        > 这里没指定 metadata 协议 port 的时候 是使用用户指定的应用协议呢？ 还是保持现在的 默认使用dubbo 但是 优化下 错误 提示

这里最好将默认值改成从用户环境中获取已经配置的额 protocol，都没配置再使用 dubbo

_Originally posted by @AlbumenJ in https://github.com/apache/dubbo/issues/10795#issuecomment-1289913950_
      
import org.apache.dubbo.config.ApplicationConfig;
import org.apache.dubbo.config.ArgumentConfig;
import org.apache.dubbo.config.MethodConfig;
import org.apache.dubbo.config.ProtocolConfig;
import org.apache.dubbo.config.RegistryConfig;
import org.apache.dubbo.config.ServiceConfig;
import org.apache.dubbo.metadata.MetadataService;
import org.apache.dubbo.registry.client.metadata.MetadataServiceDelegation;
import org.apache.dubbo.rpc.Protocol;
import org.apache.dubbo.rpc.ProtocolServer;
import org.apache.dubbo.rpc.model.ApplicationModel;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import static java.util.Collections.emptyList;
import static org.apache.dubbo.common.constants.CommonConstants.CORE_THREADS_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.DUBBO_PROTOCOL;
import static org.apache.dubbo.common.constants.CommonConstants.METADATA_SERVICE_PORT_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.METADATA_SERVICE_PROTOCOL_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.THREADPOOL_KEY;
import static org.apache.dubbo.common.constants.CommonConstants.THREADS_KEY;
import static org.apache.dubbo.common.constants.LoggerCodeConstants.CONFIG_FAILED_FIND_PROTOCOL;
import static org.apache.dubbo.common.constants.LoggerCodeConstants.CONFIG_METADATA_SERVICE_EXPORTED;
import static org.apache.dubbo.remoting.Constants.BIND_PORT_KEY;
/**
 * Export metadata service
 */
public class ConfigurableMetadataServiceExporter {