protected <T> T unmarshal(Class<T> klass, String fileName) throws JAXBException
{
    JAXBContext context = JAXBContext.newInstance(klass.getPackage().getName());
    Unmarshaller unmarshaller = context.createUnmarshaller();
    InputStream stream = this.getClass().getResourceAsStream(fileName);
    JAXBElement jaxbElement = (JAXBElement) unmarshaller.unmarshal(stream);
    return (T) jaxbElement.getValue();
}

How to do the reverse:

// See http://stackoverflow.com/questions/2472155/i-want-to-convert-an-output-stream-into-string-object
public <T> String marshal(Class <T> klass, T object) throws JAXBException
{
  StringWriter writer = new StringWriter();
  JAXBContext context = JAXBContext.newInstance(klass);
  Marshaller marshaller = context.createMarshaller();
  marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
  marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
  JAXBElement jaxbElement = new JAXBElement<T>(new QName("","rootTag"), klass, object);
  marshaller.marshal(jaxbElement, writer);
  return writer.toString();
}