sample-auth.java

//1. Auth API

//Controller
class AuthenticationResource {
    //some implementation of interface is provided here
    private AuthenticationService authService;
    
    @Path("/authenticate")
    public Response authenticate(String username, String password){
        //call service and map exception
        
        
    }
}

//Service interface 
interface AuthenticationService{
    
    String authenticate(String username, String password) throws AuthFailException;
}