@Nullable static String service(Invoker<?> invoker) {
    URL url = invoker.getUrl();
    if (url == null) return null;
    String service = url.getServiceInterface();
    return service != null && !service.isEmpty() ? service : null;
  }
@Test void service() {
    when(invoker.getUrl()).thenReturn(url);
    when(url.getServiceInterface()).thenReturn("brave.dubbo.GreeterService");

    assertThat(DubboParser.service(invoker))
        .isEqualTo("brave.dubbo.GreeterService");
  }