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Re: [aspectj-users] Signature represents top-level class
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Hi all -
Just to add: the programming guide, semantics appendix has
a section describing the signature for each join point, for
those who want to know about other join points besides
method-execution.
Wes
P.S. And for the truly language-obsessed, I was surprised to realize
(in another thread on this list) that the JLS never says methods
are "defined"; they are "declared", so the programming guide says,
At a method execution join point, the signature a method signature
whose qualifying type is the declaring type of the method.
Note one side-effect of this and our implementation of inter-type
method declarations on interfaces: the declaring type from the
join point signature will never show up as the interface itself,
except when the method is declared on an interface in an aspect.
Programmers (like me) who think of the interface as "declaring"
the method and the implementing classes as "defining" the method
might be confused by this.
> ------------Original Message------------
> From: Matthew Webster <matthew_webster@xxxxxxxxxx>
> To: aspectj-users@xxxxxxxxxxx
> Date: Mon, Sep-27-2004 2:05 AM
> Subject: Re: [aspectj-users] Signature represents top-level class
>
>
>
>
>
> Sarah,
>
> As Ramnivas points out the Signature describes the defining type of the
> currently executing join point. This becomes important when overriding
> methods:
>
> package com.sarah;
>
> public class MyImpl extends MyParent {
>
> public void someMethod() {
> }
>
> public void invoke() {
> super.invoke();
> }
> public static void main(String[] args) {
> new MyImpl().invoke();
> }
> }
>
> package com.sarah;
>
> public aspect MyAspect {
> pointcut MyImpl(com.sarah.MyImpl impl)
> : execution(* *(..)) && this(impl);
>
> before(com.sarah.MyImpl impl) : MyImpl(impl) {
> System.out.println(thisJoinPoint.getSignature().toLongString()
> + "
> " + impl);
> }
> }
>
> Running this modified version of your example gives:
>
> public void com.sarah.MyImpl.invoke() com.sarah.MyImpl@187aeca
> public void com.sarah.MyParent.invoke() com.sarah.MyImpl@187aeca
>
> This is why it is important to trace both static (Signtaure) and
> dynamic
> (this) information so that you know where you are and who you are.
>
> Matthew Webster
> AOSD Project
> Java Technology Centre, MP146
> IBM Hursley Park, Winchester, SO21 2JN, England
> Telephone: +44 196 2816139 (external) 246139 (internal)
> Email: Matthew Webster/UK/IBM @ IBMGB, matthew_webster@xxxxxxxxxx
> http://w3.hursley.ibm.com/~websterm/
>
>
> Ramnivas Laddad <ramnivas@xxxxxxxxxxxxxxx>@eclipse.org on 25/09/2004
> 00:40:55
>
> Please respond to aspectj-users@xxxxxxxxxxx
>
> Sent by: aspectj-users-admin@xxxxxxxxxxx
>
>
> To: aspectj-users@xxxxxxxxxxx
> cc:
> Subject: Re: [aspectj-users] Signature represents top-level class
>
>
> Sarah,
>
> Since the invoke method is defined in MyParent, the signature (which is
> anchored to the join point) prints MyParent.
>
> If you want to print the exact type of the object on which the method
> is
> invoked you could capture the 'this' object as context and print its
> class name. Here are two possible implementations:
>
> public aspect MyAspect {
> pointcut MyImpl(Object theThis)
> : execution(* *(..)) && this(com.sarah.MyImpl) &&
> this(theThis);
>
> before() : MyImpl() {
>
> System.out.println(thisJoinPoint.getSignature().toLongString());
> System.out.println(theThis.getClass());
> }
> }
>
>
> Or
>
> public aspect MyAspect {
> pointcut MyImpl()
> : execution(* *(..)) && this(com.sarah.MyImpl);
>
> before() : MyImpl() {
>
> System.out.println(thisJoinPoint.getSignature().toLongString());
> System.out.println(thisJoinPoint.getThis().getClass());
> }
> }
>
>
> -Ramnivas
>
> ===
> Ramnivas Laddad,
> Author, AspectJ in Action
> http://ramnivas.com
>
>
>
> Sarah Haskins wrote:
>
> >I was hoping someone might be able to explain a) why when I call
> thisJoinPoint.getSignature().toLongString() I get the full method
> signature
> for the top-level parent and b) how I might instead obtain the
> signature of
> the actual instance on which the pointcut matched.
> >
> >Let me provide some code in case I'm not being clear.
> >
> >I have an Aspect like such...
> >
> >public aspect MyAspect {
> > pointcut MyImpl()
> > : execution(* *(..)) && this(com.sarah.MyImpl);
> >
> > before() : MyImpl() {
> >
> System.out.println(thisJoinPoint.getSignature().toLongString());
> > }
> >}
> >
> >And I have a top-level parent class like...
> >
> >public abstract class MyParent {
> > public abstract void someMethod();
> > public void invoke() {
> > ... do some simple stuff...
> > }
> >}
> >
> >And I have an implementation of the abstract class like...
> >
> >public class MyImpl extends MyParent {
> > public void someMethod() {
> > // whatever
> > }
> >}
> >
> >When I run this code and call myImpl.invoke(), the Aspect prints
> out...
> > public void com.sarah.MyParent.invoke()
> >
> >Ideally I'd like to get public void com.sarah.MyImpl.invoke() instead.
> >
> >Apologies if this is common knowledge, but I can't seem to find
> information on this anywhere. (BTW, I'm subscribed to this email list,
> but
> I get rejected when I try to search old emails from the website.
> Anyone
> know about that too?)
> >
> >Thanks all!
> >
> >------------------------------
> >Sarah Haskins
> >Software Development
> >sarah.haskins@xxxxxxxx
> >Sakonnet Technology
> >594 Broadway, Suite 1008
> >New York NY 10012
> >www.sknt.com
> >+1 917 237 38__ direct
> >+1 212 343 3103 fax
> >
> >
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