Re: [aspectj-users] LTW, inter-type fields and pertarget() aspects

[Jochen Wuttke <jochen.wuttke@xxxxxx>]

Thanks Andy and Simone,

I think I understand the basic idea now. But apparently something is  
not yet working for me.
Here's an aspect that uses two ITDs, which do not get woven using LTW  
and thus cause a NosuchField exception (I get weave info on the method  
advice, but not the ITDs). As you can see it is pretty much the same  
as the one using pertarget(), and I'd like to understand if I'm doing  
something wrong, or if there's some sort of bug that prevents me from  
using ITD fields.


public aspect JspIdConsumerUnique {
	
	private boolean UIComponentClassicTagBase.lumi_uniquePropertySet =  
false;
	private Object UIComponentClassicTagBase.uniqueProperty = null;

	pointcut instanceCreation( UIComponentClassicTagBase _consumer ):  
this(_consumer) && execution( UIComponentClassicTagBase+.new(..) );
		
	after(UIComponentClassicTagBase _consumer) :  
instanceCreation( _consumer ) {
		safeAddObject( _consumer );
	}
	
	pointcut setUniqueProperty( UIComponentClassicTagBase _consumer ):  
target(_consumer) &&
		call( * UIComponentClassicTagBase+.setJspId(..) );
	
// ITD USED HERE
	before( UIComponentClassicTagBase _consumer ):  
setUniqueProperty( _consumer ) {
		if ( _consumer.lumi_uniquePropertySet ) {
			_consumer.uniqueProperty = _consumer.getJspId();
		}
	}
	
//AND HERE
	after( UIComponentClassicTagBase _consumer ):  
setUniqueProperty( _consumer ) {
		if ( propertyHasChanged( _consumer.uniqueProperty,  
_consumer.getJspId() ) ) {
			_consumer.lumi_uniquePropertySet = true;
			updateContainer( _consumer.uniqueProperty, _consumer );
		}
	}
	
	//private methods go here
}


Thanks again,
Jochen


On Oct 14, 2008, at 11:14 PM, Andy Clement wrote:

> > - Shouldn't a pertarget/perthis aspect declare field pretty much  
> the same way as an inter-type declaration in a singleton aspect?
> Sometimes.  The instantiation model of the aspect won't affect the  
> application of static crosscutting.  An intertype field declaration  
> onto some type will apply for all instances of that type, not just a  
> subset that might be selected by the instantiation model - so the  
> fields will always be there, but when they are used depends on your  
> advice.  perthis()/pertarget() allow for even finer grained control  
> over the state lifecycle where you want some state to exist for just  
> a subset of the join points that occur during execution.
>
>
> Andy.
>
> 2008/10/14 Jochen Wuttke <jochen.wuttke@xxxxxx>
> Hi,
>
> I started playing with LTW, inter-type fields and pertarget()  
> aspects and ran into an interesting problem.
> I was trying to use inter-type fields to carry some information I  
> need on a per-object basis. But every time the advice using these  
> inter-type fields got executed I got a NoSuchFieldException (the  
> compiler gave me a typeNotExposedToWeaver warning, but I think  
> that's ok, because I use LTW). So I changed my aspect to be  
> pertarget() and it behaves like expected (aspect code below).
>
> Now here are my questions:
> - Shouldn't a pertarget/perthis aspect declare field pretty much the  
> same way as an inter-type declaration in a singleton aspect?
> - I'm not sure if I should use a pertarget or perthis aspect for  
> what I want to do. The content of the fields should be carried  
> around with the advised object across the objects lifetime (which is  
> why I originally wanted to use inter-types).
> - When running the LTW with -showWeaveInfo I get a log message for  
> every jointpoint that gets woven. What should the message look like  
> for weaving inter-type fields. Or should there be a message at all?
>
> Thanks,
> Jochen
>
> P.S.: My aspect looks like this:
>
> public aspect JspIdConsumerUnique  
> pertarget( instanceCreation(UIComponentClassicTagBase) ||  
> setUniqueProperty(UIComponentClassicTagBase) ) {
>
>        private boolean lumi_uniquePropertySet = false;
>        private Object lumi_uniqueProperty = null;
>
>        pointcut instanceCreation( UIComponentClassicTagBase  
> _consumer ): target(_consumer) &&  
> execution( UIComponentClassicTagBase+.new(..) );
>
>        after(UIComponentClassicTagBase _consumer) :  
> instanceCreation( _consumer ) {
>                safeAddObject( _consumer );
>        }
>
>        pointcut setUniqueProperty( UIComponentClassicTagBase  
> _consumer ): target(_consumer) &&
>                call( * UIComponentClassicTagBase+.setJspId(..) );
>
>        before( UIComponentClassicTagBase _consumer ):  
> setUniqueProperty( _consumer ) {
>                uniqueProperty = _consumer.getJspId();
>        }
>
>        after( UIComponentClassicTagBase _consumer ):  
> setUniqueProperty( _consumer ) {
>                if ( propertyHasChanged( _consumer.getJspId() ) ) {
>                        lumi_uniquePropertySet = true;
>                        updateContainer( uniqueProperty, _consumer );
>                }
>        }
>
>        //private methods go here
>
> }