code: public final FilterFactoryReference addingService(ServiceReference<FilterFactory> reference) {
          FilterFactory filterFactory = bundleContext.getService(reference);
          if (filterFactory != null) {
              FilterFactoryReference factoryReference = new FilterFactoryReference(filterFactory);
              LOGGER.debug("added FilterFactory {} for application {}", filterFactory.getClass().getName(),
                  applicationName);
              return factoryReference;
          }
          return null;
      }
docs: {@inheritDoc}