Spring: Map Page to PageResponseModel-CodePudding

I've my PageableResponseModel class:

@NoArgsConstructor
@AllArgsConstructor
@Builder
@Getter
@Setter
public class PageableResponseModel<T> {
    private static final Integer DEFAULT_PAGE_SIZE      = 10;


    private Long totalResults;
    private Integer page;
    private Integer size;
    private List<T> results;
    
    public Integer getSize() {
        return
            Objects.nonNull(size)
                ? size
                : DEFAULT_PAGE_SIZE;
    }

    public void setSize(Integer size) {
        this.size =
            Objects.nonNull(size)
                ? size
                : DEFAULT_PAGE_SIZE;
    }
    
}

From my repositories, I'm getting org.springframework.data.domain.Page<T>:

Uni<Page<T>> findAll(Specification<T> spec, Pageable pageable);

I need to convert from org.springframework.data.domain.Page<T> to my PageableResponseModel<T>.

Any ideas?

CodePudding user response：

I would add private constructor, setting the fields by invoking the API provided by Page and its' superinterface Slice. And public static fromPage method to handle corner cases, nulls, etc.

@NoArgsConstructor
@AllArgsConstructor
@Builder
@Getter
@Setter
public class PageableResponseModel<T> {

  private static final Integer DEFAULT_PAGE_SIZE = 10;

  private Long totalResults;
  private Integer page;
  private Integer size;
  private List<T> results;

  //getters and setters omitted

  private PageableResponseModel(Page<T> page) {
    this.totalResults = page.getTotalElements();
    this.page = page.getNumber();
    this.size = page.getSize();
    this.results = page.getContent();
  }

  public static <R> PageableResponseModel<R> fromPage(Page<R> page) {
    if (page == null) {
      //some handling for your use case
      return new PageableResponseModel<>(Page.empty());
    }
    return new PageableResponseModel<>(page);
  }
}

CodePudding user response：

Create a constructor for PageableResponseModel

public PageableResponseModel(List<T> results, Integer page, Integer size, Long totalResults) {

    this.content = content;
    this.page = page;
    this.size = size;
    this.totalElements = totalElements;
}

Now in your service layer, first you need to check if the retrieved Page<T> has any elements or not. If it is empty, you can return a new object of

return new PageableResponseModel<>(Collections.emptyList(), page.getNumber(), 
       page.getSize(), page.getTotalElements());

Else, you get the list from the Page<T> using stream and map and feed the constructor like this

return new PageableResponseModel<>(list, page.getNumber(), page.getSize(), page.getTotalElements());