Why does Spring Boot not read the PathVariable that is defined on my interface resource?

Question

I am using a custom code generator to transform a REST contract in to Java interfaces. Below find a sample of a generated resource Java interface.

@Generated(
    date = "2018-01-30T11:56:25.156Z",
    comments = "Specification filename: country.v1.json",
    value = "GENERATOR"
)
@RequestMapping("/v1/countries")
public interface CountriesResource {

  @RequestMapping(
      method = RequestMethod.GET,
      path = "/{id}",
      produces = MediaType.APPLICATION_JSON_VALUE
  )
  @ResponseBody
  LandGetResourceModel getEntity(@PathVariable("id") String id);
}

Additionally the generator creates an @RestController implementation a that interface for Spring to create a controller bean.

@RestController
public class CountriesResourceImpl implements CountriesResource {

    @Override
    public CountryGetResourceModel getEntity(String id) {
        return new CountryGetResourceModel();
    }
}

So far everything works fine. Spring creates the RestController bean and the HTTP calls are directed correctly to the corresponding Handler method (e.g. getEntity).

The problem is that for some reason Spring is not able to resolve path variables when they are defined on the interface. All calls containing a path variable are handled but the method parameter of any path variable is null. If I then add the PathVariable annotation to the implementation class Spring is able to resolve the corresponding value.

Is there a way to tell Spring to read the PathVariable from the interface method declaration like it does for the RequestMapping annotations?

yes, but seems like it won't help you. look what I've found: https://jira.spring.io/browse/SPR-11055 — Dmitry Senkovich, Jan 31 '18 at 07:17
..and explanation https://stackoverflow.com/a/8005644/5185646 — Dmitry Senkovich, Jan 31 '18 at 07:17
What a pitty :( Well it seems I have to generate some decorators classes for that resource Interface and then delegate the calls to the implementation class. — saw303, Jan 31 '18 at 07:20

score 2 · Accepted Answer · answered Jan 31 '18 at 07:23

Unfortunately, seems like it is a known issue. I've found the following opened Jira on the question. Some explanation can be found from this answer. Also, in the same question I took the previous answer I see this solution. However, I haven't tried it and it seems to be heavy.

Why does Spring Boot not read the PathVariable that is defined on my interface resource?

1 Answers1