I did try with my aspect.jar on the bootclasspath with -Xbootclasspath/a (I
would be surprised if /a or a /p would make a difference). Didn't make
any difference.
I haven't tried posting on StackOverflow yet figuring that I would likely
get a more targeted response from here or the wildfly-dev forums. But to
date, it's tough to reconcile information from the two independent camps. :)
I suspected that AJ just uses whatever classloader is provided to it.
That's kind of what it looked like to me. But I couldn't/don't understand
how the Agent bootstraps though. From what I can tell, its the base JVM's
classloader that calls the Agent premain, and instructs it to instrument
the classes. In which case, I would expect any visibility of that
classloader to extend to AJ as well.
So given that the AJ Weaver doesn't find the classes, I figure that WF is
doing something with/to it. But in that case, I dont understand at all how
the JVM's instrumentation works; I guess I'm confused where in the cycle
the instrumentation is called when loading classes. Do you know if there
are any docs or whitepapers I can read up on how the
classloader/instrumentation cycle works? I couldn't find enough clarity on
the Oracle site.
Thanks,
Eric
On Thu, Oct 26, 2017 at 3:07 PM, Andy Clement <andrew.clem...@gmail.com>
wrote:
> Did you try your aspect jar on the bootclasspath ? (Just wondering if that
> might help).
>
> AspectJ deliberately avoids getting involved in class loader shenanigans
> because it gets too complicated, hence relying on the delegation model in
> place for the system it is being used with. However you make a ‘common
> jar’ available to all the individual module loaders in wildfly should work
> for AspectJ, unless they are handling delegation for classes differently to
> delegation for resource access. I don’t feel this is a new problem though,
> I feel it has come up again and again over the years - surely somebody
> solved it by now.... Did you try stack overflow? Sorry i don’t have any
> concrete answers.
>
> cheers,
> Andy
>
>
> On Oct 26, 2017, at 11:37 AM, Eric B <ebenza...@gmail.com> wrote:
>
> Thanks for the info. I've been digging through AJ and WF code some more
> to try to figure this out, but am still not sure how the classloader is
> working. I'm starting Wildfly using the following arguments:
>
> -Djboss.modules.system.pkgs=org.jboss.byteman,org.aspectj,te
> st.aspectj,org.jboss.logmanager
> -javaagent:c:/dev/tmp/jboss-eap-7.0.0/modules/system/layers/
> base/org/aspectj/main/aspectjweaver-1.8.10.jar
> -Dorg.aspectj.weaver.showWeaveInfo=true"
> -Dorg.aspectj.weaver.loadtime.configuration=file:c:/tmp/poc/aop.xml
> -cp C:/dev/Projects/jms/mixed-arch/ear-app/aspectj/target/aspect
> j-0.0.1-SNAPSHOT.jar
>
>
> So in it, I've defined an additional classpath pointing to my aspectj.jar
> file. My /tmp/poc/aop.xml contains the aspect definition of "
> test.aspectj.TestAspect".
> I can now see that the AJ agent is looking for test.aspectj.TestAspect
> class. But it still isn't able to find it; I get the following errors
> thrown my the AspectJ Weaver:
>
> 2017-10-26 12:11:39,889 ERROR [stderr] (MSC service thread 1-7)
> [ModuleClassLoader@336f62a1] info register aspect test.aspectj.TestAspect
> 2017-10-26 12:11:54,632 ERROR [stderr] (MSC service thread 1-7)
> [ModuleClassLoader@336f62a1] error The specified aspect
> 'test.aspectj.TestAspect' cannot be found
>
> I've confirmed that my class (test.aspectj.TestAspect) is indeed in the
> aspectj-0.0.1-SNAPSHOT.jar.
>
> So I get the impression that the aspectj-SNAPSHOT jar is not being made
> visible to the individual module classloaders. I've tried to debug the
> weaver, and can see that it does indeed do the following:
>
> private URL toURL(String className) {
> URL url = (URL) nameMap.get(className);
> if (url == null) {
> String classFile = className.replace('.', '/');
> url = loaderRef.getClassLoader().getResource(classFile + ".class");
> nameMap.put(className, url);
> }
> return url;
> }
>
> where the loaderRef.getClassLoader() looks like it is the classloader that
> is passed to the ClassFileTransformer.transform() method (
> https://docs.oracle.com/javase/7/docs/api/java/lang/instrum
> ent/ClassFileTransformer.html). But I'm not sure where/how to continue
> digging from here. Which classloader is this? Is this the base java
> classloader? If Wildfly defines its own classloader (not sure if it does),
> will it be used instead? On the other hand, if the base java classloader
> is passed, why is the classloader not able to find my
> test.aspectj.TestAspect class if it is in the jar that is part of my -cp
> arguments?
>
>
> Thanks,
>
> Eric
>
> On Mon, Oct 23, 2017 at 1:45 PM, Andy Clement <andrew.clem...@gmail.com>
> wrote:
>
>> Yes, it is a bit specific to wildfly but I can talk to what AspectJ
>> does. I will also call out to an old article I wrote on debugging LTW:
>> http://andrewclement.blogspot.ca/2009/02/load-time-weaving-basics.html (might
>> be useful).
>>
>> In the source for ClassLoaderWeavingAdaptor you will see three options
>> for files we look for:
>>
>> META-INF/aop.xml — the regular one
>> META-INF/aop-ajc.xml — another option, useful in case you are using
>> -outxml to generate the XML and don’t want to damage some user config you
>> are maintaining (keep user stuff in aop-ajc.xml)
>> org/aspectj/aop.xml — for OSGi usage but not specific to OSGi, can be
>> used in other scenarios.
>>
>> Also in the same class you’ll see:
>>
>> *private* *final* *static* String *AOP_XML* = Constants.*AOP_USER_XML* +
>> ";" + Constants.*AOP_AJC_XML* + ";" + Constants.*AOP_OSGI_XML*;
>> String resourcePath = System.getProperty("org.aspect
>> j.weaver.loadtime.configuration", *AOP_XML*);
>>
>> So you can override those 3 places and give it the path to something else
>> if you want to by specifying that property. If the thing you provide starts
>> with file then it will actually load direct from there:
>>
>> *if* (nextDefinition.startsWith("file:")) {
>> *try* {
>> String fpath = *new* URL(nextDefinition).getFile();
>> File configFile = *new* File(fpath);
>>
>> If you just run default then it will be making calls to
>> getClassLoader().getResources(name); for those three variants above. So
>> you are at the mercy of whatever the class loader is allowing you to see.
>>
>> cheers,
>> Andy
>>
>> On Oct 21, 2017, at 7:19 PM, Eric B <ebenza...@gmail.com> wrote:
>>
>> So this is probably more of a Wildfly question than an AspectJ question
>> as such, and I have already asked the Wildfly team about it, but I thought
>> I would try to get additional clarity from the AJ pros to understand
>> exactly how the LTW agent works.
>>
>> My use case is that I want to use use AspectJ to advise some core classes
>> in Wildfly/undertow. Specifically, I'm trying to advise some of the
>> Undertow HttpSession methods to get some more detailed logging when
>> Sessions are created/expire/etc.
>>
>> To that extent, I've added AspectJ as a -javaagent which is launched on
>> startup of Wildfly. I had to follow some of the steps listed at:
>> https://github.com/ChienChingLee/How-to-launch-Wildfly-9.0-
>> with-AspectJ-1.8-LTW. But it works; I can see that the AJ weaver is
>> loaded and present.
>>
>> My problem now has to do with the way that the Wildfly classloaders
>> work. From my understanding, to avoid class conflict issues, the
>> Application Server is designed such that everything is broken down into
>> individual modules, with a separate classloader for each module. Modules
>> can declare dependencies on other modules if they truly want/need to access
>> classes defined in a different module (see https://docs.jboss.org/au
>> thor/display/WFLY10/Class+Loading+in+WildFly)
>>
>> I've tried to configure AJ to have the loader available to all modules,
>> so now my question is how does AJ detect Aspects in the classpath?
>> Where/how does it search for the aop.xml file? Does the weaver search
>> every jar that is in the classpath for these files? How does it determine
>> which files to scan in the classpath? Does it simply delegate that to the
>> classloader? (ie: Class.getResourceAsStream("aop.xml"))? I haven't dug
>> through the AJ code to see exactly what it does.
>>
>> Right now, I'm a little stuck in that I'm not sure how to ensure that my
>> Aspects are loaded with every module in WF. I've managed to reconfigure a
>> single module and it works, but the idea of reconfiguring every module
>> individually doesn't make sense.
>>
>> I tried to create an independent module in WF for it, and declaring it as
>> a global module but that didn't seem to work.
>>
>> I tried to add it to the startup parameters in the WF startup
>> configuration file, specifying it as -classpath path/to/myaspect.jar, but
>> that only advised the startup WF (org.jboss) classes and none of the
>> modules.
>>
>> Can anyone shed some more light how the LTW works in order to search/find
>> and weave classes? Or if anyone has any brilliant ideas how I can
>> configure my WF server such that I can drop my asepcts.jar in a "generic"
>> place to make it woven into every module, I would appreciate it.
>>
>> Thanks!
>>
>> Eric
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