2009/3/19 Stephen Connolly <stephen.alan.conno...@gmail.com>
> 2009/3/19 sebb <seb...@gmail.com>
>
> > On 19/03/2009, Rusty Wright <rusty.wri...@gmail.com> wrote:
> > > Do the imports only have an effect at compile time? For example, if
> you
> > > have
> > >
> > > package impl.zzz;
> > >
> > > import api.yyy.Yyy;
> > >
> > > public class Xyz implements Yyy {
> > > }
> > >
> > > When you run the app the jvm won't need to have the yyy.Yyy class
> > > available?
> >
> > Yes, that's what I wrote.
> >
> > At runtime:
> > - annotation jars are not needed
>
> Only if they have a retention of compile.... if they are retained at
> runtime
> you'll need them on the classpath
>
another thing to note about runtime retained annotations is that you can
actually use the annotated class without having the annotation classes on
the runtime classpath - however when you query the class using reflection
you won't be able to see the missing annotations, because the JVM filters
them out as part of the classloading process
this means you can annotate classes with Spring+Guice+EJB annotations
and you'll only need all of these framework jars when compiling the source
when it comes to deployment you just need to pick the framework that you
intend to use, which 'activates' the necessary annotations - the others are
still in the class-file waiting for when you deploy it to another framework
HTH
>
> > - code jars are needed, but they may be different from the ones used to
> > compile.
> >
> > Can I get back to my original question, which is:
> >
> > How does one express a dependency on a jar which is only needed at
> > compile time, such that the dependency is not propagated?
> >
>
> scope provided will do what you need afaik
>
>
> >
> > > Even if that's true it seems dubious to me because it seems to me that
> > that
> > > means your code is always referring to the concrete class Xyz when it
> > should
> > > be using the interface Yyy. For example, how could you do
> > >
> > > Yyy y = new Xyz();
> > >
> > > Would that run without the interface class on the classpath?
> > >
> > >
> > > sebb wrote:
> > >
> > > >
> > > > On 18/03/2009, sebb <seb...@gmail.com> wrote:
> > > >
> > > > > AIUI, "compile" scope means compile, test and run, and generates a
> > > > > transitive dependency.
> > > > >
> > > > > There are some dependencies that are compile-time only, for
> example
> > > > > annotations, and Java specification jars - i.e. API-only jars that
> > > > > have no implementation.
> > > > >
> > > > > What is the best way to define such a dependency?
> > > > >
> > > > > The Maven site suggests using "provided", but this does not solve
> > the
> > > problem.
> > > > >
> > > > > Maybe there should be a"compile-only" scope?
> > > > >
> > > > >
> > > >
> > > > Note that in the case of annotation jars, these are not needed at
> > > run-time.
> > > >
> > > > In the case of API-only jars, at run-time one would use a different
> > > > jar which has the full implementation. This is useful for public
> specs
> > > > which might not have open source implementations. The API-only jars
> > > > allow one to compile.
> > > >
> > > >
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>
--
Cheers, Stuart
