The Util interface should not be preferred. Implementations of Util can be
preferred but not Util itself.
Services need a common api that all implementations and clients can use to
interract, even if this is a kind of codebase service.
Modifying an interface is generally considered bad practise but now Java 8
makes it possible to add default methods for added functionality, that line
blurs somewhat. What can you do if an earlier interface is loaded by a parent
ClassLoader and you need a later version, make it preferred?
My thoughts are that interfaces should never be preferred and all classes
defined in their methods shouldn't be preferred either.
It would be relatively easy to write a new implementation that ensures that
interfaces are loaded into their own ProtectionDomain in a parent ClassLoader.
But that would be confusing as dynamic policy grants are made to ClassLoader's
not ProtectionDomains.
But using ProtectionDomains in this manner, preserves security, ensures maximum
visibility and avoids codebase annotation loss, if we ask the ProtectionDomain
for the annotation, instead of the ClassLoader. But this is not how we do
things presently.
Cheers,
Peter.
----- Original message -----
> But it will also be loaded by WrapperProxy ClassLoader, since it is
> preferred there. So it will end up with ClassCastException, right?
>
> Regards,
> Michal
>
> If Util is installed locally, it will only be loaded by the application
> ClassLoader, since it isn't preferred.
>
> Peter.
>
> ----- Original message -----
> > Folks,
> > while woking on the River-436 patch proposal I've came across the
> > scenario that I am not sure how to handle:
> >
> > Utility service:
> > //inteface is NOT preferred
> > interface Util {...}
> > //class IS preferred
> > class UtilProxy implements Util {}
> >
> > Wrapper service:
> > //NOT preferred
> > interface Wrapper {}
> > //preferred
> > class WrapperProxy implements Serializable{
> > //initialized with Util impl from a lookup service
> > private Util util;
> > }
> >
> > Wrapper service codebase includes Util interface but it is _preferred_.
> >
> > Would deserialization of WrapperProxy end with ClassCastException?
> > From what I understand UtilProxy is annotated with its codebase. When
> > deserializing UtilProxy a ClassLoader is going to be created with
> > parent set to TCCL. It means Util interface is going to be loaded
> > twice by two ClassLoaders - one for WrapperProxy codebase and another
> > for UtilProxy codebase.
> >
> > Am I correct?
> > And if so: is it desired behavior?
> >
> > Regards,
> >
> > --
> > Michał Kłeczek
> > XPro Quality Matters
> > http://www.xpro.biz
> >
