crud

@Override
@Transactional
public void save(Book book) {
    entityManager.persist(book);
}

@Override
public Book get(Long id) {
    Book book = entityManager.find(Book.class, id);
    return book;
}

@Override
@Transactional
public void update(Book book) {
    //przekazany obiekt book musi mieć ustawiony klucz główny
    //na jego podstawie następuje "scalenie" danych
    entityManager.merge(book);
}

@Override
@Transactional
public void update2(Book book) {
    //wyszukujemy obiekt w bazie
    Book find = entityManager.find(Book.class, book.getId());
    if(find != null) {
        find.setTitle(book.getTitle());
        find.setIsbn(book.getIsbn());
        find.setAuthor(book.getAuthor());
    }
}

@Override
@Transactional
public void remove(Long bookId) {
    Book objToRemove = em.find(Book.class, bookId);
    em.remove(objToRemove);
    System.out.println(objToRemove.getId());
}