code: public void respondUsing(final RespondWithBlob callback) throws IOException {
      RespondWithData dataCallback = new RespondWithData() {
        @Override
        public Data onInterest(Name prefix, Interest interest) throws Exception {
          Data data = new Data(interest.getName());
          Blob content = callback.onInterest(prefix, interest);
          data.setContent(content);
          return data;
        }
      };
      respondUsing(dataCallback);
    }
docs: Convenience method for responding to an {@link Interest} by returning the
  {@link Blob} content only; when an Interest arrives, this method wraps the
  returned Blob with a {@link Data} using the exact {@link Name} of the
  incoming Interest.
  
  @param callback the callback function to retrieve content when an
  {@link Interest} arrives
  @throws java.io.IOException if the server fails to register a prefix