docs: private File getFile(final ConfigurationSourceKey key) {
  		final String fileName = getFileName(key);
  		if (externalConfigPath != null) {
  			final File f = new File(externalConfigPath, fileName);
  			if (f.exists())
  				return f; // return overwritten configuration location
  		}
  		
  		// configuration-file was not overwritten, so read from class path
  		final ClassLoader myLoader = getClass().getClassLoader();
  		final URL url = myLoader.getResource(fileName);
  		
  		return url == null ? null : new File(url.getFile());
  	}