Layers and NoClassDefFoundError

[Nicolai Parlog]

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 Hi,

I am currently experimenting with layers and running into
NoClassDefFoundErrors. Maybe someone on the list can help me out.

I create one layer on top of the boot layer and a second one on top of
the first. The second contains code that references a class from the
first. As I understand SOTMS[1] this should work. But it doesn't and
when I execute code in the second layer I get a NoClassDefFoundError.


In a little more detail...

I verified that all classes that are accessed across module boundaries
are exported. The individual modules correctly state their
dependencies on other modules.

This is how I create both layers (inspired by the Javadoc on
java.lang.reflect.Layer):

		ModuleFinder finder = ModuleFinder.of(modulePaths);
		Configuration configuration =
			Configuration.resolve(
				ModuleFinder.empty(),
				parentLayer,
				finder,
				moduleNames);
		ClassLoader loader =
			new ModuleClassLoader(configuration);
		return Layer.create(
			configuration,
			moduleName -> loader);

For the first layer 'parentLayer' is 'Layer.boot()', for the second
it's the first.

Then I add a read edge from the module that runs all this to the one
in the second layer that contains the code I actually want to execute.
Finally I access the code I actually want to run (in the second layer)
and invoke it. I then get a NoClassDefFoundError for a class that is
present in the first layer.

I tried adapting the 'parentLayer' to be used as the 'beforeFinder' in
'Configuration.resolve' instead of 'ModuleFinder.empty()' but that
gave me a 'LayerInstantiationException' ("Module java.base is already
defined").

Where did I get it wrong?

 Thanks in advance
 Nicolai


[1] last paragraph:
	http://openjdk.java.net/projects/jigsaw/spec/sotms/#layers



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