Q:

How to return 404 response status in Spring Boot @ResponseBody - method return type is Response?

I'm using Spring Boot with @ResponseBody based approach like the following:
@RequestMapping(value = VIDEO_DATA_PATH, method = RequestMethod.GET)
public @ResponseBody Response getData(@PathVariable(ID_PARAMETER) long id, HttpServletResponse res) {
    Video video = null;
    Response response = null;
    video = videos.get(id - 1);
    if (video == null) {
      // TODO how to return 404 status
    }
    serveSomeVideo(video, res);
    VideoSvcApi client =  new RestAdapter.Builder()
            .setEndpoint("http://localhost:8080").build().create(VideoSvcApi.class);
    response = client.getData(video.getId());
    return response;
}

public void serveSomeVideo(Video v, HttpServletResponse response) throws IOException  {
    if (videoDataMgr == null) {
        videoDataMgr = VideoFileManager.get();
    }
    response.addHeader("Content-Type", v.getContentType());
    videoDataMgr.copyVideoData(v, response.getOutputStream());
    response.setStatus(200);
    response.addHeader("Content-Type", v.getContentType());
}

I tried some typical approaches as:

res.setStatus(HttpStatus.NOT_FOUND.value());
  new ResponseEntity(HttpStatus.BAD_REQUEST);

but I need to return Response.
How to return here 404 status code if video is null?

A:

Create a NotFoundException class with an @ResponseStatus(HttpStatus.NOT_FOUND) annotation and throw it from your controller.
@ResponseStatus(code = HttpStatus.NOT_FOUND, reason = "video not found")
public class VideoNotFoundException extends RuntimeException {
}

A:

This is very simply done by throwing org.springframework.web.server.ResponseStatusException:
throw new ResponseStatusException(
  HttpStatus.NOT_FOUND, "entity not found"
);

It's compatible with @ResponseBody and with any return value. Requires Spring 5+

A:

Your original method can return ResponseEntity (doesn't change your method behavior):
@RequestMapping(value = VIDEO_DATA_PATH, method = RequestMethod.GET)
public ResponseEntity getData(@PathVariable(ID_PARAMETER) long id, HttpServletResponse res{
... 
}

and return the following:
return new ResponseEntity(HttpStatus.NOT_FOUND);

