring, Struts, Axis) can just extend pointcuts for the cases that apply to
them. This really helped keep modular code when using the worker object
pattern, and it is nice to not have to explicitly indicate the cases that do
not apply. I will be discussing this more in part two of my article at the
AOP@Work article series at IBM Developerworks (stay tuned!)

-----Original Message-----
From: aspectj-users-bounces@xxxxxxxxxxx
[mailto:aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Ken Pelletier
Sent: Friday, October 21, 2005 6:05 AM
To: aspectj-users@xxxxxxxxxxx
Subject: Re: [aspectj-users] Implementing abstract pointcut that
includesnojoinpoints

Thanks for all the quick replies.

Oddly, I did try the pointcut with not spec:

protected pointcut overriddenAbstractPointcut();

But because I'd missed on the parameter matching (the abstract decl  
captures the target for around advice which I'd left off in the sub),  
I mistakenly thought that the syntax was generally incorrect.

So, it's actually the first thing that came to mind, which is always  
a good feeling.

It's also good to see that this can be done in the base aspect; sort  
of a parallel with the template method pattern, only for pointcuts  
and advice.  Good stuff.

Thanks,

- Ken

On Oct 21, 2005, at 12:24 AM, Ron Bodkin wrote:

> Ken,
>
> This syntax will do it, although it is a little counterintuitive  
> when you
> first encounter it:
>
> protected pointcut overriddenAbstractPointcut();
>
> You can also define a default empty value in a concrete pointcut  
> (like this)
> in an abstract aspect and then override it with a non-empty  
> definition in
> some concrete aspects. E.g.,
>
> abstract aspect Base {
>    protected pointcut optionalPoint(); // empty
> }
>
> aspect Derived1 extends Base {
>    protected pointcut optionalPoint() : within(foo..*); // defines  
> for this
> }
>
> aspect Derived2 extends Base {
>    // optional is empty for this concrete aspect
> }
>
> -----Original Message-----
> From: aspectj-users-bounces@xxxxxxxxxxx
> [mailto:aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Ken Pelletier
> Sent: Thursday, October 20, 2005 10:06 PM
> To: aspectj-users@xxxxxxxxxxx
> Subject: [aspectj-users] Implementing abstract pointcut that includes
> nojoinpoints
>
> I have an abstract aspect that declares a couple of abstract
> pointcuts to be overridden in concrete subclasses.
>
> In a particular subclass, however I want to nullify one of those
> pointcuts; include no joinpoints at all.
>
> Is there a common idiom for implementing a concrete pointcut that
> explicitly includes no joinpoints?
>
> I know I can nullify with && if(false), but it smells funny to
> declare any advice type at all if really none applies.
>
> Eg:
>
> protected overriddenAbstractPointcut() :
> <what_would_advice_spec_be_here> && if(false;
>
> Regards,
>
> - Ken
>
> PS: it's probably a design smell in the first place to have abstract
> pointcuts that sometimes have no applicable concrete implementation,
> but that's another matter.  :-)
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