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RE: [aspectj-users] Parameters 
Wes,

In thinking about the problem more fully, I see (in my humble opinion) a
limitation (severe if you consider legacy systems) in the way aspectj
handles the arguments to methods in defining PCD.  If you look at the way it
works today, aspectj requires that if you have a need to pull out on certain
parameters to a given method, you must define (and must continue to require)
the order in which they are defined in order to expose them to the advice.

To give you an idea of where I am using this is that I want to pull out all
the common argument/parameter validation rules that current have scattered
all over the place in our code base with one central validation service via
aspectj.  If I am required to re-order the arguments/parameters to these
methods I may end up touching somewhere around 300 to 400 classes.  On the
flip side if I could pick-out the arguments any where they exist I would
only have to affect 62 classes or the ones that have the rules in them.

Please let me know if I am wrong of off base with this assessment.

Thanks,

Ron DiFrango


-----Original Message-----
From: DiFrango, Ron 
Sent: Wednesday, August 20, 2003 8:47 AM
To: 'aspectj-users@xxxxxxxxxxx'
Subject: RE: [aspectj-users] Parameters


Wes,

Thanks for your answer and it does not work in 1.0 as that is the version I
am on currently.  Actually it was what I expected.  I am surprised that I am
one of the first to bring this up.

I personally would like to see the ability to use multiple wildcards in a
PCD.  The main driver for me is that I am retrofitting old code and I would
prefer to keep the pre-existing interfaces as much intact as possible.

Should I submit a bug report on this?

Thanks,

Ron DiFrango


-----Original Message-----
From: Wes Isberg [mailto:wes@xxxxxxxxxxxxxx] 
Sent: Wednesday, August 20, 2003 12:03 AM
To: aspectj-users@xxxxxxxxxxx
Subject: Re: [aspectj-users] Parameters


   args(.., ClassX, ..)

should have worked in AspectJ 1.0, but, as Erik noted for 1.1,

   We did not implement the handling of more than one ..
   wildcard in args PCDs (rarely encountered in the wild)
   because we didn't have the time. This might be available
   in later releases if there is significant outcry
 
http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/aspectj-home/doc/REA
DME-11.html#language

I'm not sure if a bug would qualify as a significant outcry, but it would be
a place others could chime in.

(Also, it's a doc bug that ".." in args(...) is not better documented. I
couldn't find it in either quick reference or the programming guide
semantics appendix; perhaps my search was bad.)

A workaround for now is to test the args directly, perhaps even in an if
pointcut:

aspect A {
    private static boolean hasArg(Class c, Object[] args) {
         for (int i = 0; i < args.length; i++) {
            if ((null != args[i]) &&
               c.isAssignableFrom(args[i].getClass())) {
               return true;
            }
         }
         return false;
    }
    before() : ... && if(hasArg(ClassX.class, thisJoinPoint.getArgs()) {
        ...
    }
}

Obviously, that won't pick out a null ClassX arg, and it
can be expensive, depending on the rest of your pointcut.

Wes


DiFrango, Ron wrote:

> All,
> 
> I could not find an answer to this in any of the old postings.  I have
> methods that take a common parameter.  The problem is that depending 
> on the method call this parameter may be listed anywhere in the method 
> signature. So for example:
> 
> 	public class ParametersInMethodCalls
> 	{
> 		public void example1(ClassX x, double I, String s)
> 		{
> 		}
> 
> 		public void example2(int I, ClassX x, double d)
> 		{
> 		}
> 
> 		public void example2(float I, String s, ClassX x)
> 		{
> 		}
> 	}
> 
> My question is can I define a pointcuts that picks out all the above
> combinations without having to "code if you will" the different 
> permutations possible?  I have tried the following 
> examples/permutations:
> 
> 	pointcut examples(ClassX x) : 
> 		execution(public * ParametersInMethodCalls.*(..))
> 		&& args(.., x);
> 
> 	==> Afected example2
> 
> 	pointcut examples(ClassX x) : 
> 		execution(public * ParametersInMethodCalls.*(..))
> 		&& args(x, ..);
> 
> 	==> Afected example1
> 
> 	pointcut examples(ClassX x) : 
> 		execution(public * ParametersInMethodCalls.*(..))
> 		&& args(*, x);
> 
> 	==> Affect nothing
> 
> The important thing to note is that all the methods I want to pick out
> have the common input of ClassX, but there is an indeterminate number 
> of other parameters to these methods.  Furthermore, I would prefer to 
> avoid having to change the underlying code as it affects a large body 
> of code.
> 
> Thanks in advance,
> 
> Ron DiFrango
>  
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