apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/NamespaceService.java/NamespaceService/loadNamespaceBO
class NamespaceService:  public NamespaceBO loadNamespaceBO(String appId, Env env, String clusterName,
      String namespaceName) {
    NamespaceDTO namespace = namespaceAPI.loadNamespace(appId, env, clusterName, namespaceName);
    if (namespace == null) {
      throw new BadRequestException("namespaces not exist");
    }
    return transformNamespace2BO(env, namespace);
  }