More flexibility in providing services from modules?

[Tom De Wolf]

Hi Alex,

1 of the smaller suggestions in my blogpost (
https://devcreativity.wordpress.com/2019/03/02/java-modules-wish-list-provide-services-using-lambda-functions-and-more/)
was
to pass in the class of the expected service type as a parameter into the
provider method if the signature is defined with a Class as single
parameter. This little extension of the convention would allow already a
lot more flexibility. Would it be possible to consider it?

Thanks,

Tom
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Op ma 4 mrt. 2019 om 21:27 schreef Alex Buckley <alex.buckley at oracle.com>:

> Hi Tom,
>
> Nice to see thoughts about modular services.
>
> FYI Jigsaw's goals in this area were quite limited
> (http://openjdk.java.net/projects/jigsaw/spec/reqs/#services) and the
> static provider method was a relatively late add-on
> (http://openjdk.java.net/projects/jigsaw/spec/issues/#services).
>
> I agree that a static provider method offers a basic level of
> indirection (e.g. multiple `provides` directives can employ the same one
> if its return type implements multiple services) but it doesn't add much
> in the way of abstraction (e.g. over the desired service). This isn't
> the only place where ServiceLoader suffers from a lack of abstraction:
> you can't parameterize services because there's no way to request an
> implementation of a parameterized service (i.e. you can't say
> `ServiceLoader.load(ServiceA<Foo>.class)`).
>
> Frankly, we are not likely to revisit any of these limitations in the
> near future, but I think that ServiceLoader will always be a handy
> built-in option for limited use cases.
>
> Alex
>
> On 3/2/2019 9:19 AM, Tom De Wolf wrote:
> > The current ServiceLoader mechanism and Java Modules have a limited set
> of
> > options to provide an instance for a service from a module. Or you use
> the
> > constructor, or you use a static 'provider' method.
> >
> > When interacting with frameworks like Spring this does not give a lot of
> > flexibility. I described the problem statement and some ideas which could
> > be considered for evolving the services support in the module system in
> > this blog post:
> >
> >
> https://devcreativity.wordpress.com/2019/03/02/java-modules-wish-list-provide-services-using-lambda-functions-and-more/
> >
> >
> > I would appreciate if some of the oracle contributors that worked on the
> > module system could read the post and provide me and the community with
> > some feedback if such a change could be a good idea?
> >
> > Thanks in advance
> >
> > Tom
> >
>