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RE: [aspectj-users] [newbie] General help needed here.....
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Ron -
> By the way, this(Type) && execution(...) has *no* dynamic test (+),
The "this(Type)" optimization had been scheduled for some time,
so I'm glad it's in, if it is. But there is a difference between
the join points picked out by
execution(* Type.method(..))
and
execution(* method(..)) && this(Type)
Can you explain the situations where they would differ?
> for new users it's helpful to get in the mindset of
> using this to specify types instead of doing it in the method signature,
> instead of trying to remember that using declaring types with call is
> problematic and using them with execution is ok
I'm sorry but I have to disagree, if I may.
The right way to think about it is stated in the programming guide:
a pointcut signature matches a join point signature. Users, new
and experienced, will find it much easier if they follow this model
rather than the rule "always use a dynamic test and avoid
specifying the type," (particularly since that rule violates the
rule "given two pointcuts that match the same join points,
prefer the static form").
Here, the issue turns on the difference between call and execution,
which is to say the difference between the join point signature
for call and execution. The type in the method-call signature is
the compile-time type of reference being used to make the call.
The type in method-execution is the declaring type of the method
(which might not be the defining type). Understanding that gives
the developer the answer to this issue, even if they forget all else.
And following this procedure, of mentally matching the pointcut
signature to the join point signature, will work for *any*
signature-based pointcut (even in AOP systems yet-to-come).
It does mean users have to learn what the join point signatures
are. The AspectJ pointcut language is clear enough that users
can jump in and start to write code based on their guesses
about what's happening, so they (unfortunately?) get pretty far
before their guesses don't work. When they ask for help,
it's much better to point them back to the programming guide
semantic section and reinforce the idea of signature matching
than to promote an ad-hoc rule that works in some cases
for some pointcuts. As far as I'm concerned, no AspectJ
developer should ever be "in the mindset of using this to
specify types"; but they should always be in the mindset of
signature-matching for signature-based pointcuts and
instanceof (-like) tests for dynamic pointcuts, since that's
how the semantics are defined.
Sorry to go on at length. I've always found you great
about presenting AspectJ in a way users can understand,
so I hope to convince you to make this one tiny adjustment.
Thanks -
Wes
P.S. - The implementation papers have to be written, but one
of the dangers of doing so is that people will start to
base semantic discussions on the (current) implementation.
The rule "prefer static forms" is good because it should be
true for all implementations of AspectJ. The optimization for
this(Type) will not be, and the practice of decompiling
code to understand or demonstrate semantics should be avoided.
I understand that you were proving that this(Type) has been
optimized (in which cases?), but users might start trying
to prove things using decompilers, and then we'll be talking
in bytecode. Not yummy!
> ------------Original Message------------
> From: "Ron Bodkin" <rbodkin@xxxxxxxxxxxxxx>
> To: aspectj-users@xxxxxxxxxxx
> Date: Sat, Jul-17-2004 8:45 AM
> Subject: RE: [aspectj-users] [newbie] General help needed here.....
>
> Yes Wes, it is true that using the declaring type in the signature is
> useful and can be appropriate for those who have some experience with
> AspectJ. However, for new users it's helpful to get in the mindset of
> using this to specify types instead of doing it in the method signature,
> instead of trying to remember that using declaring types with call is
> problematic and using them with execution is ok (remember that Jerry
> started off using call with a static type in the signature!) And it is also
> a good rule because it's binding the currently executing object in your
> pointcut is commonly done.
>
> By the way, this(Type) && execution(...) has *no* dynamic test (+), and
> with the AspectJ 1.2 compiler optimizations should be compiled about
> equally quickly (e.g., slide 96 from Andy Clement's data at
> http://newaspects.com/presentations/Enterprise%20AOP%20AOSD%202004.ppt which shows
> some related improvements, although not the performance of this(..) &&
> execution(..)).
>
> It is true that it's not statically resolvable for declare
> warning/error (although I'd like to see the compiler restriction eased to allow use
> pointcuts for any special cases where no dynamic test would be required
> to resolve a pointcut; maybe some day). And it also isn't useful for
> statics (clearly). But these are specialized scenarios, not the general
> rule.
>
> Re: configuring AspectJ with Struts, the aTrack project is a working
> example that uses Struts with AspectJ.
>
> Ron
>
> (+) See section 4.1.2 in "Advice Weaving in AspectJ"
> http://www.hugunin.net/papers/aosd-2004-cameraReady.pdf. Also I compiled two versions of
> an aspect with AspectJ 1.2 and found identical bytecode:
>
> public aspect ExecBytecode {
> void foo() {}
> before() : this(ExecBytecode) && execution(* foo()) {}
> }
>
> Then from "javap -c ExecBytecode"
>
> foo();
> Code:
> 0: invokestatic #49; //Method aspectOf:()LExecBytecode;
> 3: invokevirtual #51; //Method
> ajc$before$ExecBytecode$1$eb4dac00:()V
> 6: return
>
> public void ajc$before$ExecBytecode$1$eb4dac00();
> Code:
> 0: return
>
> public aspect ExecBytecode {
> void foo() {}
> before() : execution(* ExecBytecode.foo()) {}
> }
>
> Produces:
> void foo();
> Code:
> 0: invokestatic #49; //Method aspectOf:()LExecBytecode;
> 3: invokevirtual #51; //Method
> ajc$before$ExecBytecode$1$b5db75e4:()V
> 6: return
>
> public void ajc$before$ExecBytecode$1$b5db75e4();
> Code:
> 0: return
>
> Ron Bodkin
> Chief Technology Officer
> New Aspects of Software
> o: (415) 824-4690
> m: (415) 509-2895
>
> > ------------Original Message------------
> > From: "Wes Isberg" <wes@xxxxxxxxxxxxxx>
> > To: aspectj-users@xxxxxxxxxxx
> > Date: Fri, Jul-16-2004 11:06 PM
> > Subject: RE: [aspectj-users] [newbie] General help needed here.....
> >
> > Hi Ron (, Jerry) -
> >
> > re:
> > > As a general rule, you probably don't want to use the form of
> > signature
> > > you have in that pointcut (which matches based on static types
> > instead
> > > of runtime instances).
> >
> > I've never heard this rule and I believe it is not correct;
> > The original form
> >
> > execution(ReturnType DeclaringType.methodName(..))
> >
> > is better than
> >
> > execution(ReturnType methodName(..)) && this(DeclaringType)
> >
> > *because* it can be resolved staticly and requires no dynamic test
> > (faster compile, faster implementation, and better IDE support).
> >
> > You might be confusing this situation with the suggestion for
> > the call pointcut not to use the declaring type in the call.
> > This suggestion is because the signature of a call join point
> > refers to the type of the reference (at the call site), not the
> > type of the referent class (at run time). So when people
> > write
> >
> > call(ReturnType DeclaringType.methodName(..))
> >
> > they usually mean
> >
> > call(ReturnType methodName(..)) && target(DeclaringType)
> >
> > (hence the suggestion).
> >
> > Wes
> >
> > P.S. - If someone does figure out how to configure AspectJ
> > with Struts, etc, it would be great to contribute back a
> > description to the mailing list or a bug, for inclusion in
> > the sample code repository...
> >
> >
> > > ------------Original Message------------
> > > From: "Ron Bodkin" <rbodkin@xxxxxxxxxxxxxx>
> > > To: aspectj-users@xxxxxxxxxxx
> > > Date: Fri, Jul-16-2004 4:09 PM
> > > Subject: RE: [aspectj-users] [newbie] General help needed here.....
> > >
> > > Jerry,
> > >
> > > A couple of things to try:
> > > 1) Make sure that you are opening the affected file with the
> AspectJ
> > > editor and not the Java editor. You should go into window |
> > preferences |
> > > file associations and make sure that AspectJ is set the the default
>
> > for
> > > .java files
> > > 2) Try adding this line, to see if the pointcut is matching:
> > >
> > > declare warning: actionCall() : "in action execution";
> > >
> > > As a general rule, you probably don't want to use the form of
> > signature
> > > you have in that pointcut (which matches based on static types
> > instead
> > > of runtime instances). It should work for executions, but a better
> > > version is:
> > >
> > > pointcut actionExecute() : execution(public ActionForward
> > > execute(ActionMapping, ActionForm,
> > > HttpServletRequest, HttpServletResponse))) && this(Logon_Action);
> > >
> > > Ron
> > >
> > > p.s. there's an already defined, debugged version of a pointcut for
>
> > > struts action execution in the aTrack project: see
> > > ajee.component.StrutsPointcuts. aTrack is at
> > https://atrack.dev.java.net/
> > >
> > > public pointcut actionExecute(Action action, ActionMapping
> > mapping,
> > > ActionForm form,
> > > HttpServletRequest request, HttpServletResponse response) :
> > > execution(ActionForward Action.execute(ActionMapping,
> > > ActionForm,
> > > HttpServletRequest, HttpServletResponse)) &&
> this(action)
> >
> > > &&
> > > args(mapping, form, request, response);
> > >
> > >
> > > Ron Bodkin
> > > Chief Technology Officer
> > > New Aspects of Software
> > > o: (415) 824-4690
> > > m: (415) 509-2895
> > >
> > > > ------------Original Message------------
> > > > From: "Jerry Jalenak" <Jerry.Jalenak@xxxxxxxxxx>
> > > > To: "'aspectj-users@xxxxxxxxxxx'" <aspectj-users@xxxxxxxxxxx>
> > > > Date: Fri, Jul-16-2004 1:07 PM
> > > > Subject: RE: [aspectj-users] [newbie] General help needed
> here.....
> > > >
> > > > Another possibility that just occurred to me....
> > > >
> > > > Since Logon_Action extends Action, do I need to 'expose' the
> > > > org.apache.struts.action.Action class to the aspect?
> > > >
> > > > Jerry Jalenak
> > > > Development Manager, Web Publishing
> > > > LabOne, Inc.
> > > > 10101 Renner Blvd.
> > > > Lenexa, KS 66219
> > > > (913) 577-1496
> > > >
> > > > jerry.jalenak@xxxxxxxxxx
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Ramnivas Laddad [mailto:ramnivas@xxxxxxxxxxxxxxx]
> > > > > Sent: Friday, July 16, 2004 2:29 PM
> > > > > To: aspectj-users@xxxxxxxxxxx
> > > > > Subject: Re: [aspectj-users] [newbie] General help needed
> > here.....
> > > > >
> > > > >
> > > > > Hi Jerry,
> > > > >
> > > > > Otávio's suggestion of using execution() PCD is the right one.
> > > > >
> > > > > It is okay to use any number of aspects crosscutting a class.
> > > > > Just a guess: Do you have every referred type in the pointcut
> > > > > definition (in your case ActionMapping, ActionForm,
> > > > > HttpServletRequest, HttpServletResponse) appropriately
> imported.
> > > > >
> > > > > -Ramnivas
> > > > >
> > > > > ===
> > > > >
> > > > > Ramnivas Laddad,
> > > > > Author, AspectJ in Action
> > > > > http://ramnivas.com
> > > > >
> > > > > Jerry Jalenak wrote:
> > > > >
> > > > > >Otavio,
> > > > > >
> > > > > >Thanks for the reply. Change the PCD from call to execution
> > > > > didn't seem to
> > > > > >change anything. However, I starting to think I have
> > > > > something else wrong.
> > > > > >In the AspectJ Visualizer perspective, I am only seeing
> > > > > where one aspect has
> > > > > >been applied (I have two). Is it not possible to have more
> > > > > than one aspect
> > > > > >class?
> > > > > >
> > > > > >Thanks....
> > > > > >
> > > > > >Jerry Jalenak
> > > > > >Development Manager, Web Publishing
> > > > > >LabOne, Inc.
> > > > > >10101 Renner Blvd.
> > > > > >Lenexa, KS 66219
> > > > > >(913) 577-1496
> > > > > >
> > > > > >jerry.jalenak@xxxxxxxxxx
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >>-----Original Message-----
> > > > > >>From: Otávio Augusto Lazzarini Lemos
> [mailto:oall@xxxxxxxxxxx]
> > > > > >>Sent: Friday, July 16, 2004 1:31 PM
> > > > > >>To: aspectj-users@xxxxxxxxxxx
> > > > > >>Subject: Re: [aspectj-users] [newbie] General help needed
> > > here.....
> > > > > >>
> > > > > >>
> > > > > >>You should use an execution PCD. In your example the calls to
> > > > > >>Logon_action.execute(ActionMapping, ActionForm,
> > > HttpServletRequest,
> > > > > >>
> > > > > >>
> > > > > >>>HttpServletResponse) are the intercepted join points, and
> > > > > >>>
> > > > > >>>
> > > > > >>not the actual
> > > > > >>execution of the method (try to look at the places where you
> > > > > >>call the method).
> > > > > >>Tell me if it works with the execution instead of the call
> PCD.
> > > > > >>
> > > > > >>Otávio
> > > > > >>
> > > > > >>Citando Jerry Jalenak <Jerry.Jalenak@xxxxxxxxxx>:
> > > > > >>
> > > > > >>
> > > > > >>
> > > > > >>>First, thanks to Rod, Adrian, and Ramnivas for their help
> > > > > >>>
> > > > > >>>
> > > > > >>the other day. I
> > > > > >>
> > > > > >>
> > > > > >>>think I'm starting to get the hang of this....
> > > > > >>>
> > > > > >>>That being said, I'm stuck as to why the following doesn't
> > > > > >>>
> > > > > >>>
> > > > > >>work. I've just
> > > > > >>
> > > > > >>
> > > > > >>>upgraded to the AJDT 1.1.11 plug-in, if it matters.
> > > > > >>>
> > > > > >>>Here's the aspect :
> > > > > >>>
> > > > > >>> public aspect MemberSolutions_BaseActionAspect
> > > > > >>> {
> > > > > >>> // ~ Pointcut definitions
> > > > > >>>
> > > > > >>> pointcut actionCall() :
> > > > > >>> (call(public ActionForward
> > > > > >>>Logon_Action.execute(ActionMapping, ActionForm,
> > > > HttpServletRequest,
> > > > > >>>HttpServletResponse)));
> > > > > >>>
> > > > > >>> // ~ Advice definitions
> > > > > >>>
> > > > > >>> before() : actionCall()
> > > > > >>> {
> > > > > >>> System.out.println("here i am");
> > > > > >>> }
> > > > > >>> }
> > > > > >>>
> > > > > >>>and the class I'm trying to weave it into :
> > > > > >>>
> > > > > >>> public class Logon_Action extends Action
> > > > > >>> {
> > > > > >>> public ActionForward execute(ActionMapping
> > _actionMapping,
> > > > > >>> ActionForm _actionForm, HttpServletRequest
> > > _request,
> > > > > >>> HttpServletResponse _response)
> > > > > >>> {
> > > > > >>> Logon_ActionForm form = (Logon_ActionForm)
> > _actionForm;
> > > > > >>> return null;
> > > > > >>> }
> > > > > >>> }
> > > > > >>>
> > > > > >>>Everything compiles OK (no errors, anyway), but when I
> > > > > >>>
> > > > > >>>
> > > > > >>check the class I
> > > > > >>
> > > > > >>
> > > > > >>>don't see any indication that the aspect is being applied.
> > > > > >>>
> > > > > >>>
> > > > > >>I expect to see
> > > > > >>
> > > > > >>
> > > > > >>>an indicator on the first statement of the class....
> > > > > >>>
> > > > > >>>I'm probably being dense on this, and it's something really
> > > > > >>>
> > > > > >>>
> > > > > >>stupid, but I
> > > > > >>
> > > > > >>
> > > > > >>>can't seem to figure it out. Any help?
> > > > > >>>
> > > > > >>>Thanks guys!
> > > > > >>>
> > > > > >>>Jerry Jalenak
> > > > > >>>Development Manager, Web Publishing
> > > > > >>>LabOne, Inc.
> > > > > >>>10101 Renner Blvd.
> > > > > >>>Lenexa, KS 66219
> > > > > >>>(913) 577-1496
> > > > > >>>
> > > > > >>>jerry.jalenak@xxxxxxxxxx
> > > > > >>>
> > > > > >>>
> > > > > >>>This transmission (and any information attached to it) may
> > > > > >>>
> > > > > >>>
> > > > > >>be confidential
> > > > > >>
> > > > > >>
> > > > > >>>and
> > > > > >>>is intended solely for the use of the individual or entity
> > > > > >>>
> > > > > >>>
> > > > > >>to which it is
> > > > > >>
> > > > > >>
> > > > > >>>addressed. If you are not the intended recipient or the
> > > > > >>>
> > > > > >>>
> > > > > >>person responsible
> > > > > >>
> > > > > >>
> > > > > >>>for
> > > > > >>>delivering the transmission to the intended recipient, be
> > > > > >>>
> > > > > >>>
> > > > > >>advised that you
> > > > > >>
> > > > > >>
> > > > > >>>have received this transmission in error and that any use,
> > > > > >>>
> > > > > >>>
> > > > > >>dissemination,
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> > > > > >>
> > > > > >>>forwarding, printing, or copying of this information is
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> > > > > >>>If you have received this transmission in error, please
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> > > > > >>
> > > > > >>>LabOne at the following email address:
> > > > > >>>
> > > > > >>>
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> > > > > >>
> > > > > >>
> > > > > >>>_______________________________________________
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