分页Page对象使用

之前不管是mysql还是mongo等数据库，都喜欢自己造轮子去做分页查询。现在用Page来实现分页

下面实现2个功能点：

1、查询勋章实体的Page，含分页信息、勋章列表

2、勋章Page转勋章DTO对象Page，dto为列表功能所需数据。使用语法：new PageImpl(dtoList, pageable, medalPage.getTotalElements()

public Page<MedalListDTO> listMedal(Pageable pageable, MedalListQuery medalListQuery) {
    Criteria criteria = new Criteria();
    if (null != medalListQuery.getStatus()) {
        criteria = criteria.and("status").is(medalListQuery.getStatus());
    }
    if(StringUtils.isNotBlank(medalListQuery.getChannelId())){
        criteria = criteria.and("channelId").is(medalListQuery.getChannelId());
    }
    if(StringUtils.isNotBlank(medalListQuery.getName())){
        criteria = criteria.and("name").is(medalListQuery.getName());
    }
    // 获取勋章的pege对象
    Page<Medal> medalPage = medalRepository.findBy(criteria, pageable); 
    List<Medal> medals = medalPage.getContent();

　　 List<MedalListDTO> dtoList = medals.stream().map(new Function<Medal, MedalListDTO>() {
    　　@Override
    　　public MedalListDTO apply(Medal medal) {
        　　MedalListDTO dto = new MedalListDTO();
           xxx....
           return dto;
       }
　　 }).collect(Collectors.toList());

　　 return new PageImpl(dtoList, pageable, medalPage.getTotalElements()；

}

Page接口如下：

public interface Page<T> extends Slice<T> {
    static <T> Page<T> empty() {
        return empty(Pageable.unpaged());
    }

    static <T> Page<T> empty(Pageable pageable) {
        return new PageImpl(Collections.emptyList(), pageable, 0L);
    }

    int getTotalPages();

    long getTotalElements();

    <U> Page<U> map(Function<? super T, ? extends U> var1);
}

返回值：

{
  "rt": {
    "status": 200,
    "appId": "xxx",
    "debug": null
  },
  "data": {
    "content": [
      {
        "id": "82a21594-8bf3-44a9-a2f2-f3554a958cf0",
        "name": "11",
        "channelName": "22",
        "taskTeamName": "22222",
        "createdDate": "2020-05-28T08:58:15.843+0000",
        "status": "已上架",
        "passRate": 0.92,
        "joinedCount": 3,
        "passedCount": 3,
        "passedRate": 1,
        "questionsCount": 10
      }
    ],
    "pageable": {
      "sort": {
        "sorted": false,
        "unsorted": true,
        "empty": true
      },
      "offset": 0,
      "pageNumber": 0,
      "pageSize": 2,
      "paged": true,
      "unpaged": false
    },
    "totalElements": 4,
    "totalPages": 2,
    "last": false,
    "size": 2,
    "number": 0,
    "sort": {
      "sorted": false,
      "unsorted": true,
      "empty": true
    },
    "numberOfElements": 2,
    "first": true,
    "empty": false
  },
  "success": true
}