Other class-level annotations may be considered as identifying * a component as well, typically a special kind of component: * e.g. the {@link Repository @Repository} annotation or AspectJ's * {@link org.aspectj.lang.annotation.Aspect @Aspect} annotation. * * @author Mark Fisher * @since 2.5 * @see Repository * @see Service * @see Controller * @see org.springframework.context.annotation.ClassPathBeanDefinitionScanner */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Indexed public @interface Component { /** * 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 (or empty String otherwise) */ String value() default ""; } ``` ### @Bean과 @Component는 어떤 차이가 있는가? * @Component는 클래스 상단에 적으며 그 default로 클래스 이름이 bean의 이름이 된다. 또한 spring에서 자동으로 찾고(@ComponentScan 사용) 관리해주는 bean이다. * @Bean은 @Configuration으로 선언된 클래스 내에 있는 메소드를 정의할 때 사용한다. 이 메소드가 반환하는 객체가 bean이 되며 default로 메소드 이름이 bean의 이름이 된다. ## @Controller Dispatcher Sevlet에서 제공되며 여기서 @RequestMapping 어노테이션을 사용하여 클라이언트 요청을 특정 컨트롤러에 전달할 수 있게 해준다. ```java /** * Indicates that an annotated class is a "Controller" (e.g. a web controller). * *
This annotation serves as a specialization of {@link Component @Component}, * allowing for implementation classes to be autodetected through classpath scanning. * It is typically used in combination with annotated handler methods based on the * {@link org.springframework.web.bind.annotation.RequestMapping} annotation. * * @author Arjen Poutsma * @author Juergen Hoeller * @since 2.5 * @see Component * @see org.springframework.web.bind.annotation.RequestMapping * @see org.springframework.context.annotation.ClassPathBeanDefinitionScanner */ @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Component public @interface Controller { ... } ``` ### @RestController와 @Controller의 차이는? @RestController는 Spring 3.0 에서 추가된 어노테이션으로 RESTful web service를 제공하기 위해 @Controller를 확장한 개념이다. 기능적인 측면에서 보았을 땐 @Controller에 @ResponseBody 어노테이션을 추가된 기능이라고 보면 된다. @ResponseBody 어노테이션의 기능은 결과값을 View를 통해서 출력되지 않고 HTTP Response Body에 직접 쓰여지게 되며 이때 리턴되는 데이터 타입에 따라 MessageConverter 에서 변환이 이뤄진 후 쓰여지게 된다. ```java * Types that carry this annotation are treated as controllers where * {@link RequestMapping @RequestMapping} methods assume * {@link ResponseBody @ResponseBody} semantics by default. * *
NOTE: {@code @RestController} is processed if an appropriate * {@code HandlerMapping}-{@code HandlerAdapter} pair is configured such as the * {@code RequestMappingHandlerMapping}-{@code RequestMappingHandlerAdapter} * pair which are the default in the MVC Java config and the MVC namespace. * * @author Rossen Stoyanchev * @author Sam Brannen * @since 4.0 */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Controller @ResponseBody public @interface RestController { ... } ``` ## @Service Service annotation은 단순히 서비스 레이어에서 사용하는 bean이라는 것을 구분하기 위한 용도로 정의한다. 그러므로 @Component로 대체해도 무방하지만 권장하지는 않는다. ```java /** * Indicates that an annotated class is a "Service", originally defined by Domain-Driven * Design (Evans, 2003) as "an operation offered as an interface that stands alone in the * model, with no encapsulated state." * *
May also indicate that a class is a "Business Service Facade" (in the Core J2EE * patterns sense), or something similar. This annotation is a general-purpose stereotype * and individual teams may narrow their semantics and use as appropriate. * *
This annotation serves as a specialization of {@link Component @Component}, * allowing for implementation classes to be autodetected through classpath scanning. * * @author Juergen Hoeller * @since 2.5 * @see Component * @see Repository */ @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Component public @interface Service { ... } ``` ## @Repository 검사 되지 않은 예외(DAO 메소드에서 발생)를 Spring DataAccessException으로 변환 할 수 있게 해준다. ```java * *
A class thus annotated is eligible for Spring * {@link org.springframework.dao.DataAccessException DataAccessException} translation * when used in conjunction with a {@link * org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor * PersistenceExceptionTranslationPostProcessor}. The annotated class is also clarified as * to its role in the overall application architecture for the purpose of tooling, * aspects, etc. * *
As of Spring 2.5, this annotation also serves as a specialization of * {@link Component @Component}, allowing for implementation classes to be autodetected * through classpath scanning. * * @author Rod Johnson * @author Juergen Hoeller * @since 2.0 * @see Component * @see Service * @see org.springframework.dao.DataAccessException * @see org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor */ @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Component public @interface Repository { ``` ## @Configuration 한 개 이상의 @Bean 어노테이션으로 정의한 bean 들을 생성하려 할 때 클래스에 정의하는 어노테이션이다. ```java *