Calling REST API from MVC Controller (Spring MVC)

EDIT --

This is a stupid question - please ignore it. Going away to learn Java properly.

--

I want to create an API that can be used externally, but I also want to create my own front end to the same API.

If I create an MVC controller & a REST controller in the same app, can I call the REST API from the MVC controller without making an "external" http call, which seems a bit wasteful?

(EDIT - originally linked to another question but it ws wrong. Can't find the right one so removed).

Obviously raises the further question of whether I should or not, but that is, I suppose, subjective. As an aside I'd welcome opinion on that.

EDIT 2 (to add some code in response to chrylis)

So if I create a class like this (example copied from a tutorial somewhere)

public class Greeting {
    private final long id;
    private final String content;

    public Greeting(long id, String content) {
        this.id = id;
        this.content = content;
    }

    public long getId() {
        return id;
    }

    public String getContent() {
        return content;
    }   
}

and a rest controller like this which if called directly from the browser will return json data :

@RestController
public class GreetingController {

    private static final String template = "Hello, %s!";
    private final AtomicLong counter = new AtomicLong();

    @RequestMapping("/greeting")
    public Greeting greeting(@RequestParam(value="name", required=false, defaultValue="World") String name) {
        return new Greeting(counter.incrementAndGet(),
                            String.format(template, name));
    }
    
}

Then I call it from my HTML controller like this :

@Controller
public class HomeController {

    private static final Logger logger = LoggerFactory.getLogger(HomeController.class);
    
    @RequestMapping("/")
    public String home(Model model) {
        
        Greeting gr=new Greeting(1,"Hi");
        logger.info(gr.getContent());
        
        model.addAttribute("modelName",gr.getContent());
        return "home";
    }
}

is that what you mean? It seems to work. The only issue I see is that I'm working on the class directly and not performing the action of the rest api.

Actually, even as I write this I realise this isn't what you meant, I don't think.