apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/ConfigsImportService.java/ConfigsImportService/forceImportNamespaceFromFile
class ConfigsImportService:  public void forceImportNamespaceFromFile(final Env env, final String standardFilename,
                                           final InputStream zipInputStream) {
    String configText;
    try (InputStream in = zipInputStream) {
      configText = ConfigToFileUtils.fileToString(in);
    } catch (IOException e) {
      throw new ServiceException("Read config file errors:{}", e);
    }

    currentUser = userInfoHolder.getUser().getUserId();

    this.importNamespaceFromText(env, standardFilename, configText, false);
  }