How to let an automatic module find its own resources in Java 9?

Question

I am trying to get my application to run with Java 9, but unfortunately one of the plain jar dependencies, when it tries to load a resource using classLoader.getResource(name), gets a null instead.

This, of course, works in Java 8.

I declared a dependency on the module in question using the module file, referring to the name of the module by its jar name (awful), and added the jar as-is (no customization for Java 9) using the --module-path option.

Here is my approximate module file declaration:

module my.mod {
    requires ivy; // the file is called ivy-2.4.0.jar
}

And I run with this command:

java --module-path my-mod.jar:ivy-2.4.0.jar -m my.mod

When I run the application, it works fine if the library doesn't try to load that resource... but if it does, it gets a NullPointerException at the line it tries to use the resource.

I can see the resource is present in the correct path in the jar file.

I've tried running my application both as a jar (shown above) and just with the class files:

java --module-path modules-dir:ivy-2.4.0.jar -m my.module/my.Main

In the latter case, the error is different, but related: Ivy can't even find a properties file it tries to load from its own jar!

Is there any workaround, is this a known bug, or am I doing something wrong?

Answer 1

Try to add an 'opens' declaration to the automatic module 'ivy'. That allows access to it's resources:

java --add-opens ivy/<dot.separated.path.to.resources>=ALL-UNNAMED --module-path my-mod.jar:ivy-2.4.0.jar -m my.mod