code: private String getPathExtension(HttpServletRequest request) {
  		String extension = UriUtils.extractFileExtension(request.getRequestURI());		
  		return extension != null ? "." + extension : "";
  	}
docs: /*
  Determines the path extension, if any.
  Returns the extension, including the period at the beginning, or an empty string if there is no extension.
  This makes it possible to append the returned value to a path even if there is no extension.