Annotation discovery JEP

[arjan tijms]

I'm absolutely in favour of this! This would help a lot.

On Fri, Dec 1, 2017 at 3:57 PM, Stephen Colebourne <scolebourne at joda.org>
wrote:

> I believe this would be a very valuable addition.
> Stephen
>
>
> On 1 December 2017 at 14:44, Greg Wilkins <gregw at webtide.com> wrote:
> > All,
> >
> > I'm not at all familiar with your processes here, but it has been
> suggested
> > to me that I should
> > create a JEP to try to initiate a common effort to standardise annotation
> > discovery.
> >
> > I have created a draft JEP
> > <https://github.com/jetty-project/annotation-discovery/
> blob/master/JEP-Proposal.md>,
> > which is very light on detail, but I hope it at least well captures the
> > motivation, reproduce here:
> >
> > *Motivation*
> >
> > Prior to Java 9, many java technologies implemented annotation discovery
> by
> > inspection of either the URLs of the classloader and/or the class path
> > itself and tools such as ASM where then used to parse the byte code for
> > annotations without loading the classes. With the introduction of java 9,
> > which included Modules, Layers, Upgrade paths, Jlink and Multi Release
> > jars, the task of discovering class has become difficult to both specify
> > and implement.
> >
> > Efficient annotation discovery was an identified requirement of project
> > Jigsaw
> > <http://openjdk.java.net/projects/jigsaw/spec/reqs/#
> efficient-annotation-detection>
> > :
> >
> > *It must be possible to identify all of the class files in a module
> > artifact in which a *
> >
> > *particular annotation is present without actually reading all of the
> class
> > files. *
> >
> > *At run time it must be possible to identify all of the classes in a
> loaded
> > module *
> >
> > *in which a particular annotation is present without enumerating all of
> the
> > classes *
> >
> > *in the module, so long as the annotation was retained for run time. For
> > efficiency it *
> >
> > *may be necessary to specify that only certain annotations need to be
> > detectable in *
> >
> > *this manner.*
> >
> >
> > However as explained in the mailing list, this requirement "didn't happen
> > in Java SE 9
> > <http://mail.openjdk.java.net/pipermail/jigsaw-dev/2017-
> November/013363.html>".
> > Thus currently multiple frameworks (servlets, EJB, JPA, CDI, Spring etc.)
> > are currently reverse engineering the algorithms implemented by the JVM
> for
> > resolving the modules available at runtime and which classes within those
> > modules are available for loading by the specific runtime platform. Such
> > duplicated effort is unlikely to be correct given the complex nature of
> > module resolution, nor future proof given the intention to release java
> 10
> > and 11 within the next year.
> >
> >
> > I'd appreciate any feedback on the form or substance of this proposal
> > before I submit it
> >
> > regards
> >
> > --
> > Greg Wilkins <gregw at webtide.com> CTO http://webtide.com
>