code: public static ServiceRegistrarFactory load(final String source, final ClassLoader classLoader)
        throws ServiceRegistrarLoadingException {
      final ServiceLoader<ServiceRegistrarFactory> loader;
      try {
        loader = ServiceLoader.load(ServiceRegistrarFactory.class, classLoader);
      } catch (ServiceConfigurationError e) {
        throw new ServiceRegistrarLoadingException(
            "Failed to load service registrar from " + source, e);
      }
      final Iterator<ServiceRegistrarFactory> iterator = loader.iterator();
      if (iterator.hasNext()) {
        return iterator.next();
      } else {
        return null;
      }
    }
docs: Load a {@link ServiceRegistrarFactory} using a class loader.
  
  @param source      The source of the class loader.
  @param classLoader The class loader to load from.
  
  @return A {@link ServiceRegistrarFactory}, null if none could be found.
  
  @throws ServiceRegistrarLoadingException if loading failed.