Spring Boot简明教程--Jpa分页

听城

发布于 2021-02-02 16:58:01

6450

发布于 2021-02-02 16:58:01

文章被收录于专栏：杂七杂八

分页参数

现在的分页形式有两种：

PC端分页，参数为：页码 page和每页的条数 size
小程序、app端分页，参数为：从第几条记录开始请求start，请求记录条数count

依赖

<dependency>
      <groupId>com.github.dozermapper</groupId>
      <artifactId>dozer-core</artifactId>
      <version>6.5.0</version>
</dependency>

定义分页参数业务类

@Getter
@Setter
@Builder
public class PageCounter {
    private Integer page;
    private Integer count;
}

两种参数转换

    public static PageCounter convertToPageParameter(Integer start, Integer count){
       int pageNum = start / count;
        PageCounter pageCounter = PageCounter.builder().page(pageNum).count(count).build();
        return pageCounter;
    }

分页对象构建

@Getter
@Setter
@NoArgsConstructor
public class Paging<T> {
    private Long total;
    private Integer count;
    private Integer page;
    private Integer totalPage;
    private List<T> items;

    public Paging(Page<T> pageT){
        this.initPageParameters(pageT);
        this.items = pageT.getContent();

    }
    void initPageParameters(Page<T> pageT){
        this.total = pageT.getTotalElements();
        this.count = pageT.getSize();
        this.page = pageT.getNumber();
        this.totalPage = pageT.getTotalPages();
    }
}

分页拷贝对象构建

通常情况下直接使用分页对象即可，但是某些时候我们需要将其转化为简化的VO对象，因此可通过该对象直接进行转化

public class PagingDozer<T,K> extends Paging{
    public PagingDozer(Page<T> pageT, Class<K> kClass){
        this.initPageParameters(pageT);
        List<T> tList = pageT.getContent();
        Mapper mapper = DozerBeanMapperBuilder.buildDefault();
        List<K> voList = new ArrayList<>();
        tList.forEach(t->{
            K vo = mapper.map(t,kClass);
            voList.add(vo);
        });
        this.setItems(voList);
    }
}

Controller层

    @GetMapping("/latest")
    public PagingDozer<Spu, SpuSimplifyVO> getLatestSpuList(@RequestParam(defaultValue = "0") Integer start,
                                                            @RequestParam(defaultValue = "10") Integer count){
        PageCounter pageCounter = CommonUtil.convertToPageParameter(start, count);
        Page<Spu> page = this.spuService.getLatestPagingSpu(pageCounter.getPage(), pageCounter.getCount());
        return new PagingDozer<>(page,SpuSimplifyVO.class);
    }

Service层

    public Page<Spu> getLatestPagingSpu(Integer pageNum, Integer size){
        Pageable page = PageRequest.of(pageNum, size, Sort.by("createTime").descending());
        return spuRepository.findAll(page);
    }

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