apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/AppNamespaceService.java/AppNamespaceService/findByAppIdAndNamespaces
class AppNamespaceService:  public List<AppNamespace> findByAppIdAndNamespaces(String appId, Set<String> namespaceNames) {
    Preconditions.checkArgument(!Strings.isNullOrEmpty(appId), "appId must not be null");
    if (namespaceNames == null || namespaceNames.isEmpty()) {
      return Collections.emptyList();
    }
    return appNamespaceRepository.findByAppIdAndNameIn(appId, namespaceNames);
  }