apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/controller/NamespaceController.java/NamespaceController/find
class NamespaceController:  @GetMapping("/apps/{appId}/clusters/{clusterName}/namespaces")
  public List<NamespaceDTO> find(@PathVariable("appId") String appId,
                                 @PathVariable("clusterName") String clusterName) {
    List<Namespace> groups = namespaceService.findNamespaces(appId, clusterName);
    return BeanUtils.batchTransform(NamespaceDTO.class, groups);
  }