code: protected XMLEvent readStartTag(XMLEventReader reader, QName tagName)
              throws XMLStreamException, JournalException {
          XMLEvent event = reader.nextTag();
          if (!isStartTagEvent(event, tagName)) {
              throw getNotStartTagException(tagName, event);
          }
          return event;
      }
docs: Read the next event and complain if it is not the Start Tag that we
  expected.