code: @Override
  	public Resource createRelative(String relativePath) throws MalformedURLException {
  		if (relativePath.startsWith("/")) {
  			relativePath = relativePath.substring(1);
  		}
  		return new UrlResource(new URL(this.url, relativePath));
  	}
docs: This implementation creates a UrlResource, applying the given path
  relative to the path of the underlying URL of this resource descriptor.
  @see java.net.URL#URL(java.net.URL, String)