Spring MVC Annotated Controller Interface with @PathVariable

Question

Is there any reason not to map Controllers as interfaces?

In all the examples and questions I see surrounding controllers, all are concrete classes. Is there a reaso

Answer 1

The feature of defining all bindings on interface actually got implement recently in Spring 5.1.5.

Please see this issue: https://github.com/spring-projects/spring-framework/issues/15682 - it was a struggle :)

Now you can actually do:

@RequestMapping("/random")
public interface RandomDataController {

    @RequestMapping(value = "/{type}", method = RequestMethod.GET)
    @ResponseBody
    RandomData getRandomData(
            @PathVariable(value = "type") RandomDataType type, @RequestParam(value = "size", required = false, defaultValue = "10") int size);
}

@Controller
public class RandomDataImpl implements RandomDataController {

    @Autowired
    private RandomGenerator randomGenerator;

    @Override
    public RandomData getPathParamRandomData(RandomDataType type, int size) {
        return randomGenerator.generateRandomData(type, size);
    }
}

You can even use this library: https://github.com/ggeorgovassilis/spring-rest-invoker

To get a client-proxy based on that interface, similarly to how RestEasys client framework works in the JAX-RS land.