About Spring @Component, @Repository, @Service and @Controller Annotations.

Spring @Component, @Service, @Repository and @Controller annotations are used for automatic bean detection using classpath scan in Spring framework.
These four  annotations are same logically.

Differences between @Component, @Repository, @Controller and @Service:

@Component

 This is a general-purpose stereotype annotation(auto scan) indicating that the class is a spring component. @Component annotation picks them up and registers their following classes as beans, just as if they were annotated with @Component.

@Repository

This is special type of @Component annotation. 

This is to indicate that the class defines a data repository. 

@Controller

This is special type of @Component annotation.

The @Controller annotation indicates that a particular class serves the role of a controller. The @Controller annotation acts as a stereotype for the annotated class, indicating its role. 

What’s special about @Controller?
We cannot switch this annotation with any other like @Service or @Repository, even though they look same. The dispatcher scans the classes annotated with @Controller and detects @RequestMapping annotations within them. We can only use @RequestMapping on @Controller annotated classes.
  
@Service
This is special type of @Component annotation. 
@Services hold business logic and call method in repository layer.

Summary:

| Annotation | Meaning                                             |
+------------+-----------------------------------------------------+
| @Component | generic stereotype for any Spring-managed component |
| @Repository| stereotype for persistence layer                    |
| @Service   | stereotype for service layer                        |
| @Controller| stereotype for presentation layer (spring-mvc)      |