Spring Framework Core (2) - Spring Bean 주입 방법 및 예시

스프링 빈

• 스프링 빈은 이름, 타입, 객체로 구성
• @Configuration + @Bean
  • 프레임워크를 설정할 때
  • 애플리케이션을 설정할 때
  • 애플리케이션 전체에서 공통으로 사용할 때
• @ConponentScan + Stereotype Annotation
  • 비즈니스 로직을 처리할 때

예시로 들어가기전 file tree

KaKao & Member는 NotificationService를 상속받고 있다.

Spring Bean 주입 - @Bean + @Configuration : 01

• 메서드의 파라미터 전달

@Configuration
public class JavaConfig {

    @Bean
    public MemberRepository memberRepository() {
        return new MemberRepository();
    }

    @Bean
    public NotificationService notificationService(MemberRepository memberRepository) {
        return new NotificationService(memberRepository);
    }

}

Spring Bean 주입 - @Bean + @Configuration : 02

• 메서드 호출

@Configuration
public class JavaConfig {

    @Bean
    public MemberRepository memberRepository() {
        return new MemberRepository();
    }

    // with method parameter
    @Bean
    public NotificationService notificationService() {
        return new NotificationService(memberRepository());
    }}
}

Spring Bean 주입 - @Stereotype Annotations

3가지 방법이 존재한다.

• Field Injection
• Setter Injection
• Constructor Injection

Spring Bean 주입 - Field Injection

• @Autowired 와 @Qualifier 를 활용하여 Injection한다.

// scan
@ComponentScan(basePackages ="com.nhndooray.edu.spring_core.service")
public class Config {

}

// Bean 주입
@Component("kakaoService")
public class KakaoServiceImpl implements NotificationService {
    @Override

@Component("smsService")
public class SmsServiceImpl implements NotificationService {
    @Override

// 활용
@Autowired
private NotificationService smsService;

@Autowired
@Qualifier("kakaoService")
private NotificationService kakaoService;

Spring Bean 주입 - Setter Injection

• 클래스 방식으로 주입

private NotificationService smsService;
private NotificationService kakaoService;

public void smsService(SmsService smsService){
	this.smsService = smsService;
}

@Autowired
@Qualifier("kakaoService")
public void setKakaoService(NotificationService kakaoService) {
    this.kakaoService = kakaoService;
}

Spring Bean 주입 - Constructor Injection

• 생성자에서 주입

private final NotificationService smsService;
    private final NotificationService kakaoService;

    public MemberServiceImpl(NotificationService smsService,
                             NotificationService kakaoService) {
        this.smsService = smsService;
        this.kakaoService = kakaoService;
    }