@Override
    public HttpResponse serve(ServiceRequestContext ctx, HttpRequest req) throws Exception {
        assert decorated != null;
        final ServerMethodDefinition<?, ?> methodDefinition = methodDefinition(ctx);
        if (methodDefinition == null) {
            return delegate.serve(ctx, req);
        }
        final HttpService decoratedService = decorated.get(methodDefinition);
        if (decoratedService != null) {
            return decoratedService.serve(ctx, req);
        }
        return delegate.serve(ctx, req);
    }
A Wrapper class for {@link GrpcService} to route decorated function according to a request path.
grpc/src/main/java/com/linecorp/armeria/server/grpc/GrpcDecoratingService.java