Re: [aspectj-users] Q about "adviceexecution" and "declare error"

[Matthew Webster <matthew_webster@xxxxxxxxxx>]

Eric,

I was aware of the work on open modules
but have not read the papers you refer to. Perhaps I should. However I
do not believe any new controls are necessary because Java in conjunction
with a runtime modularity framework like OSGi already provides sufficient
mechanisms. This is why I am working on AOSGi (http://www.eclipse.org/equinox/incubator/aspects/).


>I know whole research communities which believe
that not being able to
>guarantee any sort of encapsulation by far the largest problem of
>AspectJ.
I not believe AspectJ breaks encapsulation
any more than Java reflection.

Matthew Webster
AOSD Project
Java Technology Centre, MP146
IBM United Kingdom Limited
Hursley Park, Winchester,  SO21 2JN, England
Telephone: +44 196 2816139 (external) 246139 (internal)

"Eric Bodden" <eric.bodden@xxxxxxxxxxxxxx>
Sent by: aspectj-users-bounces@xxxxxxxxxxx

22/02/2007 15:05

Please respond to
aspectj-users@xxxxxxxxxxx

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Subject	Re: [aspectj-users] Q about "adviceexecution" and "declare error"

Hmmm, so you don't believe the entire body of works
on open modules then?

http://citeseer.ist.psu.edu/aldrich04open.html
http://doi.acm.org/10.1145/1119655.1119664

Note that those works propose both, aspects which a module is
"protected" from as well as aspects which deliberately break
this
encapsulation, e.g. for the purpose of debugging.

I know whole research communities which believe that not being able to
guarantee any sort of encapsulation by far the largest problem of
AspectJ.

Eric

On 2/22/07, Matthew Webster <matthew_webster@xxxxxxxxxx> wrote:
>
> Dean,
>
>
>  I'm working on idioms for defining PCDs that a class developer
can use to exclude join points from possible advices. For example, say
I want a 'critical section' to never be advised.
>
> Requests to allow  the author of a class to say "don't weave
my code" crop up quite regularly. They come in a number of forms e.g.
https://bugs.eclipse.org/bugs/show_bug.cgi?id=47919. Unfortunately such
a feature is incompatible with AOP and I distinctly remember Gregor Kiczales
talking on the subject in his keynote at AOSD 2003. If a single join point
becomes off limits to an aspect there is a risk that it won't work and
hence will be invalid. The false assumption is that the consequences of
weaving the code will always be worse than not weaving it. For example
one of the many compelling use cases for AOP is in-field problem diagnosis
and the feature you are suggesting would turn "protected" code,
that would start off as one or two methods but would quickly end up as
whole applications when the capability is abused, into a black hole.
>
> Knowing whether your code is being advised is a different matter.
For this reason we have worked on the Cross-cutting Comparison view in
AJDT and extensive messages on other diagnostics for LTW. You can't stop
the modification of an open byte-code format so in my view its better to
let someone do it with AspectJ, which allows them to express themselves
at the right level and hence is less prone to error, than something that
operates at a much lower level.
>
> Matthew Webster
>  AOSD Project
>  Java Technology Centre, MP146
>  IBM United Kingdom Limited
>  Hursley Park, Winchester,  SO21 2JN, England
>  Telephone: +44 196 2816139 (external) 246139 (internal)
>  Email: Matthew Webster/UK/IBM @ IBMGB, matthew_webster@xxxxxxxxxx
>  http://w3.hursley.ibm.com/~websterm/
>
>
>
>  "Ron Bodkin" <rbodkin@xxxxxxxxxxxxxx>
> Sent by: aspectj-users-bounces@xxxxxxxxxxx
>
> 21/02/2007 17:30
>
> Please respond to
>  aspectj-users@xxxxxxxxxxx
>
>
> To <aspectj-users@xxxxxxxxxxx>
>
> cc
>
>
> Subject RE: [aspectj-users] Q about "adviceexecution" and
"declare error"
>
>
>
>
>
>
>
>
> Hi Dean,
>
> The declare error doesn't apply because the advice is dispatched from
those methods but it isn't executed within them. You are asking for a new
pointcut, say advised, that is to adviceexecution as call is to execution
(modulo the difference between implicit and explicit dispatch).
>
>
>  ________________________________

> From: aspectj-users-bounces@xxxxxxxxxxx [mailto:aspectj-users-bounces@xxxxxxxxxxx]
On Behalf Of Dean Wampler
>  Sent: Tuesday, February 20, 2007 12:07 PM
>  To: aspectj-users@xxxxxxxxxxx
>  Subject: Re: [aspectj-users] Q about "adviceexecution"
and "declare error"
>
> Ron Bodkin wrote:
> Indeed, you would want a withinadvice pointcut, but failing that you
might just refactor to expose the relevant code as a method. Of course,
to have something like withinadvice be useful, I'd want AspectJ to have
better matching on advice signatures too (so you could say adviceexecution(before(int,
String))).
> Agreed.
>
>  What I ended up doing was writing a PCD that looks something
like this:
>
>      cflow(execution(* MyClass.myRestrictedMethod(..))
&& adviceexecution() && !within(ProhibitAdvice+)
>
>  (ProhibitAdvice is the aspect...)
>
>  Then I used before advice to throw an exception. Again, my particular
goal is to prevent any advice from being invoked within the execution context
of "myRestrictedMethod()".
>
>  Here's what I find perplexing. The following does nothing:
>
>  declare error: withincode(* MyClass.myRestrictedMethod(..))
&& adviceexecution(): "message";
>
>  Looking at the AJDT adornments, it's clear that advice is being
applied within the method, from another aspect designed to trigger the
error (the adornment doesn't have a '?' on it ;). What am I missing? I
thought of precedence, but experiments there didn't do anything.
>
>  Thanks,
>
>  dean
>
>
>
>  ________________________________

> From: aspectj-users-bounces@xxxxxxxxxxx [mailto:aspectj-users-bounces@xxxxxxxxxxx]
On Behalf Of Dean Wampler
>  Sent: Tuesday, February 20, 2007 8:35 AM
>  To: aspectj-users@xxxxxxxxxxx
>  Subject: Re: [aspectj-users] Q about "adviceexecution"
and "declare error"
>
> Thanks, Ramnivas,
>
>  I was under the mistaken impression that adviceexecution works
something like a "withincode" or "cflow", which of
course it doesn't.
>
>  dean
>
>  Ramnivas Laddad wrote:
> Dean,
>
>  Since adviceexecution() will match an advice join point and
criticalSectionPCD() will match a non-advice join point (in your case,
I presume you are selecting execution() or call() join point), combining
the corresponding pointcuts using && will match nothing.
>
>  -Ramnivas
> On 2/20/07, Dean Wampler <dean@xxxxxxxxxxxxxxxxxxxxx> wrote:
> I'm working on idioms for defining PCDs that a class developer can
use to exclude join points from possible advices. For example, say I want
a 'critical section' to never be advised.
>
>  What I've tried is something like the following:
>
>  declare error: criticalSectionPCD() && adviceexecution():
"Can't advise the critical section."
>
>  This compiles fine, but it has no effect. (I defined another
aspect that breaks the rule.)
>
>  Suggestions?
>
>  dean
>
>
>
>
>
>   ________________________________

>
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> --
>
>
>
> Dean Wampler, Ph.D.
>  dean at aspectprogramming.com
>  objectmentor.com
>  aspectprogramming.com
>  contract4j.org
>
>  I want my tombstone to say:
>
>
>
> Unknown Application Error in Dean Wampler.exe.
>  Application Terminated.
>
> Okay
> Cancel
>
>
>
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-- 
Eric Bodden
Sable Research Group
McGill University, Montréal, Canada
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