public class GreeterService
        implements JsonService {
            public void handle(JsonRequest request, JsonResponse response) {
                if (request.isGet()) {
                    
                    var content = new JsonObject();
                    content.addProperty "message", "We rock!");
                    response.setContent(content);
                     

                    // ( missing code ||
                    //   a bug occurs here ||
                    //   no time to code )
                } else {
                    response.setStatusCode(400);
                }
            }
        }