What will happen if we interchange @service and @repository annotation in the spring MVC

According to documentaion @Repository,@Service,@Controller are all synonyms. They all just specializations of @Component annotation. So, generally, they can be used one istead of other. But ... you should not do this.

First reason: any of this annotations make clear the role of your component in the application. Shows - is this component belongs to controller, service, or data layer.

Second reason: some of this annotations processed differently by different Spring modules. For example, Spring Data JPA will process @Repository, and will try to replace with implementation any interface marked by this annotaion. Spring also will apply automatic exception translation to such classes. Another example, Spring Web MVC process @Controller, and use classes marked with it in URL mappings.

Actually, in future versions, some modules of Spring could process @Service in particular way. Not as simple @Component. That's why documentation advises:

It is also possible that @Repository, @Service, and @Controller may carry additional semantics in future releases of the Spring Framework. Thus, if you are choosing between using @Component or @Service for your service layer, @Service is clearly the better choice.

It depends on what you use for the remainder of the framework. In theory nothing changes as the @Service and @Repository annotations are basically @Component annotations. The same could be said for @Controller or @Endpoint (for Spring Ws and there are more).

However they express an intent of what a class is (a service, a repository) and makes it clear to the user to what layer that class belongs.

However if you also use Spring for transaction managemnt then @Repository is also a trigger for adding exception translation to that class (also see the reference guide).

Although nothing has to break it probably will at some point.