public interface BookRepository extends CrudRepository<Book, Integer> {

    @Query("select a from Book a where  (a.title=:title or :title is null) AND (a.author=:author or :author is null) AND (a.category=:category or :category is null)")
    List<Book> findBooksByTitleAndAuthorAndCategory(@Param("title") String titleID,@Param("author") String authorID,@Param("category") String categoryID);
}