Should ClassLoader::getResouces return the same resource twice?

[Johannes Spangenberg]

Note that you are actually loading the JARs twice which means that you 
might have two versions of the same classses loaded, not only of the 
resources. Is this intentional? I still don't know what you want to 
achieve with your class loader and module layer.

Am 02.01.2021 um 21:06 schrieb Thiago Henrique Hupner:
> Yes, the parent loader locates two resources and it is used in the
> defineModulesWithOneLoader.
>
> So the behavior is the following:
> module-a.jar -> META-INF/web-fragment.xml
> module-b.jar -> META-INF/web-fragment.xml
>
> Creating a URLClassloader with these two jars and calling the getResources,
> it returns two URLs.
>
> If then I create a module for each jar, the contents of each module will be
> the same as the content
> found by the URLClassloader.
> Using that classloader as the parent in the defineModulesWithOneLoader
> gives the following behavior:
>
> Calling getResources with the loader created by the ModuleLayer,
> it will search the resources in all the modules of that layer (module.a and
> module.b),
> and then delegate to the parent (URLClassloader), which will find the same
> resources,
> thus, doubling the results.
>
> Now describing it make clear to me that is something not easy to fix,
> so by now, I worked around it by creating a ModuleReader that only
> find the ".class" files in the module and the other resources will be
> available by the parent,
> however, I don't know if this solution is the best.
>
>
> Em sáb., 2 de jan. de 2021 às 14:51, Alan Bateman <Alan.Bateman at oracle.com>
> escreveu:
>
>> On 02/01/2021 12:59, Thiago Henrique Hupner wrote:
>>> I guess a little context can make more things clear:
>>> The servlet spec requires that all jars from WEB-INF/lib
>>> be available to the same classloader.
>>> The resource, in particular, is "META-INF/web-fragment.xml"
>>> Each jar can contain its own. So, using getResources make sense
>>> in order of parsing each. However, what is happening is if I have two
>> JARs
>>> each with its own META-INF/web-fragment.xml, using the ModuleReader
>>> it is returning four resources, so it parses more than it should and
>>> it fails
>>> to parse the same resource twice.
>>>
>> Which parent class loader are you specifying to
>> defineModulesWithOneLoader? It it possible that it locates the resource
>> in the two JAR files?
>>
>> -Alan
>>