我们有一个项目,我们需要懒惰地加载一个实体的集合,但在某些情况下我们需要它们急切地加载它们.我们在实体中添加了@NamedEntityGraph注释.在我们的存储库方法中,我们添加了一个“ javax.persistence.loadgraph”提示,以急切地加载在所述注释中定义的4个属性.当我们调用该查询时,Hibernate会抛出org.hibernate.loader.MultipleBagFetchException：无法同时获取多个包.

有趣的是,当我将所有这些集合重新定义为急切获取时,Hibernate会在没有MultipleBagFetchException的情况下急切地获取它们.

这是蒸馏代码.
实体：

@Entity
@NamedEntityGraph(name = "Post.Full",attributeNodes = {
        @NamedAttributeNode("comments"),@NamedAttributeNode("plusoners"),@NamedAttributeNode("sharedWith")
    }
)
public class Post {
    @OneToMany(cascade = CascadeType.ALL,mappedBy = "postId")
    private List<Comment> comments;

    @ElementCollection
    @CollectionTable(name="post_plusoners")
    private List<PostRelatedPerson> plusoners;

    @ElementCollection
    @CollectionTable(name="post_shared_with")
    private List<PostRelatedPerson> sharedWith;

}

查询方法(所有人都挤在一起让它可以发布)：

@Override
public Page<Post> findFullPosts(Specification<Post> spec,Pageable pageable) {
    CriteriaBuilder builder = entityManager.getCriteriaBuilder();
    CriteriaQuery<Post> query = builder.createQuery(Post.class);
    Root<Post> post = query.from(Post.class);
    Predicate postsPredicate = spec.toPredicate(post,query,builder);
    query.where(postsPredicate);

    EntityGraph<?> entityGraph = entityManager.createEntityGraph("PlusPost.Full");

    TypedQuery<GooglePlusFullPost> typedQuery = entityManager.createQuery(query);
    typedQuery.setHint("javax.persistence.loadgraph",entityGraph);

    query.setFirstResult(pageable.getOffset());
    query.setMaxResults(pageable.getPageSize());

    Long total = QueryUtils.executeCountQuery(getPostCountQuery(specification));

    List<P> resultList = total > pageable.getOffset() ? query.getResultList() : Collections.<P>emptyList();
    return new PageImpl<P>(resultList,pageable,total);
}

有关为什么在实体级别上使用热切提取而不是动态实体图形的任何提示？