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
| Annotation | Meaning |
|---|---|
@Component | the generic stereotype for any Spring-managed component |
@Repository | the stereotype for the persistence layer |
@Service | the stereotype for the service layer |
@Controller | the 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
DataAccessExceptiontranslation when used in conjunction with aPersistenceExceptionTranslationPostProcessor. 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.