apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/controller/ReleaseHistoryController.java/ReleaseHistoryController/transform2PageDTO
class ReleaseHistoryController:  private PageDTO<ReleaseHistoryDTO> transform2PageDTO(Page<ReleaseHistory> releaseHistoriesPage, Pageable pageable){
    if (!releaseHistoriesPage.hasContent()) {
      return null;
    }

    List<ReleaseHistory> releaseHistories = releaseHistoriesPage.getContent();
    List<ReleaseHistoryDTO> releaseHistoryDTOs = new ArrayList<>(releaseHistories.size());
    for (ReleaseHistory releaseHistory : releaseHistories) {
      releaseHistoryDTOs.add(transformReleaseHistory2DTO(releaseHistory));
    }

    return new PageDTO<>(releaseHistoryDTOs, pageable, releaseHistoriesPage.getTotalElements());
  }