- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [ ] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.6-SNAPSHOT
* Operating System version: Mac
* Java version: 1.8

### Steps to reproduce this issue

run dubbo-samples-stub sample

### Expected Result

"stub - greeting dubbo"

### Actual Result

return "greeting dubbo"

import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.common.utils.ConfigUtils;
import org.apache.dubbo.common.utils.NetUtils;
import org.apache.dubbo.common.utils.ReflectUtils;
import org.apache.dubbo.common.utils.StringUtils;
import org.apache.dubbo.rpc.Exporter;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Protocol;
import org.apache.dubbo.rpc.ProxyFactory;
import org.apache.dubbo.rpc.RpcException;
import org.apache.dubbo.rpc.service.GenericService;
import java.lang.reflect.Constructor;
import static org.apache.dubbo.common.constants.CommonConstants.STUB_EVENT_KEY;
import static org.apache.dubbo.rpc.Constants.DEFAULT_STUB_EVENT;
import static org.apache.dubbo.rpc.Constants.IS_SERVER_KEY;
import static org.apache.dubbo.rpc.Constants.LOCAL_KEY;
import static org.apache.dubbo.rpc.Constants.STUB_EVENT_METHODS_KEY;
import static org.apache.dubbo.rpc.Constants.STUB_KEY;
/**
 * StubProxyFactoryWrapper
 */
public class StubProxyFactoryWrapper implements ProxyFactory {
    private static final Logger LOGGER = LoggerFactory.getLogger(StubProxyFactoryWrapper.class);
    private final ProxyFactory proxyFactory;
    private Protocol protocol;
    public StubProxyFactoryWrapper(ProxyFactory proxyFactory) {
        this.proxyFactory = proxyFactory;
    }
    public void setProtocol(Protocol protocol) {
        this.protocol = protocol;