What’s the difference between @Controller, @Component, @Repository & @Service annotations in Spring?


Spring has many annotations used for different purposes. There are some key class annotations like @RestController @Controller, @Component, @Repository & @Service which do a similar job but actually have some differences between them and all extends @Component.

In General, you can think of these annotations used for the different domains in domain-driven design as given below

AnnotationMeaning
@Componentthe generic stereotype for any Spring-managed component
@Repositorythe stereotype for the persistence layer
@Servicethe stereotype for the service layer
@Controllerthe stereotype for the presentation layer (spring-mvc)

Here is the relationship between them

@Component

Indicates that an annotated class is a “component”. Such classes are considered candidates for auto-detection when using annotation-based configuration and classpath scanning.
Other class-level annotations may be considered as identifying a component as well, typically a special kind of component: e.g. the @Repository annotation or AspectJ’s @Aspect annotation.

@Repository

Indicates that an annotated class is a “Repository”, originally defined by Domain-Driven Design (Evans, 2003) as “a mechanism for encapsulating storage, retrieval, and search behavior which emulates a collection of objects”..

A class thus annotated is eligible for Spring DataAccessException translation when used in conjunction with a PersistenceExceptionTranslationPostProcessor. The annotated class is also clarified as to its role in the overall application architecture for the purpose of tooling, aspects, etc

@Service

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.”

This annotation serves as a specialization of @Component, allowing for implementation classes to be autodetected through classpath scanning.

@Controller

Indicates that an annotated class is a “Controller” (e.g. a web controller).
This annotation serves as a specialization of @Component, allowing for implementation classes to be autodetected through classpath scanning. It is typically used in combination with annotated handler methods based on the RequestMapping annotation.


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