为什么我的springboot应用程序看不到@Service批注？

Question

我的服务等级

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
}

主班

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
    }
}

它说

***************************
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.

即使我添加@ComponentScan（“ poklakni.library”），它也不起作用

我也使用@Repository批注进行回购，它可以完美地自动工作，但是服务不起作用我在做什么错呢？ 谢谢你的任何建议

编辑：还有一个服务包poklakni.library.service的实现；

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是一个接口，无法实例化。 @Service应该放在实现BookService的具体类上。

Answer 2

请用@Service注释BookServiceImpl

@Service
public class BookServiceImpl implements BookService {

    @Autowired
    private BookRepository bookRepo;

    //more code
}