public void addBookCopy(int bookId, BookCopy copy) throws LibraryException {
   BookCopyConverter conv = new BookCopyConverter();
   BookCopyEntity newCopy = conv.fromBean(copy);
   newCopy.setBook(em.find(BookEntity.class, (long) bookId));
   em.persist(newCopy);
   // TODO test
 }
 public void addBook(Book book, BookCopy copy) throws LibraryException {
   BookConverter bookConv = new BookConverter();
   BookCopyConverter copyConv = new BookCopyConverter();
   BookEntity bookEntity = bookConv.fromBean(book);
   BookCopyEntity bookCopyEntity = copyConv.fromBean(copy);
   bookCopyEntity.setBorrowedBy(null);
   bookCopyEntity.setBook(bookEntity);
   em.persist(bookEntity);
   em.persist(bookCopyEntity);
 }