code: @Test public void testConfig(){
    com.alibaba.dubbo.config.ServiceConfig<DemoService> service=new ServiceConfig<>();
    service.setApplication(new com.alibaba.dubbo.config.ApplicationConfig("first-dubbo-provider"));
    service.setRegistry(new com.alibaba.dubbo.config.RegistryConfig("multicast://224.5.6.7:1234"));
    service.setInterface(DemoService.class);
    service.setRef(new DemoServiceImpl());
    service.export();
    com.alibaba.dubbo.config.ReferenceConfig<DemoService> reference=new ReferenceConfig<>();
    reference.setApplication(new ApplicationConfig("first-dubbo-client"));
    reference.setRegistry(new RegistryConfig("multicast://224.5.6.7:1234"));
    reference.setInterface(DemoService.class);
    DemoService demoService=reference.get();
    String message=demoService.sayHello("dubbo");
    Assert.assertEquals("hello dubbo",message);
  }
  