BookQuery.java

@Controller
@AllArgsConstructor
public class BookQuery{

    private final BookRepository bookRepository;

    @QueryMapping
    public Iterable<Book> allBook(){
        return bookRepository.findAll();
    }

    @QueryMapping
    public Book getBookByTitle(@Argument("filter") BookInput bookInput){
        return bookRepository.findBookByTitle(bookInput.getTitle());
    }
}