[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [List Home]
Re: [aspectj-users] Re: Access to the aspect in 'pertypewithin' type

So, from the advice you can of course just use 'this' as that will be
the aspect instance.  Your question is more about accessing the
instance from the pointcut rather than the advice as you want to check
a trace guard using if().   If it can be accessed from the if() then
the optimization to lazily build the joinpoint object for passing to
the advice is possible (using what we used to call the lazyTjp
optimization).

Unfortunately you cannot do that right now - traditionally people have
used a single global flag as the primary guard for all tracing across
the system and then within the advice checking on a per type basis.

before(): execution(public * *(..)) && if(isEnabledAnywhere) {
  if (logger.isEnabledFor(getWithinTypeName()) {
    logger.log(thisJoinPoint);
  }
}

This gives you the global control to guard building thisJoinPoint
objects - if tracing is not turned on anywhere, there is no cost for
that.  But if you enable it for any type you will suffer the building
of the tjp object across the system.

It can be optimized and has been mentioned in the past, but I haven't
gotten around to it.  There are a few open bugzilla entries related to
pertypewithin() but I don't think this requirement has been captured
explicitly - feel free to raise an enhancement request for it.

Andy


On 31/01/2008, Andreas Mandel <Andreas.Mandel@xxxxxxxxx> wrote:
> Hello Dean,
>
> thanks for your answer. Actually I already found the documents you
> pointed me to. And pertypewithin works fine with 1.4JDK, at least for
> what I did till now.
>
> My point is not the usage of 'pertypewithin' but the overhead that is
> generated if an condition wants to access the object instance of the
> aspect, related to the current class (DeclaringType).
>
>
> I try it differently:
>
> If a class gets a pertypewithin aspect is gets a private static
> transient <aspect-class> ajc$<package>$ptwAspectInstance; member and a
> method public static <aspect-class> ajc$<package>$localAspectOf() weaved
> in. But accessing these static information is - as far as I found out -
> not directly possible from within a if(..) condition. The only way to
> get the assigned aspect is to call:
> aspectOf(thisJoinPointStaticPart.getSignature().getDeclaringType())
> which is very costly compared to the direct access.
>
>
>
> A sample:
>
> public aspect Tracing pertypewithin(*.*)
> {
>    public boolean mEnabled;
>    public boolean isEnabled ()
>    {
>       return mEnabled;
>    }
>
>    [...]
>
>    before() : !within(Tracing)
> //   && if(mEnabled) not possible, needs static
>       && aspectOf(
>         thisJoinPointStaticPart
>            .getSignature().getDeclaringType()).isEnabled()
>    {
>      [...]
>      ... thisJoinPoint.getArgs() ...
>      [...]
>    }
> }
>
>
> So the question remains: Is this somehow possible today?
>
>
>
> Kind Regards,
>
> Andreas.
>
>
>
>
> Dean Wampler schrieb:
>  > It goes with the aspect declaration:
>  >
>  > public aspect Foo pertypewithin(...mypackage.*) {  // All the types in
>  > "mypackage".
>  > ...
>  > }
>  >
>  > Here's the manual page for it, which is not as easy to get to with a
>  > google search as you would think (aspectj list traffic comes up first...)
>  >
> http://www.eclipse.org/aspectj/doc/released/adk15notebook/pertypewithin.html
>  >
>  > Here's a very long message on the aspectj-dev list that shows an example:
>  > http://dev.eclipse.org/mhonarc/lists/aspectj-dev/msg01259.html
>  >
>  > Also, I couldn't remember if pertypewithin actually works with JDK 1.4,
>  > but apparently it does:
>  > http://dev.eclipse.org/mhonarc/lists/aspectj-users/msg03995.html
>  >
>  > Can you give us some more details about what you're trying to do?
>  >
>  > Hope this helps!
>  > dean
>  >
>  > On Jan 31, 2008, at 2:10 AM, Andreas Mandel wrote:
>  >
>  >> Hello,
>  >>
>  >> I'm quite new to AspectJ so please apologize that some terms might not
>  >> fully hit the target.
>  >>
>  >> I tried hard to find the 'pertypewithin' keyword which allows me to do
>  >> exactly what I wanted. (Guess what - debug logging and tracing). I'm
>  >> working with a 1.4 JDK. Inspecting the generated code there is one thing
>  >> that makes me unhappy because it is not as good as it could be:
>  >>
>  >> To access the DeclaringType's aspect instance in the advice I need to
>  >> call
> aspectOf(thisJoinPointStaticPart.getSignature().getDeclaringType()).
>  >> This generates code that calls the static aspectOf(Class) method of the
>  >> aspect to look up the DeclaringType's aspect instance via
>  >> reflection. This simply returns a pointer back to the member that is
>  >> already statically accessible in the DeclaringType
>  >> (ajc$<...>$ptwAspectInstance).
>  >> This could be directly accessible even in the static arrear (if(...))
>  >> allowing some major improvements - but unfortunately it not exposed to
>  >> the advice.
>  >>
>  >> Am I just missing an other key word to get direct access? Or is this a
>  >> feature that needs to be coded?
>  >>
>  >> If needed I can give more details.
>  >>
>  >>
>  >> Thanks for any feedback,
>  >>
>  >> Andreas.
>  >>
>  >> _______________________________________________
>  >> aspectj-users mailing list
>  >> aspectj-users@xxxxxxxxxxx
>  >> https://dev.eclipse.org/mailman/listinfo/aspectj-users
>  >
>  > Dean Wampler, Ph.D.
>  > dean at objectmentor.com
>  > http://www.objectmentor.com
>  > See also:
>  > http://www.aspectprogramming.com  AOP advocacy site
>  > http://aquarium.rubyforge.org     AOP for Ruby
>  > http://www.contract4j.org         Design by Contract for Java5
>  >
>  >
>  >
>  >
>  > ------------------------------------------------------------------------
>  >
>  > _______________________________________________
>  > aspectj-users mailing list
>  > aspectj-users@xxxxxxxxxxx
>  > https://dev.eclipse.org/mailman/listinfo/aspectj-users
>
> _______________________________________________
> aspectj-users mailing list
> aspectj-users@xxxxxxxxxxx
> https://dev.eclipse.org/mailman/listinfo/aspectj-users
>