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Re: [aspectj-users] advice precedence
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> Any insight for the use case of supporting that ?
See my previous post in reply to Pope's message for that.
> From the rule you explain, it seems that actually the behavior is half
> way that since "after" is having a special rule that means that we can
> actually *never* have "after -> around".
> So why "before" is not having a special rule as well ?
This isn't correct. If I have ordered source declarations (around, after),
then according to rule 2, since "either" of the declarations is after
advice, the precedence is:
after -> around
and you would see:
...
hello
around-exit
after
With ordered source declarations (after, around), the precedence is:
around -> after
and you would see:
...
hello
after
around-exit
Regards, Adrian.
-- Adrian
Adrian_Colyer@xxxxxxxxxx
Alexandre Vasseur <avasseur@xxxxxxxxx>
Sent by: aspectj-users-admin@xxxxxxxxxxx
04/01/2005 13:43
Please respond to
aspectj-users@xxxxxxxxxxx
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cc
Subject
Re: [aspectj-users] advice precedence
Thanks for the explanation.
Any insight for the use case of supporting that ?
If I am right, I think the others that supports "before" (AspectWerkz,
Spring AOP) are assuming that ALL "before" (even between different
aspects no matter precedence of those) are all before the "around",
etc
ie that advice kind precedence wins over user defined precedence.
This allow to not have advice precedence circularity (only aspect
precedence circularity).
From the rule you explain, it seems that actually the behavior is half
way that since "after" is having a special rule that means that we can
actually *never* have "after -> around".
So why "before" is not having a special rule as well ?
How many of you are using this source code driven precedence ?
I am suprised since I just discovered that when commenting /
uncommenting some code in my aspects.
Further on, discussing with friends that had read both books (Manning
and Wiley) it appeared that this fact was not clear to them neither.
Ramnivas any comments ?
Alex
On Tue, 4 Jan 2005 13:18:03 +0000, Adrian Colyer
<adrian_colyer@xxxxxxxxxx> wrote:
> A good question to start the new year with :)
>
> > What is the rule for precedence between lets say a before, around and
> > an after advice defined in one single aspect and affecting the same
> > joinpoint ?
>
> > But when trying some with AJDT / AJ 1.2.0 on Eclipse 3.0.1 I have some
> > results that depends on the source code order of my advices:
>
> As you quote from the user guide:
>
> > "If the two pieces of advice are defined in the same aspect, then
> > there are two cases:
> > * If either are after advice, then the one that appears later in
> > the aspect has precedence over the one that appears earlier.
> > * Otherwise, then the one that appears earlier in the aspect has
> > precedence over the one that appears later. "
>
> On the "way in" to a join point, the advice with the highest precedence
> executes first, and on the "way out" the advice with the highest
> precedence executes last.
>
> Here "later in the aspect" means "later in the source file" - ie.
exactly
> that the order depends on the order of the advice declarations in the
> source file.
>
> > "before, around, after" in source leads to
> > before
> > around -->
> > hello
> > around --<
> > after
>
> This order is derived as follows:
>
> given the pair (before, around) then by the second clause the one that
> appears earlier in the source has precedence:
>
> before -> around
>
> given the pair(around, after) the by the first clause the after advice
has
> precedence so we get:
>
> after -> around
>
> on the "way in" the highest precedence goes first so we see "before,
> around-entry" and on the way out the highest precedence goes last so we
> see "around-exit, after". Giving:
>
> before
> around-entry
> hello
> around-exit
> after
>
> > "around, before, after" in source leads to
> > around -->
> > before
> > hello
> > around --<
> > after
>
> This order is derived as follows:
>
> given the pair (around, before) then by the second clause the one that
> appears earlier in the source has precedence:
>
> around -> before
>
> given the pair (around, after) then by the first clause the after advice
> has precedence:
>
> after -> around
>
> on the "way in" this gives us "around-entry, before" and on the
"way-out"
> this gives us "around-exit, after". Giving:
>
> around-entry
> before
> hello
> around-exit
> after
>
> > "before, after, around" in source leads to a compilation error that
> > says "can't determine precedence between two or more pieces of advice
> > that apply to the same join point: method-execution(void
> > preced.Preced.hello())"
>
> Applying the first rule to the pair (before, after) we see that the
after
> advice has precedence:
>
> after -> before
>
> Applying the first rule to the pair (after, around) we see that the
around
> advice has precedence:
>
> around -> after
>
> Applying the second rule to the pair (before, around), we see that the
> before advice has precedence:
>
> before -> around
>
> If we put these together we get: around -> after -> before -> around ->
> ...
> In previous versions of AspectJ I recall this being reported as a
> "circular precedence error" or some similar wording - but the error
> message has subsequently been improved to give the one that you
witnessed.
>
> -- Adrian
> Adrian_Colyer@xxxxxxxxxx
>
> Alexandre Vasseur <avasseur@xxxxxxxxx>
> Sent by: aspectj-users-admin@xxxxxxxxxxx
> 03/01/2005 10:17
> Please respond to
> aspectj-users@xxxxxxxxxxx
>
> To
> aspectj-users@xxxxxxxxxxx
> cc
>
> Subject
> [aspectj-users] advice precedence
>
>
> Hi
>
> I discovered today that one of my assumption seems to be wrong.
> What is the rule for precedence between lets say a before, around and
> an after advice defined in one single aspect and affecting the same
> joinpoint ?
>
> In both Manning and Wiley books on AspectJ, I understood that it would
> happen like this:
> "before, around, after".
>
> But when trying some with AJDT / AJ 1.2.0 on Eclipse 3.0.1 I have some
> results that depends on the source code order of my advices:
>
> "before, around, after" in source leads to
> before
> around -->
> hello
> around --<
> after
>
> "around, before, after" in source leads to [ see the before nested
> within the around' proceed() ]
> around -->
> before
> hello
> around --<
> after
>
> "before, after, around" in source leads to a compilation error that
> says "can't determine precedence between two or more pieces of advice
> that apply to the same join point: method-execution(void
> preced.Preced.hello())"
>
> Reading the AspectJ Programming guide did not give me a clue except
> perhaps:
> "If the two pieces of advice are defined in the same aspect, then
> there are two cases:
> * If either are after advice, then the one that appears later in
> the aspect has precedence over the one that appears earlier.
> * Otherwise, then the one that appears earlier in the aspect has
> precedence over the one that appears later. "
>
> Does that means that there is no implicit rule that say that a before
> advice will execute before the around advice (as long as those are in
> the same aspect).
> Why the 3rd source order leads to a compilation error ?
>
> Below the little code snip
> Alex
>
> package preced;
> public class Preced {
>
> public void hello() {
> System.out.println(" hello");
> }
>
> public static void main(String[] args) {
> (new Preced()).hello();
> }
>
> static aspect MyAspect {
> before() : execution(* *Preced.hello())
{
> System.out.println("before");
> }
> Object around() : execution(*
> *Preced.hello()) {
> System.out.println("around -->");
> proceed();
> System.out.println("around --<");
> return null;
> }
> after() : execution(* *Preced.hello())
{
> System.out.println("after");
> }
> }
> }
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