Spring Annotations: @Component, @Repository, @Service

Spring's @Component, @Repository, @Service, @Controller Annotations: A Concise Guide

Spring's stereotype annotations (@Component, @Repository, @Service, @Controller) mark classes for auto-detection and dependency injection. They essentially do the same thing: register a bean in the Spring context. However, they provide semantic meaning:

• @Component: A general-purpose stereotype for any Spring-managed component. Use this as a base or when the component doesn't fit the others.

• @Repository: Specifically for data access objects (DAOs). Provides exception translation (e.g., converting SQLExceptions to Spring's DataAccessException).

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    // ...
}

• @Service: For business logic services. Clearly distinguishes business logic from other components.

@Service
public class UserService {
    // ... business logic using UserRepository ...
}

• @Controller: For handling web requests (typically used with Spring MVC).

@Controller
public class UserController {
    // ... handles HTTP requests ...
}

Choosing the right annotation improves code readability and maintainability. While interchangeable in basic scenarios, using specific annotations enhances understanding and facilitates future refactoring. Spring's auto-detection mechanism handles the rest.