Re: [aspectj-users] LTW and JRE classes

["Alexander Kriegisch" <alexander@xxxxxxxxxxxxxx>]

I tried '-verbose:class' both with normal LTW configuration and with the
weaving agent additionally prepended to the boot classpath via
'-Xbootclasspath/p:/my/path/aspectjweaver.jar"'. Except for the weaver
classes being loaded earlier in the latter case, the result is the same:

Only classes from AppClassLoader yield any AspectJ log message, woven or
not. JRE classes are being ignored, I see no other classloader being
attached. Actually there does not seem to be any specific debug logging
for names of attached classloaders at all, I only indirectly see things
like "[AppClassLoader@18b4aac2] debug not weaving 'a.b..C'".

-- 
Alexander Kriegisch
https://scrum-master.de


Andy Clement:

>> Furthermore, both '-verbose:class' and '-verbose=class' yield
>> warnings
> 
> That's not a weaver option, it is a JVM option for showing class
> loading. I thought pairing that with the -debug weaver option might
> show java types being loaded by the JVM and if there was no immediate
> weaver message then they weren't getting to the weaver.
> 
> It is interesting what classloaders weavers get attached to. I can't
> what the current class loader hierarchy is in Java8 - do you only see
> the one weaver attached to application related class loader?
> 
> 
> Alexander Kriegisch:
>
>> Actually, I am still running Java 8, so modules are not an issue
>> here.
>> 
>> Furthermore, both '-verbose:class' and '-verbose=class' yield
>> warnings:
>> 
>> [MethodUtil@1e51f2fa] warning Cannot configure weaver with option
>> '-verbose:class': unknown option
>> 
>> I run with these settings:
>> 
>> <weaver options="-showWeaveInfo -verbose -debug -Xset:weaveJavaxPackages=true,weaveJavaPackages=true">
>>   <include within="javax..*"/>
>>   <include within="java..*"/>
>>   <include within="org.aspectj..*"/>
>> </weaver>
>> 
>> I see nothing on the console indicating that any JRE classes are even
>> visible to the classloader. I even created a main class starting my
>> other main class via Class.forName(), Class.getMethod() and
>> Method.invoke() in order to avoid javax or java JRE imports in my
>> main class, trying to avoid that the weaver kicks in too late. It
>> seems as if the weaver does not get attached to the right
>> classloader. Should I do more than just '-javaagent:...' and also add
>> the weaver to the boot classpath or something?
>> 
>> I found a test related to javax classes, but that one is kinda
>> cheating because it tests with own classes in javax package not with
>> real JRE classes:
>> 
>> https://github.com/eclipse/org.aspectj/tree/master/tests/features160/weavingJavaxPackage
>> 
>> I really need some help to get started here.
>> 
>> 
>> Andy Clement:
>>
>>> I feel like they used to work but there were gotchas. For example
>>> the JVM loads up some types before the LTW infrastructure can even
>>> get involved and those can't be woven. I don't actually recall if we
>>> have testcases for this but I wouldn't be surprised if they weren't
>>> there. I guess you have tried them and they don't work - I wonder if
>>> you were test weaving something that would be loaded early? It would
>>> be interesting to attempt it with a -verbose:class and verify not
>>> attempting to weave things loaded before the 'LTW is active' type
>>> messages come out. Will it work with modules in recent Javas? That
>>> seems unlikely.
>>> 
>>> But it could be the kind of classloaders in use in regular Java now
>>> don't allow weaver attachment, I honestly haven't kept up to speed
>>> on that - and maybe that prevents them working at all. A run of LTW
>>> with the debug option on for the weaver should show the types the
>>> weaver is being exposed to. If those are java/javax then they should
>>> be weavable.
>>> 
>>> 
>>> Alexander Kriegisch:
>>> 
>>>> The AspectJ documentation still mentions things like
>>>> 
>>>> -Xset:weaveJavaxPackages=true
>>>> -Xset:weaveJavaPackages=true
>>>> 
>>>> or for LTW
>>>> 
>>>> <include within="javax.*"/>
>>>> <include within="java.*"/>
>>>> <include within="org.aspectj.*"/>
>>>> 
>>>> (I think "java..*" would be correct syntax, BTW.)
>>>> 
>>>> None of these work. Yes, there are valid cases in which users might
>>>> want to use LTW on JRE classes. The only way I could ever weave
>>>> into the JRE (execution joinpoints, not just call from my own woven
>>>> code) was binary weaving and creating my own (subset of) JRE,
>>>> prepending it to the boot classpath. But that's not nice and I
>>>> never tried with modularised Java 9+, which might work or not.
>>>> 
>>>> Before I create a Bugzilla ticket I would like to get a maintainer
>>>> opinion. Is there any chance to make this work with AspectJ LTW? Is
>>>> is maybe possible already and I just do it wrong?