Re: [aspectj-dev] Adding a field to a direct subclass only...

[Alex Villazon <alex.villazon@xxxxxxxxxxx>]

On Aug 8, 2008, at 5:05 PM, Eric Bodden wrote:

> Hi Alex.
>
> I don't think that AspectJ can allow for that because AspectJ respects
> Java's rules for subtyping and inheritance.
>
> I cannot think of a single reason for why it would make sense to have
> fields on a direct subclass only. Usually this indicates that the
> class hierarchy that you are crosscutting is briken in the first
> place.

 Hi Eric,
     The use of IDT helps me to enable a counter associated to each  
object (to avoid using perthis/pertarget because of performance issues  
and because I cannot add that field on java.lang.Object in Sun VM.. J9  
accepts such a modification).

     I want to add the field only on direct subclasses of  
java.lang.Object to avoid the problem of having instance field in  
subclasses that 'hiddes' the value defined in the super class...    
This can be problematic if a variable refers to different subclasses,  
and therefore update the wrong counter...  , i.e. my counter is not  
dependent of the type, but simply per object...

   I had such a problem if the field is added in all direct and  
indirect subclasses..

Cheers,

Alex


> Eric
>
> 2008/8/8 Alex Villazon <alex.villazon@xxxxxxxxxxx>:
> > Hi,
> > I'm trying to use ITD to add a field only to a direct subclass of a  
> > give
> > class (and not to direct and indirect as aspectj allows by  
> > default), but I
> > cannot find the correct expression to do so. The problem is that I  
> > have to
> > keep a single value for every instance (ideally I would like to add  
> > a field
> > to java.lang.Object, but this not possible on Sun's JVM), and if  
> > apply the
> > aspect to "* && !java.lang.Object" the field is added on every  
> > class..
> >
> > I want to do something like:
> >
> > interface MyInterface {}
> > aspect X {
> >    int MyInterface.afield;
> >    declare parents: * && isDirectSubclassOf(java.lang.Object) &&
> > !java.lang.Object implements MyInterface;
> >    ..
> > }
> >
> > Is there a way to specify that?
> >
> > (I cannot use perthis()/pertarget() because it introduces too much
> > overhead..).
> >
> > Many thanks,
> >
> > Alex
> >
> > PS: Is there a way to enable ITD to JDK classes? I was able to  
> > weave aspects
> > that do not use static crosscutting to JDK classes with ajc, but  
> > static
> > crosscutting does not apply to JDK classes. Probably an option  
> > should be
> > added to allow this...
> > _______________________________________________
> > aspectj-dev mailing list
> > aspectj-dev@xxxxxxxxxxx
> > https://dev.eclipse.org/mailman/listinfo/aspectj-dev
>
>
>
> --
> Eric Bodden
> Sable Research Group
> McGill University, Montréal, Canada
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