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RE: [aspectj-users] Question re: declare error

Hi Peter: the topic of getting old values of a field during set has come up before on the mailing list and as youâve determined the only way to do it where you advise different fields is via reflection (e.g., see Matthew Websterâs post at http://dev.eclipse.org/mhonarc/lists/aspectj-users/msg04126.html). ÂI see how the obfuscator might break with reflective code (though Iâd hope that an obfuscator wouldnât: lots of libraries now rely on reflection). One idea might be to track the old value of the field also in advice so you can compare the previous value to the current value (e.g., using your map that associates static parts with state).

 

Hope that helps,

Ron

 


From: aspectj-users-bounces@xxxxxxxxxxx [mailto:aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Peter Murray
Sent: Thursday, September 14, 2006 1:23 PM
To: aspectj-users@xxxxxxxxxxx
Subject: Re: [aspectj-users] Question re: declare error

 

Ron,

Thanks a bunch!  That does the trick.  I was suspicious that there might be an operator for "subtypes".

Now, the real question is - how can I get ahold of the original value of a field during around set advice so I can use AspectJ to create the ValueChange objects and post them based on the @Transactional annotation.  It seems the only way is through reflection which will break once we obfuscate...

Any thoughts on that?

Cheers,

pete
peter m. murray
pete@xxxxxxxxxxxx

On 9/14/06, Ron Bodkin <rbodkin@xxxxxxxxxxxxxx> wrote:

Hi Peter,

 

I would use within(Change+) instead of this(Change). That isn't the exact same semantics as using this (*) but in most cases it would capture your intent: it makes it an error to set the field outside of code that's in a subtype of Change.

 

(*) it's based on the join points being lexically located inside Change. So it can differ because it won't allow setting the fields in a base class that might be extended by a type that extends Change. It also doesn't allow for setting inside of inter-type declared methods (you could extend the rule to allow those if that matters to you).

 


From: aspectj-users-bounces@xxxxxxxxxxx [mailto: aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Peter Murray
Sent: Thursday, September 14, 2006 10:41 AM

Subject: Re: [aspectj-users] Question re: declare error

 

Thanks for your reply, Elizabeth.

That makes sense - do you see a way to accomplish what I am trying to do?

Cheers,

pete
peter m. murray
pete@xxxxxxxxxxxx

On 9/14/06, Echlin Harmer, Elizabeth <echline@xxxxxxx> wrote:

Peter

As I understand it, declare is a compile time error or warning; this(), target() and args() are all run time checks. Except in the simplest of cases, it is not possible to tell at compile time what the type of this, target or args will be.

Elizabeth

-----Original Message-----
From: aspectj-users-bounces@xxxxxxxxxxx [mailto:aspectj-users-bounces@xxxxxxxxxxx]On Behalf Of Peter Murray
Sent: September 14, 2006 1:12 PM
To: aspectj-users@xxxxxxxxxxx
Subject: [aspectj-users] Question re: declare error


I'd like to declare an error if my @Transactional attributed instance variables are being set outside of the context of a Change object.  In other words, I'd like to have an error in this case:

public class Foo
{
    @Transactional
     String name

      public void setName(String newName)
      {
            name = newName;
      }
}

But not in this case:

public class Foo
{
    @Transactional
     String name

      public void setName(String newName)
      {
            new ValueChange<String>(name, newName)
            {
                 public void set(String value)
                  {
                        name = value;
                  }
             }.post();
      }
}

It seems like this kind of aspect should do that:

public aspect FieldChangeAspect
{
    declare error :
        set(@Transactional * *) &&
        !this(Change)  : "Set of @Transactional variable not in Change object";
}

But this gives me an error saying "this() pointcut designator cannot be used in declare statements."  BTW,  target(), and args() also give the same error for declare statements i guess, so you can't filter on types of this, target, or args in declares.

Am I missing something?  Is there a reason for this or could these be enhancements?

Cheers,
--
-pete
peter m. murray
pete@xxxxxxxxxxxx




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--
-pete
peter m. murray
pete@xxxxxxxxxxxx


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--
-pete
peter m. murray
pete@xxxxxxxxxxxx