Hi Mohammad,
nope, unfortunately AspectJ is not able to declare fields "dynamically",
moreover private fields injected by AspectJ have a number of limitations
that are being solved (they have mangled names).
What you can do however is :
- Declare an interface WithObserverABC
- Use an ITD to place a privare field on that interface
- Inject that interface on all classes that have @Observable
- Write the aspect that calls the observer method when an @Observable method
is executed.
public aspect InjectObserverABC {
public interface WithObserverABC {}
// this could be private, except for name mangling, depends on AspectJ
version
public ObserverAbc WithObserverABC.abcObserver = new ObserverABCImpl();
// you could narrow this
declare parents : hasmethod(@Observable *(..)) implements WithObserverABC;
before(WithObserverABC instance) : execution(@Observable *
WithObserverABC+.*(..)) && this(instance) {
instance.abcObserver.
notifyObserver();
}
}
I'm not sure about the syntax (I wrote it here in this email, and i need
compiler support when writing pointcuts :) ), but you should get the idea.
Eventually you can try to play with generics/abstract aspects to make it
easier to inject new observers, but I cannot think of a way of doing this
completely automatically (apart from using APT to parse classes with
@Observer and generate dynamically aop.xml to instantiate concrete aspects
... but that's another story :) )
Hope this helps,
Simone
2010/4/20 Mohammad Norouzi <[email protected]>
> Hi Simone,
>
> >>if I understand correctly, when a method annotated with @Observable is
> executed, you want to see if there are fields in that class with an instance
> of an observer, and call a method on the observer.<<
> Actually, when a method is annotated with @Observable (before executing and
> at the time of compiling codes) I want to add (not see) those interfaces
> that annotated with @Observer, as private fields in the observable and I
> want to add them because both observer and observable are EJB session beans
> so the application server will take the burden of instantiating those
> observers using its injection technique
>
> What I need is something like this:
> for(MyObserver o : observers){
> declare a private field with a name in this instance of observable class
>
> }
>
>
> On Mon, Apr 19, 2010 at 2:22 PM, Simone Gianni <[email protected]> wrote:
>
>> Hi Mohammad,
>> if I understand correctly, when a method annotated with @Observable is
>> executed, you want to see if there are fields in that class with an instance
>> of an observer, and call a method on the observer.
>>
>> You can use AspectJ to execute an advice before/after/around the execution
>> of @Obervable methods, and use thisJoinPoint or the this() construct to find
>> the instance of the method.
>>
>> Once you are there, you must use plain java reflection, and not AspectJ,
>> to find fields in that class that contains an observer and invoke observer
>> methods.
>>
>> To add @EJB annotation to all fields of type X where X is annotated with
>> @Observer, you can use declare @class and write a type pattern that uses
>> @Observer annotation. If @Observer annotation is placed on methods, you can
>> use hasmethod() to find classes that has such methods, but beware cause
>> hasmethod is somewhat experimental.
>>
>> Hope this helps,
>> Simone
>>
>> 2010/4/19 is_maximum <[email protected]>
>>
>>
>>> Thanks Simone, yes this is exactly what I want... but another question is
>>> that this is used using 'declare' and as far as I know declare is placed
>>> in
>>> aspect definition. How can I place it in a for-loop.
>>>
>>> Let me tell you the scenario may be I am in wrong way...
>>>
>>> I am trying to implement an observer pattern in EJB 3.0. I saw many
>>> implementation using aspectJ but mine is a little different. The
>>> difference
>>> is that I want to inject observer into observable...
>>>
>>> Because session beans are managed object and in my case both observer and
>>> observable supposed to be session beans I want application server injects
>>> observer session beans in observable SB and then call observer methods
>>>
>>> These observer and observable methods will be annotated by the developer
>>> with say @Observer and @Observable
>>>
>>> What I wanted was to look for @Observer methods and find their interface
>>> and
>>> put them like this:
>>>
>>> @EJB
>>> private ObserverInterface1 observer1
>>>
>>> than each time the determined method is called I can call
>>> observer1.notifyObserver() method
>>>
>>> Can you please help me on this?
>>>
>>>
>>>
>>>
>>> Simone Gianni-2 wrote:
>>> >
>>> > Hi Mohammad,
>>> > maybe you are loooking for the declare annotation statement?
>>> >
>>> http://www.eclipse.org/aspectj/doc/next/adk15notebook/annotations-declare.html
>>> >
>>> > Simone
>>> >
>>> >
>>>
>>>
>>> -----
>>> --
>>> Regards
>>>
>>> Mohammad Norouzi
>>>
>>> Help each other to reach the future faster
>>>
>>> http://pixelshot.wordpress.com Pixelshot Photoblog
>>>
>>> http://brainable.blogspot.com Brainable Blog
>>>
>>>
>>> --
>>> View this message in context:
>>> http://old.nabble.com/How-to-rewrite-a-class-with-AspectJ-tp28280867p28287273.html
>>> Sent from the AspectJ - users mailing list archive at Nabble.com.
>>>
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>>
>>
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