IoC 컨테이너와 빈(2) - 컴포넌트 스캔

@Component

@controller

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Controller {

	/**
	 * The value may indicate a suggestion for a logical component name,
	 * to be turned into a Spring bean in case of an autodetected component.
	 * @return the suggested component name, if any
	 */
	String value() default "";

}

 

@Service

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Service {

	/**
	 * The value may indicate a suggestion for a logical component name,
	 * to be turned into a Spring bean in case of an autodetected component.
	 * @return the suggested component name, if any
	 */
	String value() default "";

}

 

@Repository

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Repository {

	/**
	 * The value may indicate a suggestion for a logical component name,
	 * to be turned into a Spring bean in case of an autodetected component.
	 * @return the suggested component name, if any
	 */
	String value() default "";

}

 

@Bean

@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Bean {

	/**
	 * The name of this bean, or if plural, aliases for this bean. If left unspecified
	 * the name of the bean is the name of the annotated method. If specified, the method
	 * name is ignored.
	 */
	String[] name() default {};

	/**
	 * Are dependencies to be injected via autowiring?
	 */
	Autowire autowire() default Autowire.NO;

	/**
	 * The optional name of a method to call on the bean instance during initialization.
	 * Not commonly used, given that the method may be called programmatically directly
	 * within the body of a Bean-annotated method. Default value is {@code ""}, indicating
	 * that no init method should be called.
	 */
	String initMethod() default "";

	/**
	 * The optional name of a method to call on the bean instance upon closing the
	 * application context, for example a {@code close()} method on a JDBC {@code
	 * DataSource} implementation, or a Hibernate {@code SessionFactory} object.
	 * The method must have no arguments but may throw any exception.
	 * <p>As a convenience to the user, the container will attempt to infer a destroy
	 * method against object returned from the {@code @Bean} method. For example, given a
	 * {@code @Bean} method returning an Apache Commons DBCP {@code BasicDataSource}, the
	 * container will notice the {@code close()} method available on that object and
	 * automatically register it as the {@code destroyMethod}. This 'destroy method
	 * inference' is currently limited to detecting only public, no-arg methods named
	 * 'close'. The method may be declared at any level of the inheritance hierarchy, and
	 * will be detected regardless of the return type of the {@code @Bean} method, i.e.
	 * detection occurs reflectively against the bean instance itself at creation time.
	 * <p>To disable destroy method inference for a particular {@code @Bean}, specify an
	 * empty string as the value, e.g. {@code @Bean(destroyMethod="")}.
	 * <p>Note: Only invoked on beans whose lifecycle is under the full control of the
	 * factory, which is always the case for singletons but not guaranteed 
	 * for any other scope.
	 * @see org.springframework.context.ConfigurableApplicationContext#close()
	 */
	String destroyMethod() default AbstractBeanDefinition.INFER_METHOD;

}

@Component와 @Bean의 차이

• @Bean 어노테이션의 경우 개발자가 직접 제어가 불가능한 외부라이브러리 등을 Bean으로 만들때 사용한다.
• @Component는 개발자가 직접 작성한 class를 Bean으로 등록하기위해서 사용한다.
  
• @Service, @Controller, @Repository은 실제 동작하는건 같지만 기능별로 분류해 놓았다.

 

@Component Scan이란

<context:component-scan base-package="kr.co.styudy" />

• Spring에서는 XML에 위의 코드를 작성함으로써 @Component가 해당 패키지를 기본으로하여 어노테이션을 읽어 Bean으로 등록해주는 역할을 한다.
• 실제 스캐닝은 ConfigurationclassPostProcessor라는 BeanFactoryPostProcessor에 의해 처리가 된다.
• excludeFilters, includeFilters 등을 사용하게 되면 Bean으로 등록하지 못하게 한다.

 

평션을 사용한 빈 등록

public static void main(String[] args) { 
	new SpringApplicationBuilder() 
		.sources(Demospring51Application.class)
        .initializers((ApplicationContextInitializer<GenericApplicationContext>) 
        applicationContext -> { 
			applicationContext.registerBean(MyBean.class); }) 
        .run(args); 
}