code: public static boolean isSunJAXB2Marshaller (@Nullable final Marshaller aMarshaller)
    {
      if (aMarshaller == null)
        return false;
      final String sClassName = aMarshaller.getClass ().getName ();
      return sClassName.equals (JAXB_EXTERNAL_CLASS_NAME);
    }
docs: Check if the passed Marshaller is a Sun JAXB v2 marshaller. Use this method
  to determined, whether the Sun specific methods may be invoked or not.
  
  @param aMarshaller
  The marshaller to be checked. May be <code>null</code>.
  @return <code>true</code> if the passed marshaller is not <code>null</code>
  and is of the Sun class.