Spring's need for optional dependencies

[Paul Benedict]

That doesn't bode well for frameworks that must run in JDK 8 and 9 --
either in classpath mode or module mode. That means the addReads() call
will have to be reflective so it can work in both worlds. That's just
another hack.

Cheers,
Paul

On Fri, Dec 18, 2015 at 11:33 AM, Neil Bartlett <njbartlett at gmail.com>
wrote:

> I do not see any statement in the Module System Requirements document (
> http://openjdk.java.net/projects/jigsaw/spec/reqs/) such that Java 9 is
> required to be backwards compatible, except where code runs in “classpath
> mode” (aka the unnamed module).
>
> Therefore it is an acceptable solution — at least if you accept the
> Requirements! — to need explicit API calls such as addReads() in frameworks
> when running in module mode.
>
> Regards,
> Neil
>
> > On 18 Dec 2015, at 16:14, Paul Benedict <pbenedict at apache.org> wrote:
> >
> > Adding read edges at runtime is not a backward compatible solution.
> Jigsaw
> > should automatically allow you to read anything your Module Descriptor
> > gives you access to -- required or optional.
> >
> > Cheers,
> > Paul
> >
> > On Fri, Dec 18, 2015 at 10:02 AM, Peter Levart <peter.levart at gmail.com>
> > wrote:
> >
> >>
> >>
> >> On 12/18/2015 04:49 PM, Peter Levart wrote:
> >>
> >>> You can check whether the optional module is included in a runtime
> >>> configuration or not with a simple Class.forName() check even if you
> don't
> >>> depend on the module (i.e. don't list it in "requires" descriptor at
> >>> runtime). The visibility of classes is not restricted. It only depends
> on
> >>> ClassLoader hierarchy. When you successfully resolve some optional
> class at
> >>> runtime (with Class.forName), you then have to add a read edge to it's
> >>> module:
> >>>
> >>>    Class<?> optionalClass = Class.forName("...");
> >>>    MySelfClass.getModule().addRead(optionalClass.getModule());
> >>>
> >>> ...before invoking any code that uses this module.
> >>>
> >>
> >> Just had an idea!
> >>
> >> Optional dependency at runtime could add a read edge to the module if
> that
> >> module was included in the configuration, but would otherwise not cause
> >> that module to be included in the configuration by itself. How does that
> >> sound? Spring would work as before - no .addRead() calls needed. Just
> >> Class.forName("OptionalClass").
> >>
> >> Regards, Peter
> >>
>
>