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Re: [aspectj-users] Guidaance on Cflow usage
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Hi -
Donal Lafferty wrote:
2. With respect to Wes Isberg's comments, I think that I'm working off
the wrong documents. Specifically, the docs I was looking at did not
mention advice execution join points. Perhaps I could take this
opportunity to request the future documentation include the relevant
AspectJ version in their title?
Good point. We'll include the version in the docs.
3. There seems to be a bug with V1.1 in that the 'call' primitive
pointcut designator can be made to select advice execution join points.
> As pointed out earlier 'call ( * *.*())' will match advice execution
> join points, which is not in synch with the Programming Guide
> description of the 'call' designator.
Sounds like a bug! Please do submit, with a test case if possible.
(It's not a bug if it matches calls from the body of advice.)
Wes
-----Original Message-----
From: aspectj-users-admin@xxxxxxxxxxx
[mailto:aspectj-users-admin@xxxxxxxxxxx] On Behalf Of Gregor Kiczales
Sent: 18 August 2003 05:52
To: aspectj-users@xxxxxxxxxxx
Subject: RE: [aspectj-users] Guidaance on Cflow usage
Ramnivas has already pointed out the !within(<aspect>) idiom you want to
use here.
I want to use Donal's message to bring up a couple of points that may be
more
generally helpful. His message raises some issues that I've heard
several
times now, so it seemed worth trying to write down some of the answer.
(Apologies to Donal for dumping all this in response to your message.
Since you're a teacher and a textbook developer I hope you'll forgive
me using your message to stress a general set of points!)
The two key points I want to make are that:
- Join points, pointcuts and advice are orthogonal.
- Advice are on pointcuts, and pointcuts match join points.
So an advice "knows" what pointcut it is on; and poincuts "know"
what join points they match. But there is relationship in the other
direction -- pointcuts don't know what advice is on them; join points
don't know what pointcuts match them, or what advice runs at them.
One consequence of this is that when you are trying to think about why
a particular advice is (or isn't) running, you can focus on the
pointcut,
and what join points it matches. It doesn't matter about what kind of
advice it is.
It can also help sharpen other questions about pointcuts.
For example, in:
Maybe cflow should match all join points during the execution,
even if they are introduced by virtue of the same cflow call.
That description doesn't really fit the AspectJ model. There is no
such thing as a "cflow call". All that is happening is that cflow is
matching a join point, and that join point just happens to arise because
of advice on that pointcut. But the cflow part of the pointcut knows
nothing about the advice.
Similarly, in:
If it is okay for advice statements of an aspect to match pointcuts
in the same aspect, then I shouldn't have to use the mangled name to
do it.
In the AspectJ model, advice statements don't match. Just pointcuts
do. And, as before, the orthogonality of the three concepts makes
how poincuts match join points independent of advice.
Finally, with regard to the details of matching advice execution join
points, the pointcut that does that is 'adviceexecution()'. I can't
remember whether we ever considered trying to have the execution
pointcut
match advice execution join points. adviceexecution came up pretty
late,
so probably not.
-----Original Message-----
From: aspectj-users-admin@xxxxxxxxxxx
[mailto:aspectj-users-admin@xxxxxxxxxxx] On Behalf Of Donal Lafferty
Sent: Sunday, August 17, 2003 1:35 PM
To: aspectj-users@xxxxxxxxxxx
Subject: RE: [aspectj-users] Guidaance on Cflow usage
1. Using cflowbelow does not help. In the example provided, the
pointcut argument of the cflow designator does not explicitly
match the
advice in Cflow.aj. So, using cflowbelow should result in the same
behaviour, and I get the same behaviour when I modify the pointcut to
use cflow instead of cflowbelow.
2. Perhaps the behaviour I'm seeing is not a problem. Maybe cflow
should match all join points during the execution, even if they are
introduced by virtue of the same cflow call. In this light its okay
that calls advice in Cflow.aj are caught.
3. If it is okay for advice statements of an aspect to match
pointcuts
in the same aspect, then I shouldn't have to use the mangled
name to do
it. Should I? If advice statements are legitimate join
points, then I
would expect to be able to use execution designators to pick them out.
In a way I can, ex. call( * *.*( * )) seems to select calls to the
advice in cflow.aj. However, given the claim that aspects
are modelled
on Java types, I would expect that something like call( *
Cflow.*( * ))
would also select advice from the aspect Cflow. Unfortunately it does
not.
DL
-----Original Message-----
From: aspectj-users-admin@xxxxxxxxxxx
[mailto:aspectj-users-admin@xxxxxxxxxxx] On Behalf Of Ramnivas Laddad
Sent: 16 August 2003 20:08
To: aspectj-users@xxxxxxxxxxx
Subject: Re: [aspectj-users] Guidaance on Cflow usage
Donal,
You need to use cflowbelow() pointcut to exclude the join point
itself.
There is a sample chapter (chapter 3) from my book posted that
covers control-flow based pointcuts:
http://www.manning.com/laddad/
-Ramnivas
--- Donal Lafferty <laffertd@xxxxxxxxx> wrote:
Hi!
I'm having trouble coming to grasps with cflow pointcuts. In the
example below, I was surprised to find out that cflow advice is
included
in the set of cflow join points, which leads to an infinite
recursion.
Although I'm tempted to submit this as a bug, I'm not wholly
convinced I
understand what I'm doing. Moreover, the bug submission system is
down.
Any comments on the problem are more than welcome!
Cheers,
DL
WordCounterDemo.java
class WordCounterDemo
{
static String[] smallSample= {"This", "demos", "infinite", "loop",
"in",
"cflow", "before", "advice"};
public static void main(String[] args) {
WordCounter wordCounter = new WordCounter();
String word;
String[] wordList1 = smallSample;
int words = 0;
for (int i = 0; i < wordList1.length; i++) {
word = smallSample[i];
System.out.println("Adding " + word +", as word #" +
(++words));
wordCounter.Add(word);
}
}
}
WordCounter.java
public class WordCounter {
public void Add(String word) {
System.out.println("Add entry, word = "+word.toString());
}
}
Cflow.aj
public aspect Cflow {
pointcut AddCflow(): cflow( execution( * WordCounter.Add( * )));
// In AspectJ 1.0.6 and 1.1 here is an infinite loop here, because
the
// before advice is itself considered a join point in the cflow.
before(): AddCflow() { System.out.println("Before advice
call" ); }
}
CflowWeave.lst
WordCounterDemo.java
WordCounter.java
Cflow.aj
Which compiles with:
ajc -argfile CflowWeave.lst
And runs with:
java -classpatch "%CLASSPATH;./" WordCounterDemo
Gives the output
Adding This, as word#1
Exception in thread "main" java.langStackOverflowError
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