"exports" directive does not open module's resources for dependent modules

[Alan Bateman]

On 15/09/2017 13:14, Alexander Udalov wrote:
> It looks like exporting a package from a (non-open) module with an
> "exports" directive is not enough to ensure that
> Module.getResourceAsStream on that module would load resources from
> the module. Surprisingly, adding an "opens" directive for the same
> package to the module declaration allows resources to be found.
>
> I've put up a simple project to demonstrate this issue:
> https://github.com/udalov/jigsaw-resources-are-not-exported
>
> I'm wondering whether this is a bug or expected behavior?
Yes, this is expected behavior. The javadoc has all details. In your 
example, if kotlin.reflect is using Class.getResourceXXX or 
Module.getResourceAsStream to locate a non .class resource in module X 
then module X needs to open the package with the resource to at least 
kotlin.reflect.


> I would
> expect that exporting a package would also open it not only for uses
> of reflection, but for resource loading. I can't find anything related
> to resources in the JLS, but p.7.7 "Module Declarations" gives a clear
> impression that the "exports" directive gives a superset of
> functionality of the "opens" directive in this regard.
I think you need to re-read JLS 7.7.2. As `opens` doesn't grant any 
access at compile-time then you think of it as being a subset of 
`exports` in this phase.  On the other hand, `opens` grants access to 
the public classes/members and additionally reflective access to all 
members of all classes at run-time so you can think of it as a superset 
in this phase. The resource APIs just build on this.

-Alan