@Autowired

@Component
public class OrderServiceImpl implements OrderService {
 	private final MemberRepository memberRepository;
 	private final DiscountPolicy discountPolicy; 
    
 @Autowired
 public OrderServiceImpl(MemberRepository memberRepository, DiscountPolicy discountPolicy) {
	 	this.memberRepository = memberRepository;
 		this.discountPolicy = discountPolicy;
 }
}

[코드1. 생성자 주입]

//테스트에서 사용 예시
@SpringBootTest
class PostServiceTest {

    @Autowired
    private BoardService boardService;
}

[코드2. 빈으로 등록된 객체를 의존성 주입할 때 사용]