[wildfly-dev] Dynamically attaching AspectJ LTW weaver from EAR

[Eric B]

Thanks Stuart - I hadn't thought of that.

It does bring up a couple of questions/concerns though:
1) The AspectJ attach EJB would need to be in an independent module from
the rest of the application (minor detail)
2) The EJB required is of a singleton pattern.  How would that work in a
clustered environment?  A @Singleton @Startup EJB would only be spawned in
a single JVM - other nodes in the cluster won't trigger the @PostConstruct
method of it and consquently not load the weaver.

Is there a way to force eager initialization of a @Stateless bean instead?


Baring that, I did run across a blog entry that indicates the use of the
Observer pattern listening for the ApplicationScope (
https://rmannibucau.wordpress.com/2015/03/10/cdi-and-startup/).  But I
suspect that at that point the beans have already been scanned.

@ApplicationScoped
public class ProvisioningDataForApplicationLifecycle {
    private final Map<String, User> users = new HashMap<>(); // + getter

    public void init(@Observes @Initialized(ApplicationScoped.class) Object
init) {
        users.put("cdi", new User("cdi", "1.1"));
        users.put("deltaspike", new User("deltaspike", "1.3"));
    }

    public void destroy(@Observes @Destroyed(ApplicationScoped.class)
Object init) {
        users.clear();
    }
}



This seems fairly like a complex solution to a fairly simple ask.  Or am I
misunderstanding the @Singleton pattern?

Thanks,

Eric


On Wed, Oct 18, 2017 at 10:55 AM, Stuart Douglas <stuart.w.douglas at gmail.com
> wrote:

> So one possibility that comes to mind would be to create a small
> deployment that does the aspectJ attach on deploy (e.g. in a @PostConstruct
> method of an @Startup EJB).
>
> You could then add an inter-deployment dependency on this deployment to
> all your other deployments, which should ensure that this code is run
> before other modules are created/loaded.
>
> Stuart
>
> On Wed, Oct 18, 2017 at 4:00 AM, Eric B <ebenzacar at gmail.com> wrote:
>
>> Hi,
>>
>> I'm looking to use AspectJ Load Time Weaving with Wildfly 10.  Looking
>> around at some posts, it is a little complicated to get Wildfly launched
>> properly with the AJ weaver due to the way the AJ library intializes the
>> logging subsystem differently than WF.
>>
>> Digging around, I found a config that actually works.  It is documented
>> here (obviously some of the class names/versions have to change):
>> https://github.com/ChienChingLee/How-to-launch-Wild
>> fly-9.0-with-AspectJ-1.8-LTW
>>
>> But I'm not a fan of changing my conf file to something that has
>> hardcoded paths/jar names in it - for example adding:
>>  -Xbootclasspath/p:$JBOSS_HOME/modules/system/layers/base/
>> org/jboss/logmanager/main/jboss-logmanager-2.0.0.Final.jar
>>
>>
>> Digging around some more in AJ, I saw that as of AJ 1.8.7, there is a way
>> to dynamically attach the weaver to the JVM.  Very cool.
>> https://www.eclipse.org/aspectj/doc/released/README-187.html
>> But in order to use the LTW effectively, I need to ensure that the weaver
>> is loaded prior to WF scanning and loading any of my classes (EJB,
>> annotated beans, pojos, etc).  But I have no ideas how to do that.
>>
>> In the case of a console application, it is pretty straight forward -
>> make it the first item in the application's main() method.  But in the case
>> of a JEE app, I don't know of any main() equivalent.
>>
>>
>> Is there a way to hook into the classloading mechanism of WF instead to
>> tell it to load the weaver if it isn't already loaded?  Can this be done
>> from within the EAR deployment?  Or is there a single point of entry that
>> WF accesses before scanning any of the classes in the EAR?  Or is there a
>> simpler way of configuring or attaching the AJ Weaver?  I did find an old
>> ticket (https://issues.jboss.org/browse/WFLY-895) that related to this
>> issue, but it is marked as WONT FIX.
>>
>> Am not sure of the best approach at this point.
>>
>>
>> Thanks,
>>
>> Eric
>>
>> _______________________________________________
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>> wildfly-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/wildfly-dev
>>
>
>
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