why my springboot app cant see @Service annotation?

Question

My service class

package poklakni.library.service;
import java.util.List;
import java.util.function.Predicate;
import org.springframework.stereotype.Service;
import poklakni.library.entity.Book;

@Service
public interface BookService {

    //some crud methods
}

main class

package poklakni.library;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import poklakni.library.repository.BookRepository;
import poklakni.library.repository.PersonRepository;
import poklakni.library.service.BookService;
import poklakni.library.service.PersonService;

@SpringBootApplication
public class Application implements CommandLineRunner {

    @Autowired
    private BookService bookService;

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    public void run(String... args) throws Exception {

        //more code
    }
}

it says this

***************************
APPLICATION FAILED TO START
***************************
Description:

Field bookService in poklakni.library.Application required a bean of type 
'poklakni.library.service.BookService' that could not be found.

Action:

Consider defining a bean of type 'poklakni.library.service.BookService' in 
your configuration.

even if i add @ComponentScan ("poklakni.library") it doesnt work

i have also repo with @Repository annotation and it autowries it perfectly but service doesnt work what am I doing wrong? thank u for any advice

EDIT: there is also a implementation of service package poklakni.library.service;

import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;

import org.springframework.beans.factory.annotation.Autowired;

import poklakni.library.entity.Book;
import poklakni.library.repository.BookRepository;
import poklakni.library.repository.PersonRepository;

public class BookServiceImpl implements BookService {

    @Autowired
    private BookRepository bookRepo;

    //more code
}

Answer 1

BookService is an interface and cannot be instantiated. @Service should be put on the concrete class that implements BookService .

Answer 2

Please annotate you BookServiceImpl as @Service

@Service
public class BookServiceImpl implements BookService {

    @Autowired
    private BookRepository bookRepo;

    //more code
}