Aware

• Spring은 Aware라는 인터페이스를 제공한다.

• Aware 인터페이스를 구현하는 객체 인스턴스를 생성하면 특정 클래스에 대한 참조가 함께 제공된다.

• 특정 클래스에 대한 참조를 얻어 타입 캐스팅하거나 메서드를 호출하는 등 직접 여러 기능을 사용할 수 있다.

• 하지만 이 방식을 사용하면 스프링 컨텍스트와 강하게 결합된 코드가 되며 IoC를 따르지 않기 때문에 일반적으로는 사용하지 않는 것이 좋다고 한다.

• Aware를 구현하는 대신 Autowire하여 참조를 얻는 것이 더 권장된다. (생성자 주입 / Setter 주입 / 필드 주입)

• Aware의 종류는 아래와 같다.

Name	Injected Dependency	Explained in…​
ApplicationContextAware	Declaring ApplicationContext.	https://docs.spring.io/spring-framework/reference/core/beans/factory-nature.html#beans-factory-awarehttps://docs.spring.io/spring-framework/reference/core/beans/factory-nature.html#beans-factory-awarehttps://docs.spring.io/spring-framework/reference/core/beans/factory-nature.html#beans-factory-aware
ApplicationEventPublisherAware	Event publisher of the enclosing ApplicationContext.	https://docs.spring.io/spring-framework/reference/core/beans/context-introduction.htmlhttps://docs.spring.io/spring-framework/reference/core/beans/context-introduction.html
BeanClassLoaderAware	Class loader used to load the bean classes.	https://docs.spring.io/spring-framework/reference/core/beans/definition.html#beans-factory-class
BeanFactoryAware	Declaring BeanFactory.	https://docs.spring.io/spring-framework/reference/core/beans/beanfactory.htmlhttps://docs.spring.io/spring-framework/reference/core/beans/beanfactory.htmlhttps://docs.spring.io/spring-framework/reference/core/beans/beanfactory.html
BeanNameAware	Name of the declaring bean.	https://docs.spring.io/spring-framework/reference/core/beans/factory-nature.html#beans-factory-awarehttps://docs.spring.io/spring-framework/reference/core/beans/factory-nature.html#beans-factory-awarehttps://docs.spring.io/spring-framework/reference/core/beans/factory-nature.html#beans-factory-aware
LoadTimeWeaverAware	Defined weaver for processing class definition at load time.	https://docs.spring.io/spring-framework/reference/core/aop/using-aspectj.html#aop-aj-ltw
MessageSourceAware	Configured strategy for resolving messages (with support for parameterization and internationalization).	https://docs.spring.io/spring-framework/reference/core/beans/context-introduction.htmlhttps://docs.spring.io/spring-framework/reference/core/beans/context-introduction.html
NotificationPublisherAware	Spring JMX notification publisher.	https://docs.spring.io/spring-framework/reference/integration/jmx/notifications.html
ResourceLoaderAware	Configured loader for low-level access to resources.	https://docs.spring.io/spring-framework/reference/web/webflux-webclient/client-builder.html#webflux-client-builder-reactor-resources
ServletConfigAware	Current ServletConfig the container runs in. Valid only in a web-aware Spring ApplicationContext.	https://docs.spring.io/spring-framework/reference/web/webmvc.html#mvc
ServletContextAware	Current ServletContext the container runs in. Valid only in a web-aware Spring ApplicationContext.	https://docs.spring.io/spring-framework/reference/web/webmvc.html#mvc

사용 사례

• ApplicationEventPublisherAware를 사용하여 eventPublisher 참조를 MongoIndexedSessionRepository 객체에 주입할 수 있다. (3.2.1 버전 기준)

public class MongoIndexedSessionRepository
		implements FindByIndexNameSessionRepository<MongoSession>, ApplicationEventPublisherAware, InitializingBean {

	// ...

	private ApplicationEventPublisher eventPublisher;

	@Override
	public void setApplicationEventPublisher(ApplicationEventPublisher eventPublisher) {
		this.eventPublisher = eventPublisher;
	}

	// ...

}