private TimeTracker loadTimeTracker() throws JAXBException {
        JAXBContext jaxbContext = JAXBContext.newInstance(TimeTracker.class);
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        Object object = unmarshaller.unmarshal(openInputStream());
        if (object instanceof TimeTracker) {
            return (TimeTracker) object;
        } else {
            throw new TimeTrackerException("Can't find TimeTracker element in xml.");
        }
    }