Currently, if logback.configurationFile is set to a filename which does not end in 'xml' or 'groovy', the logging system will fail to initialize, but will not emit any errors indicating the problem. Even with logback.debug enabled, the system is completely silent.

This is due to the absence of a catch-all 'else' in:

• ch.qos.logback.classic.util.ContextInitializer.configureByResource(...)
• ch.qos.logback.classic.turbo.ReconfigureOnChangeFilter.ReconfiguringThread.run()

At the very least, it would be easy to add an 'else' which logs an error about the filename.

On the other hand, a bit more involved solution would be to fallback to inspecting the contents of the file for something recognizable (like <?xml....)