apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/api/AdminServiceAPI.java/AdminServiceAPI/findByItem
class AdminServiceAPI:    public PageDTO<NamespaceDTO> findByItem(Env env, String itemKey, int page, int size) {
      ResponseEntity<PageDTO<NamespaceDTO>>
          entity =
          restTemplate.get(env, "/namespaces/find-by-item?itemKey={itemKey}&page={page}&size={size}",
                           namespacePageDTO, itemKey, page, size);
      return entity.getBody();
    }