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RE: [aspectj-users] Overriding pointcuts

Load-time weaving has some great options if you want to modify the behavior at deployment time rather than runtime, as Wes says. There is also a bit of overhead required on staticinitialization (when loading classes that might be recorded), but at the point you reach the join point the test is very efficient. Here’s an example compiled with AspectJ 1.5.2. The runtime overhead on executing the method is limited to invoking a static method that reads a field and branching. I believe most VM’s will actually inline this test since the called method is static (that’s why it’s worth benchmarking). As Wes indicates, there should be very little overhead involved.

 

public aspect Recorder {

    public static boolean enabled = false;

 

    before() : execution(* domain..*(..)) && if(enabled) {

        // simulate recording

        for (int i=0; i<thisJoinPoint.getArgs().length; i++) {

             System.err.println(thisJoinPoint.getArgs()[i].toString());

        }

    }

}

 

package domain;

 

public class Sample {

    public void foo() {}

}

 

javap -c domain.Sample

 

public void foo();

  Code:

   0:   invokestatic    #42; //Method Recorder.ajc$if_0:()Z

   3:   ifeq    20

… (code that runs if enabled)

   20:  return

 

static {};

  Code:

   0:   new     #27; //class org/aspectj/runtime/reflect/Factory

   3:   dup

… (setting up data structures such as join point static parts)

 

javap -c Recorder

 

public static final boolean ajc$if_0();

  Code:

   0:   getstatic       #16; //Field enabled:Z

   3:   ireturn

 


From: aspectj-users-bounces@xxxxxxxxxxx [mailto:aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Wes
Sent: Wednesday, September 06, 2006 11:35 AM
To: aspectj-users@xxxxxxxxxxx
Subject: RE: [aspectj-users] Overriding pointcuts

 

Hi Savita -

 

If you'd like the deployer of aop.xml to be able to enable or disable the flight recorder entirely

when the application is loaded, declare the aspect abstract, and then have the deployer declare

a concrete subaspect in aop.xml if s/he wants it enabled. 

 

That's different from making the pointcut fail at runtime by relying on a boolean flag.  The flag

is preferable where you want to enable and disable the flight recorder while the program is

running, as Ron suggested with JMX.  Ron's correct to point out that JoinPoint, the reflective

representation of a join point available in the body of advice, has of late become constructed

lazily (by default, I believe), so you can avoid that overhead if there is no other advice on that

join point.  But I believe the runtime still needs to setup for evaluating the join point and advice

and do the test (but this should be minimal -- certainly as efficient as hand-coding).

 

Wes

 

------------Original Message------------

From: "Ron Bodkin" <rbodkin@xxxxxxxxxxxxxx>

To: aspectj-users@xxxxxxxxxxx

Date: Wed, Sep-6-2006 10:56 AM

Subject: RE: [aspectj-users] Overriding pointcuts

Savita you can significantly reduce the overhead by dynamically enabling and disabling your aspects. This can be as simple as using the if pointcut like so

 

public aspect FlightRecorder {

    private static boolean enabled; // can be controlled through JMX, for example

 

    public pointcut flightMethod():

        execution(!@PrimitiveDataLoggerAnnotation public * *.Method*(..));  

    private pointcut recordedMethod(): if(enabled) && flightMethod();


    before() : recordedMethod() { … }

    after() : recordedMethod() { … }

}

 

AspectJ constructs join points lazily when they are guarded like this, so you should see the runtime overhead as simply the time for a single (inlined) if test. This is often desirable, especially if you would like to be able to enable and disable recording at runtime. You can also allow more dynamic scoping e.g., by package and class like with logging frameworks, possibly also with a global enabled switch. AspectJ been tuned significantly over the years to support efficiently running when aspects like this are disabled, but certainly you should benchmark the overhead in your case.

 

Ron

 

 

 

 

 

       

 


From: aspectj-users-bounces@xxxxxxxxxxx [mailto:aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Chandan, Savita
Sent: Wednesday, September 06, 2006 10:22 AM
To: aspectj-users@xxxxxxxxxxx
Subject: RE: [aspectj-users] Overriding pointcuts

 

Mathew,

Thanks for your response. That's a bummer. Lets look at the problem from a different  vantage point.

 What Iam trying to accomplish here is turn off the flight recorder logging with some configuration, without recompiling. I can do this by turning it off in the flight recorder, but then I will be taking the hit of AspectJ framework ( creating JoinPoints etc), which I dont want.

 

Rephrasing the question, Is it possible to turnoff AspectJ framework in the code without recompiling, by an off/on switch?

 

Thanks,

Savita

 


From: aspectj-users-bounces@xxxxxxxxxxx [mailto:aspectj-users-bounces@xxxxxxxxxxx] On Behalf Of Matthew Webster
Sent: Wednesday, September 06, 2006 3:18 AM
To: aspectj-users@xxxxxxxxxxx
Subject: Re: [aspectj-users] Overriding pointcuts


Savita,

Unfortunately this won't work because you can only extend abstract aspects so you cannot override the behaviour of an existing woven concrete aspect. You can override a pointcut but only in a sub-aspect:

public abstract aspect AbstractPrimitiveFlightRecorder {

        protected pointcut myMethod() :
                PrimitiveFlightRecorderPointcutLibrary.recordedMethod();

}

public aspect PrimitiveFlightRecorderAspect extends AbstractPrimitiveFlightRecorder
{
        protected pointcut myMethod()
        :   execution(!@PrimitiveDataLoggerAnnotation public * *.Method*(..));  

        before (): myMethod() {
                System.out.println("> PrimitiveFlightRecorderAspect.before() " + thisJoinPoint);
        }
       
        after (): myMethod() {
                System.out.println("< PrimitiveFlightRecorderAspect.before() " + thisJoinPoint);
        }
}

However one solution is to use a separate pointcut library which is used to weave at compile-time:

public aspect PrimitiveFlightRecorderPointcutLibrary {

        protected pointcut recordedMethod() :
                execution(@PrimitiveDataLoggerAnnotation public * *.Method*(..));

}

public aspect PrimitiveFlightRecorderAspect
{
        protected pointcut myMethod() :
                PrimitiveFlightRecorderPointcutLibrary.recordedMethod();

        before (): myMethod() {
                System.out.println("> PrimitiveFlightRecorderAspect.before() " + thisJoinPoint);
        }
       
        after (): myMethod() {
                System.out.println("< PrimitiveFlightRecorderAspect.before() " + thisJoinPoint);
        }
}

Then for LTW substitute an alternative implementation of the library. Because _all_ aspects must be woven, including those woven previously, you will pick up the new pointcut definition. Unfortunately you cannot define pointcut libraries using XML.

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/[1]

"Chandan, Savita" <Savita.Chandan@xxxxxxxxxxxxxx>
Sent by: aspectj-users-bounces@xxxxxxxxxxx

06/09/2006 02:43

Please respond to
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Subject

[aspectj-users] Overriding pointcuts

 

 

 




Hi,

I want to override pointcuts inserted in the aspect code during compile, at run time. What would I do to achieve this? If I created a pointcut in aop.xml that contradicts the pointcut inserted in the code, what would happen?

For ex.

In my aspect class
public aspect PrimitiveFlightRecorderAspect

{

       
pointcut myMethod():  execution(@ PrimitiveDataLoggerAnnotation public * *.Method*(..)) );

        before (): myMethod() {
       
}

        after (): myMethod() {}
}

Now if in the aop.xml if I were to do this. (pardon me for any mistakes in the aop.xml, this is the first time I creating one)  what would happen?

<aspectj>
       <aspects>
               <aspect name="
PrimitiveFlightRecorderAspect"/>
                 
pointcut myMethod():  execution(! @ PrimitiveDataLoggerAnnotation public * *.Method*(..)) );

        </aspects>
</aspectj>
Thanks,
Savita
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