Possible Annotation Processor JavaC Bug
mark at talios.com
Fri Jun 8 18:45:27 PDT 2012
The problem we were trying to diagnose was mostly to do with a recent
change in the Apache Maven build tool, as part of the new
maven-compiler-plugin/plexus-javac-compiler releases, the same instance
of the javac compiler is reused across modules in a multi-module build.
This both lowers memory and increases the speed of a multi-module
Yesterday we introduced an annotation processor into one of those
modules, and found that even tho the jar containing the module wasn't
in the classpath of subsequent modules, the annotation processor was
still running as part of its build.
- top level project
- module a
> adds jar_with_processor
> processor runs
- module b
> processor also runs
No changes were made to the javac command line to specify or limit
which processors should be run, which causes javac to auto-discover
annotation processors based on their META-INF contents.
Looking thru the javac sources, it looked like this discovery process
is handled at construction time ( I can't recall off hand if this was
actually in the constructor, or just 'around' the construction ). We
did spot a context object which is reused over subsequent compilation
calls so I'm wondering if the processors to run are somehow tracked in
here, and not being reset/cleared with subsequent compilation jobs with
The maven-compiler-plugin also added options to fallback to always
creating a new instance of Javac , but I've not yet had a chance to
test that and see if that resolves the problem.
My guess is this is more a maven-plugin bug with its attempts at
Good to know the code in JavaCompiler is as intended, the
multi-assignment just jumped out at me as not looking overly kosher so
thought I'd query it :)
On Sat Jun 9 03:41:03 2012, Jonathan Gibbons wrote:
> What is your underlying "strange problem with annotation processors"?
> The code in JavaCompiler is as intended, and is not itself a javac bug.
> -- Jon
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