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Re: [aspectj-users] Frustrated Newbie

Title: Re: [aspectj-users] Frustrated Newbie
I suggest picking one of your simpler cross-cutting concerns first to see how it goes. Perhaps time-boxing your experiment will keep you from taking too long, should it not work out!

In general, don't forget the important lessons we've learned from pure OOD, especially the value of working with interfaces and annotations, which are another form of abstraction. In particular, when writing aspects and especially pointcuts for these production aspects, try to use only interfaces or annotations that are not likely to change often. A common pitfall in the early days of AOP and AspectJ was to hard-code concrete details of package, class, and method names. As soon as someone refactored one of these names, the aspect broke. Our tools aren't good enough yet to handle these refactorings robustly. (Your example below used interfaces; the point is worth emphasizing, though!)

Of course, this means that the classes you want to advise must implement the interfaces and or have the annotations you need for your pointcuts. Exposing such abstractions is a good idea, anyway!

Good luck and don't hesitate to ask for help on the list as you proceed.

dean

Kevin F wrote:
Thanks.

Actually, I want to use it to implement various mission critical orthogonal crosscuts to dramatically improve project velocity for a deadline in early April.  Do you have experience using AJ for mission critical functionality?  I spent 30+ hours on this problem in the 4 days so I will be able to devote time to fixing problems as long as I can observe the effects of my AJ changes.  How likely is it that I’ll run into any more circumstances where my pointcuts filter far too many joinpoints such as my example below (118 when >3000 should have been found)?  Debugging problems of the nature “the ubiquitous framework chooses not to call my code” are extreme timewasters.    

Kevin


From: Dean Wampler <dean@xxxxxxxxxxxxxxxxxxxxx>
Organization: Aspect Programming
Reply-To: <aspectj-users@xxxxxxxxxxx>
Date: Sun, 25 Feb 2007 10:51:52 -0600
To: <aspectj-users@xxxxxxxxxxx>
Subject: Re: [aspectj-users] Frustrated Newbie

I'm glad you made some headway.  I'm not sure if your original installation process caused problems. I think it should have worked, but I've only used the feature installer myself.

I do believe it's wise to proceed cautiously, since as you've seen, it can take some effort to understand the join point language and other aspects (pardon the pun ;) of AspectJ. I don't know what other aspects you've tried to use, but "policy enforcement" aspects like the one you posted are a good place to start, since they don't implement production functionality, but provide a supporting development role. As you build confidence, you can proceed to more "missing critical" aspects.

Best wishes.

dean

Kevin F wrote:
Re: [aspectj-users] Frustrated Newbie Paulo & Dean, thank you for your replies.  I had given up and was actually in the process of purging AspectJ from my project when they arrived.  So, I copied my AspectJ-free project to a new directory and used the Eclipse option to convert to AJ project.  I didn’t think your suggestions were going to help since the failure I had been getting were on the _expression_ “within(com.mycompany..*+)”; however, I tried anyway.
 
Amazingly, things seemed to behave exactly as they should.  With this happy event, I tried the tests from my original posting.  At the time of posting, the pointcut “within(com.mycompany..*+)” allowed 118 join points.  Now, it allows > 3000 which is approximately what I expected.
 
When I thought back on my installation within Eclipse 3.2.1, I downloaded AJDT from eclipse.org, extracted the file, copied the features to .../eclipse_3.2.1/features/, and copied the plugins to .../eclipse_3.2.1/plugins.  When I installed AJDT for Eclipse 3.3M5, I used the feature installer.  Is it possible that an improper installation the first time caused my AJ project to be setup incorrectly and caused all my problems?
 
Due to my 4 days of pain, I am a bit timid at the moment; however, I want to believe that AJ is stable and reliable because
  
  1. it is used in a lot of projects
  2. it has the awesome power (for good or bad) to make massive changes to the code that I write


Thanks again for the responses,
Kevin
 
 

From: Kevin F <aj@xxxxxxxxxxxxxxxxxxxxxxx> <mailto:aj@xxxxxxxxxxxxxxxxxxxxxxx>
 Reply-To: <aspectj-users@xxxxxxxxxxx> <mailto:aspectj-users@xxxxxxxxxxx>
 Date: Sun, 25 Feb 2007 08:07:22 -0500
 To: <aspectj-users@xxxxxxxxxxx> <mailto:aspectj-users@xxxxxxxxxxx>
 Conversation: Frustrated Newbie
 Subject: [aspectj-users] Frustrated Newbie
 
 
I’ve been at this for 4 days now.  I had some good luck with a few initial cases where I was able to clean up some code and verify through testing it worked like a charm.  I made a couple minor tweaks to those which broke them giving the technology an unreliable feel.  I’m willing to write that off as inexperience.
 
So I continued on and tried to implement some simple enforcement policies that I read in the book from the Eclipse Series (trying to support development by buying products and all).  It isn’t working at all and my frustration level trying to implement even simple enforcement policies is off the scale.
 
Yesterday, I posted the following to the AspectJ newsgroup without a response yet.  I continued researching on my own, even using the latest milestone AspectJ release for Eclipse 3.3M5.  Still no luck.
 
---------------
Newsgroup post:
---------------
 
I'm new to AspectJ so please no flames.  I'm using AJDT for Eclipse 3.2.1
and have been following the details from the "eclipse AspectJ" book.
 
I'm trying to enforce simple errors such as "It is an error to implement any
listener interface unless you also implement interface Foo."  To do this, I
want to try:
 
pointcut listeners() : within(*..*Listener*+);
pointcut myCode() : within(com.mycompany..*+);
pointcut mySpecialInterface() : within(com.mycompany.Foo+);
declare error: listeners() && myCode() && !mySpecialInterface()
             : "All listeners must implement Foo";
 
 
Since this did not work, I tried various experiments.  So, I tried the
following:
 
declare error: within(*..*Listener*+)
             : "A";
declare error: within(com.mycompany..*+)
             : "B";
declare error: within(*..*Listener*+) && within(com.mycompany..*+)
             : "A intersect B";
declare error: within(*..*Listener*+ && com.mycompany..*+)
             : "A intersect' B";
declare error: within(*..*Listener*+) || within(com.mycompany..*+)
             : "A union B";
declare error: within(*..*Listener*+ || com.mycompany..*+)
             : "A union' B";
 
A seems to be tagged correctly on all classes that implement any interface
with the word Listener in its name.
 
B seems to tag only a fraction of the classes I have written.
 
A intersect B and A intersect' B both result in no tags.
 
A union B and A union' B both seem to result in the union of what A and B
tagged above.
 
 
AOP seems so powerful yet so cryptic.  Can anybody help?
 
 


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--
Dean Wampler's Signature Dean Wampler, Ph.D.
dean at aspectprogramming.com
objectmentor.com
aspectprogramming.com
contract4j.org

I want my tombstone to say:
Unknown Application Error in Dean Wampler.exe.
Application Terminated.