apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/controller/NamespaceController.java/NamespaceController/findByItem
class NamespaceController:  @GetMapping("/namespaces/find-by-item")
  public PageDTO<NamespaceDTO> findByItem(@RequestParam String itemKey, Pageable pageable) {
    Page<Namespace> namespacePage = namespaceService.findByItem(itemKey, pageable);

    List<NamespaceDTO> namespaceDTOS = BeanUtils.batchTransform(NamespaceDTO.class, namespacePage.getContent());

    return new PageDTO<>(namespaceDTOS, pageable, namespacePage.getTotalElements());
  }