Spring Bean 등록하는 4 가지 방법

4 가지 방법

1. xml - Bean 태그 이용

2. XML - componentScan 사용

3. Config파일을 통한 Bean 등록

4. Config의 ComponentScan을 활용한 Bean 등록

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1. xml - Bean 태그 이용

Resource 폴더에 application.xml 생성

application.xml

xml코드 복사
<?xml version="1.0" encoding="UTF-8"?>
<beans ...>
    <bean id="bookService" class="com.springstudy.springapplicationcontext.BookService">
        <property name="bookRepository" ref="bookRepository"/>
    </bean>
    <bean id="bookRepository" class="com.springstudy.springapplicationcontext.BookRepository"/>
</beans>

xml 파일을 로드하여 Application 실행

DemoApplication.java

java코드 복사
public class DemoApplication {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("application.xml");
        String[] beanDefinitionNames = context.getBeanDefinitionNames();
        System.out.println(Arrays.toString(beanDefinitionNames)); // bean name 출력
        BookService bookService = (BookService) context.getBean("bookService");
        System.out.println(bookService.bookRepository != null);
    }
}

2. XML - componentScan 사용

application.xml 수정

xml코드 복사
<?xml version="1.0" encoding="UTF-8"?>
<beans ...>
    <context:component-scan base-package="com.springstudy.springapplicationcontext"/>
</beans>

Bean Class에 어노테이션 작성

BookRepository.java

java코드 복사
@Repository
public class BookRepository {}

BookService.java

java코드 복사
@Service
public class BookService {
    @Autowired
    BookRepository bookRepository;

    public void setBookRepository(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }
}

3. Config파일을 통한 Bean 등록

ApplicationConfig.java 파일 생성 및 Bean 생성

ApplicationConfig.java

java코드 복사
@Configuration
public class ApplicationConfig {
   @Bean
   public BookRepository bookRepository() {
       return new BookRepository();
   }

   @Bean
   public BookService bookService() {
       BookService bookService = new BookService();
       bookService.setBookRepository(bookRepository());
       return bookService;
   }
}

ApplicationConfig를 로드하여 Application 실행

DemoApplication.java

java코드 복사
public class DemoApplication {
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(ApplicationConfig.class);
        String[] beanDefinitionNames = context.getBeanDefinitionNames();
        System.out.println(Arrays.toString(beanDefinitionNames)); // bean name 출력
        BookService bookService = (BookService) context.getBean("bookService");
        System.out.println(bookService.bookRepository != null);
    }
}

4. Config의 ComponentScan을 활용한 Bean 등록

ApplicationConfig.java

java코드 복사
@Configuration
@ComponentScan(basePackageClasses = DemoApplication.class)
public class ApplicationConfig {}

BookService.java

java코드 복사
@Service
public class BookService {
    @Autowired
    BookRepository bookRepository;

    public void setBookRepository(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }
}

DemoApplication.java

java코드 복사
@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}