apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/NamespaceService.java/NamespaceService/loadNamespaceBaseInfo
class NamespaceService:  public NamespaceDTO loadNamespaceBaseInfo(String appId, Env env, String clusterName,
      String namespaceName) {
    NamespaceDTO namespace = namespaceAPI.loadNamespace(appId, env, clusterName, namespaceName);
    if (namespace == null) {
      throw new BadRequestException(String.format("Namespace: %s not exist.", namespaceName));
    }
    return namespace;
  }