Question

我有两个名为SeriesDBModel和SermonDBModel的类;系列包含许多布道。

在SermonDBModel中，我有

@ManyToOne
@JoinColumn(name="series_id", nullable = false)
private SeriesDBModel series;

在SeriesDBModel中，我有

@JoinColumn(name="series_id")
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, orphanRemoval = true )
private List<SermonDBModel> sermons = new ArrayList<>();

我通过此调用持久保存数据（服务只包含标准的spring-data-jpa存储库），

final SeriesDBModel persisted = this.seriesDBService.save(seriesDBModel);

似乎写入数据库正常（db在sermons表中的seriesId中具有正确的值），并且使用SermonDBModel返回SeriesDBModel。但是，返回的SermonDBModel中的系列字段为null。

当前正在发生的是控制器通过服务保留数据，然后在将保存的模型对象转换回DTO以发送回调用者时，它失败（在Sermon类中），因为在布道模型对象上的关系未正确设置（即系列为空）。

控制器方法：

@RequestMapping(method = RequestMethod.POST,
            value = "/series",
            produces = APPLICATION_JSON_VALUE)
    public ResponseEntity<FBCApiResponse<Series>> create(@RequestBody SeriesDBModel seriesDBModel){

        FBCApiResponse<Series> response;
        if(seriesDBModel.getId() != null && seriesDBService.findById(seriesDBModel.getId()).isPresent()){
            logger.error("Can't create an entity that already exists");

            response = new FBCApiResponse<Series>(null,"Can't create an entity that already exists" );
        }
        else{
            logger.info(String.format("Saving or updating series %s", seriesDBModel));
            final SeriesDBModel persisted = this.seriesDBService.save(seriesDBModel);

            final Series series = new Series(persisted);

            response = new FBCApiResponse<Series>(series, HttpStatus.OK);
        }

        return new ResponseEntity<FBCApiResponse<Series>>(response, response.getStatusCode());
    }

系列DTO：

public Series(final SeriesDBModel seriesDBModel){

    this.id = seriesDBModel.getId();
    this.title = seriesDBModel.getTitle();
    this.imageURI = Optional.of(URI.create(seriesDBModel.getImageURL()));

    final List<SermonDBModel> sermonDBModels = seriesDBModel.getSermons();
    this.sermons = (CollectionUtils.isEmpty(sermonDBModels)) ?
            Optional.empty() :
            Optional.of(
                    sermonDBModels.stream()
                        .map(s -> Sermon.fromDBModel(s))
                    .collect(Collectors.toList())
            );

    final Stats stats = new Stats(seriesDBModel.getPlays(), seriesDBModel.getLikes(), seriesDBModel.getShares());
    this.stats = Optional.of(stats);

    this.tags = Optional.ofNullable(seriesDBModel.getTags()).map(tagList -> new HashSet<>(tagList));

}

Sermon DTO （由于系列为空，目前正在以NullpointerException爆炸）

public static Sermon fromDBModel(final SermonDBModel sermonDBModel){
    final int id = sermonDBModel.getId();
    final String title = sermonDBModel.getTitle();
    final String speaker = sermonDBModel.getSpeaker();
    final String series = sermonDBModel.getSeries().getTitle();
    final LocalDate date = sermonDBModel.getDate();
    final String seriesLink = "/series/" + sermonDBModel.getSeries().getId();

    final Optional<URI> mp3URI = Optional.ofNullable(sermonDBModel.getMp3Url()).map(URI::create);
    final Optional<URI> imageURI = Optional.ofNullable(sermonDBModel.getImageUrl()).map(URI::create);
    final Optional<URI> pdfURI = Optional.ofNullable(sermonDBModel.getImageUrl()).map(URI::create);


    final Stats stats = new Stats(sermonDBModel.getPlays(), sermonDBModel.getLikes(), sermonDBModel.getShares());

    final Optional<List<String>> tags = Optional.ofNullable(sermonDBModel.getTags());

    final Optional<Set<String>> tagSet = tags.map(list -> new HashSet(list));

    return new Sermon(id, title, speaker, series, Optional.of(seriesLink), date, mp3URI, imageURI, pdfURI, Optional.of(stats), tagSet);
}

注意，我可以通过在保留返回的Series后立即添加一行来“修复”此问题。但是，这似乎是一个黑客。为什么hibernate不会为我建立这种关系？

persisted.getSermons().forEach(sermon -> sermon.setSeries(persisted));

Spring Data JPA Hibernate ManyToOne Postgres在持久化时返回null

0 个答案: