Re: [aspectj-users] Signature represents top-level class

[Matthew Webster <matthew_webster@xxxxxxxxxx>]

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
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