Description
We are trying to use external REST API definition that would generate interfaces one implements in Java. For the time being we try to use Swagger.
Unfortunately Spring does not allow us to separate the API definition from implementation as the parameter annotations on controllers are not read from interfaces. Instead of that Spring always looks into the concrete implementation whose purpose is to implement a contract not define it. Weirdly enough the @RequestMapping annotation can be declared on the interface and is picked up by the implementing controller. It would be great if similar functionality is provided for @RequestBody, @PathVariable, @RequestHeader etc. that are defined on the individual parameters.
It seems that a potential fix has to update/extend the implementation of
Annotation[] org.springframework.core.MethodParameter.getParameterAnnotations()
this is called by
MethodParameter[] org.springframework.web.method.HandlerMethod.initMethodParameters()
called by the
org.springframework.web.method.HandlerMethod constructor which in turn is called by
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.createHandlerMethod(Object, Method).
There is a sample but hacky work around found on StackOverflow. See
http://stackoverflow.com/questions/8002514/spring-mvc-annotated-controller-interface/8005644#8005644
It does require some creativity to put in practical use with Spring Boot i.e. WebMvcRegistrations
So the basic ask is to pick up parameter annotations for controller from implemented interfaces e.g.
public interface MyControllerInterface {
@RequestMapping(path="/test", method=RequestMethod.POST)
public ResponseEntity<String> echo(@RequestBody String input);
}
@RestController
public class MyControllerImpl implements MyControllerInterface {
@Override
public ResponseEntity<String> echo(String input) {
return new ResponseEntity<>(input, HttpStatus.OK);
}
}
It may make sense to to use @RestController or alike annotation on the interfaces whose methods will be checked.