code: @Test public void testEcho(){
    DemoService server=new DemoServiceImpl();
    ProxyFactory proxyFactory=ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();
    Protocol protocol=ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
    URL url=URL.valueOf("dubbo://127.0.0.1:5342/" + DemoService.class.getName() + "?version=1.0.0");
    Exporter<DemoService> exporter=protocol.export(proxyFactory.getInvoker(server,DemoService.class,url));
    Invoker<DemoService> invoker=protocol.refer(DemoService.class,url);
    EchoService client=(EchoService)proxyFactory.getProxy(invoker);
    Object result=client.$echo("haha");
    Assert.assertEquals("haha",result);
    org.apache.dubbo.rpc.service.EchoService newClient=(org.apache.dubbo.rpc.service.EchoService)proxyFactory.getProxy(invoker);
    Object res=newClient.$echo("hehe");
    Assert.assertEquals("hehe",res);
    invoker.destroy();
    exporter.unexport();
  }
  