Support scanning for classpath resources

[mpkorstanje]

Currently ReflectionUtils supports resolving class based selectors such as PackageSelector and ClasspathRootSelector. These can be resolved using findAllClassesInPackage and findAllClassesInClasspathRoot respectively.

Unfortunately there are no resource based equivalents to help resolve resources contained in a class path directory targeted by a ClasspathResourceSelector or ClasspathRootSelector e.g:

List<Resource> findAllResourcesInPackage(String basePackageName, ResourceFilter resourceFilter)

List<Resource> findAllResourcesInClasspathRoot(URI root, ResourceFilter resourceFilter) 

As this functionality is backed by the ClasspathScanner I believe it would be prudent to add this functionality prior to making the ClasspathScanner part of the public API as proposed in #3628. This would avoid breaking changes by adding more methods to an interface, or potential bug reports caused by a default implementation that always returns an empty collection of resources.

And I would be happy to provide a PR that facilitates this.

Deliverables

• Support for scanning class path resources through ReflectionUtils and ClasspathScanner.

[sbrannen]

We never implemented that, because we never needed to scan for resources (other than .class files).

What's the concrete use case you're thinking of -- scanning for Cucumber files or similar?

[mpkorstanje]

Yup. Cucumber uses .feature files which are typically located on the classpath.

The benefits would be two-fold

• Eventually replace Cucumbers classpath scanning with the JUnit Platform
• Benefit from implementations that support classpath scanning on Android.

[marcphilipp]

interface Resource {
	URI getUri();
	default InputStream getInputStream() throws IOException {
		return getUri().toURL().openStream();
	}
}

[marcphilipp]

Team decision: Let's add the two extra methods to ClasspathScanner and make them available via ReflectionSupport and ReflectionUtils.

As a follow-up task, we should add an addResourceContainerSelectorResolver() method to EngineDiscoveryRequestResolver.Builder analogous to addClassContainerSelectorResolver().

[marcphilipp]

@mpkorstanje A PR would be most welcome! 🙂

[mpkorstanje]

Cheers. I'll give it a shot.

As a follow-up task, we should add a addResourceContainerSelectorResolver() method to EngineDiscoveryRequestResolver.Builder analogous to addClassContainerSelectorResolver().

Oh that would be really nice!

[mpkorstanje]

I am still working on this, unfortunately due to circumstances it is going a bit slower than usual.

[sbrannen]

Thanks for letting us know, @mpkorstanje.

This is currently assigned to the 5.11 M2 milestone, so you've got a bit more time.