Saving entity with one-to-many relations with spring-data-jdbc returns empty list

Question

I have an issue with the return value after saving an item (ArticleList) with one-to-many relations(ArticleListEntry) in Spring Data JDBC. When creating an entity for the first time, upon calling repository.save(entity) my return entity, including all related items, are saved correctly in the database. However, the returned value contains an empty list for entries. The fields on the original ArticleList are always filled correctly.

I have the following entities:

@Table("article_list_meta")
@Data
public class ArticleList {
    @Id
    private final Long id;
    @Version
    private long version;
    @MappedCollection(idColumn = "list_id", keyColumn = "seq")
    private List<ArticleListEntry> entries = new ArrayList<>();  
    
    @PersistenceConstructor
    public ArticleList(Long id, String publication, String name) {
        this.id = id;
        this.publication = publication;
        this.name = name;
    }
    public ArticleList(String publication, String name) {
        this(null, publication, name);
    }
    // other fields
}

and

@Data
@Table("article_list_entry")
public class ArticleListEntry {

    @Column("article_id")
    private final long articleId;

}

With a repository

@Repository
public interface ArticleListRepository extends CrudRepository<ArticleList, Long> {}

I persist it using

        ArticleList entity = repository.findByPublicationAndName(publication, name)
                .orElseGet(() -> new ArticleList(publication, name));
        entity = mapper.fromDto(entity, list, fieldsToUpdate);
        ArticleList persistedEntity = repository.save(entity);

After the initial (version == 0) save, all following updates do include all related items. Note that an AbstractRelationalEventListener<ArticleList> receives the same entity-with-empty-list for the first call to save(articleList) (persistedEntity). The entity still contains the articles.

This leads me to believe I stumbled upon a bug, but since this is our first project using data-jdbc instead of data-jpa, there might also be something wrong in my entities.

I'm using Spring Boot 2.3.6.RELEASE with version 2.0.5.RELEASE of spring-data-jdbc.

Answer 1

This is an effect of entries not being part of the persistence constructor.

When a constructor is used to create a copy of an instance (e.g. because the id needs to be set), only the properties included in that constructor get copied over.

So in order to fix the problem you should modify the constructor of ArticleList to look like this:

@PersistenceConstructor
public ArticleList(Long id, String publication, String name, List<ArticleListEntry> entries) {
    this.id = id;
    this.publication = publication;
    this.name = name;
    this.entries = entries;
}