import org.apache.hadoop.ipc.protobuf.ProtocolInfoProtos.GetProtocolVersionsRequestProto; //导入依赖的package包/类
@Override
public GetProtocolVersionsResponseProto getProtocolVersions(
    RpcController controller, GetProtocolVersionsRequestProto request)
    throws ServiceException {
  String protocol = request.getProtocol();
  GetProtocolVersionsResponseProto.Builder builder = 
      GetProtocolVersionsResponseProto.newBuilder();
  for (RPC.RpcKind r : RPC.RpcKind.values()) {
    long[] versions;
    try {
      versions = getProtocolVersionForRpcKind(r, protocol);
    } catch (ClassNotFoundException e) {
      throw new ServiceException(e);
    }
    ProtocolVersionProto.Builder b = ProtocolVersionProto.newBuilder();
    if (versions != null) {
      b.setRpcKind(r.toString());
      for (long v : versions) {
        b.addVersions(v);
      }
    }
    builder.addProtocolVersions(b.build());
  }
  return builder.build();
}