Is Spring annotation @Controller same as @Service?

Question

Is Spring annotation @Controller same as @Service?

I have idea about @Controller which can be used for URL mapping and invoking business logic.

while @Service used to annotate service class which contains business logic.

Can I use @Controller instead of @Service to annotate Service class?

Answer 1

No, they are pretty different from each other.

Both are different specializations of @Component annotation (in practice, they're two different implementations of the same interface) so both can be discovered by the classpath scanning (if you declare it in your XML configuration)

@Service annotation is used in your service layer and annotates classes that perform service tasks, often you don't use it but in many case you use this annotation to represent a best practice. For example, you could directly call a DAO class to persist an object to your database but this is horrible. It is pretty good to call a service class that calls a DAO. This is a good thing to perform the separation of concerns pattern.

@Controller annotation is an annotation used in Spring MVC framework (the component of Spring Framework used to implement Web Application). 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. The dispatcher scans such annotated classes for mapped methods and detects @RequestMapping annotations.

So looking at the Spring MVC architecture you have a DispatcherServlet class (that you declare in your XML configuration) that represent a front controller that dispatch all the HTTP Request towards the appropriate controller classes (annotated by @Controller). This class perform the business logic (and can call the services) by its method. These classes (or its methods) are typically annotated also with @RequestMapping annotation that specify what HTTP Request is handled by the controller and by its method.

For example:

@Controller @RequestMapping("/appointments") public class AppointmentsController {      private final AppointmentBook appointmentBook;      @Autowired     public AppointmentsController(AppointmentBook appointmentBook) {         this.appointmentBook = appointmentBook;     }      @RequestMapping(method = RequestMethod.GET)     public Map<String, Appointment> get() {         return appointmentBook.getAppointmentsForToday();     } 

This class is a controller.

This class handles all the HTTP Request toward "/appointments" "folder" and in particular the get method is the method called to handle all the GET HTTP Request toward the folder "/appointments".

I hope that now it is more clear for you.

Answer 2

If you look at the definitions of @Controller, @Service annotations, then you'll find that these are special type of @Component annotation.

@Component public @interface Service {     …. } 

 

@Component public @interface Controller {     … } 

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So what's the difference?

@Controller

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?

You 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. You can only use @RequestMapping on @Controller annotated classes.

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@Service

@Services hold business logic and call method in repository layer.

What’s special about @Service?

Apart from the fact that it is used to indicate that it's holding the business logic, there’s no noticeable specialty that this annotation provides, but who knows, spring may add some additional exceptional in future.

Linked answer: What's the difference between @Component, @Repository & @Service annotations in Spring?