code: public Unmarshaller getUnmarshaller(boolean reuse)
      throws JAXBException {
      if (!reuse || unmarshaller == null) {
        unmarshaller = context.createUnmarshaller();
      }
      return unmarshaller;
    }
docs: Returns the unmarshaller that converts a tree data structure
  from XML to Java objects.
  @param reuse	whether to reuse an existing unmarshaller
  @return	the unmarshaller for the JAXB context
  @throws JAXBException if unmarshaller initialization fails