rmannibucau commented on pull request #65:
URL: https://github.com/apache/openjpa/pull/65#issuecomment-663085420
@dazey3 yep, the one mentionned on the list and the PRs:
tmploader==apploader. The toggle just disable enhancement under some setups
(close to openliberty ones where the load class goes into the apploader which
implements itself the transformer). That said you have a very good point that
JVM instrumentation does not need that since it skips by itself the nested
enhancement so seems it is only appearing on custom classloaders in app servers
(like tomcat or openliberty).
So overall it seems it means that it is an application server bug that this
boolean is needed.
Regarding the exclude list vs boolean: the exclude list makes the behavior
deterministic vs the boolean depends which classes where touched or not before
which is way less deterministic and error prone so between both I prefer the
exclude list to at least guarantee the understanding is unique.
However, in regards to previous point it seems we should just drop this as a
default behavior and use a config to have a nested exclusion for buggy servers
for compatibility only.
Concretely it would be something like: if
"openjpa.agent.preventNestedTransformations=true" then we wouldnt use
PCClassFileTransformer but HarnessedPCClassFileTransformer which would fully
delegate to PCClassFileTransformer but transform method*s* would be wrapped in
with this boolean:
if (transforming.get() != null) return null;
transforming.set(true);
try {
delegate.transform();
} finally {
transforming.remove();
}
This way we handle buggy impls with a flag but our default is sane and
aligned on the JVM.
Long term we can report the bugs in the app servers and make them properly
fix it (it is not limited to openjpa).
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