@Override
 @Transactional(propagation = Propagation.REQUIRED)
 public BookEntity getBookByIsbn(String isbn)
     throws NoSuchEntityException, IllegalDatabaseStateException {
   return bookDao.getByIsbnNotNull(isbn);
 }
 @Override
 @Transactional(propagation = Propagation.REQUIRED)
 public Integer get(String isbn) throws NoSuchEntityException, IllegalDatabaseStateException {
   BookEntity book = bookDao.getByIsbnNotNull(isbn);
   return book.getId();
 }