Does the JAXB specification or any javadoc specifically say that
Unmarshaller (or Marshaller) objects are NOT thread-safe? I would
assume they are not, but I would like to confirm that. The spec
specifically talks about JAXBContext being thread-safe, but it doesn't
say whether Unmarshaller/Marshaller is or not. The javadoc doesn't say,
at least not that I've found.