为什么在 spring boot 中没有收到可分页的详细信息？

Question

我在 Spring Boot 项目中工作。我需要返回一个带分页的列表。目前我可以在参数中选择页面和大小，但我没有收到页面详细信息，例如：

"last": false,

"totalElements": 20,

"totalPages": 7,

"size": 3,

"number": 0,

"sort": null,

"first": true,

"numberOfElements": 3

我只是收到没有那个的正常回复。我想我需要将方法响应类型更改为 ResponseEntity 或 Resources。有任何想法吗？

控制器：

public List<PostOutputDTO> getTopicPosts(@PathVariable("id") UUID topicId, Pageable pageable) {

   return postService.getActivePosts(topicId, pageable);

服务：

 public List<PostOutputDTO> getActivePosts(UUID topicId, Pageable pageable) throws AccessDeniedException {

    Topic topic = topicRepo.findByIdAndDeactivatedAtIsNull(topicId).orElseThrow(() -> new EntityNotFoundException("This topic doesn't exist."));

    if (topic.getType() != TopicType.GLOBAL) {

        throw new AccessDeniedException("This is not a global topic.");

    }

    return postAssembler.toResources(postRepo.findPostsByTopicAndDeactivatedAtIsNull(topic, pageable));

}

汇编器：

@Service

public class PostAssembler extends ResourceAssemblerSupport<Post, PostOutputDTO> {

    @Autowired

    private ForumUserAssembler forumUserAssembler;

    @Autowired

    private TopicAssembler topicAssembler;

    @Autowired

    private ContentRepo contentRepo;

    public PostAssembler() {

        super(PostController.class, PostOutputDTO.class);

    }

    public PostOutputDTO toResource(Post post) {

        return PostOutputDTO.builder()

                .uuid(post.getId())

                .topic(topicAssembler.toResource(post.getTopic()))

                .text(contentRepo.findByPostAndDeactivatedAtIsNull(post).orElseThrow(() -> new EntityNotFoundException("This post doesn’t have content")).getText())

                .createdAt(post.getCreatedAt())

                .createdBy(forumUserAssembler.toResource(post.getCreatedBy()))

                .build();

    }

}

存储库：

@Repository

public interface TopicRepo extends JpaRepository<Topic, UUID> {

    Page<Topic> findAllByTypeAndDeactivatedAtIsNull(TopicType topicType, Pageable pageable);

}

Answer 1

将返回类型调整为Page<PostOutputDTO>而不是List<PostOutputDTO>。将 a 转换List<PostOutputDTO>为 a的最简单方法Page<PostOutputDTO>是public Page<PostOutputDTO> getTopicPosts(@PathVariable("id") UUID topicId, Pageable pageable) {&nbsp; &nbsp; return new PageImpl<>(postService.getActivePosts(topicId, pageable));}更新：我仍然没有看到全貌，但我希望存储库方法返回Page实例，Page<Post> findPostsByTopicAndDeactivatedAtIsNull(...);Page<Topic> findAllByTypeAndDeactivatedAtIsNull(...);所以问题来自于PostAssembler#toResources返回 a List，我们不准确地将其转换为Pageback 。如果我理解正确，您正在利用ResourceAssemblerSupport将 an Iterable<Post>（更准确地说， a Page<Post>）映射到 a List<PostOutputDTO>。我的建议是不使用PostAssembler#toResources，坚持PostAssembler#toResource和Page#map：postRepo.findPostsByTopicAndDeactivatedAtIsNull(topic, pageable)&nbsp; &nbsp; &nbsp; &nbsp; .map(postAssembler::toResource);

Answer 2

您必须从 spring 返回接口页面：页面是对象列表的子列表。它允许获取有关它在包含中的位置的信息。看例子：public Page<PostOutputDTO>&nbsp; getActivePosts(UUID topicId, Pageable pageable) {&nbsp; &nbsp; Page<PostOutputDTO>&nbsp; list=postService.getActivePosts(topicId, pageable);&nbsp; &nbsp; &nbsp; return&nbsp; list;}有关更多信息，请参阅参考