Resource loading of message bundles always needs classpath prefix

[philwebb]

The fix for spring-projects/spring-hateoas#1075 shows that the ResourceLoader used by devtools seems to require the classpath: prefix.

This issue was raised by @odrotbohm on Slack:

In my local test, I immediately run into DefaultResourceLoader, whereas the Boot project ends up in GenericApplicationContext, which then delegates to org.springframework.boot.devtools.restart.ClassLoaderFilesResourcePatternResolver which in turn delegates to a org.springframework.web.context.support.ServletContextResourcePatternResolver.

It's a bit tricky [to reproduce]. The original request is this one: spring-projects/spring-hateoas#1075. I managed to see the resources not being loaded when putting a breakpoint at ReloadableResourceBundleMessageSource.refreshProperties(…). The Resource lookup returns the ServletContextResource when you initiate the request like Kai describes.
My local test for this has been introduced here: spring-projects/spring-hateoas@507f7de. You can also see that I tweaked the setup to explicitly include the classpath: prefix for that. However, the test actually succeeds without that addition as well.