Question

我的 Item.java 实体具有以下属性

@OneToMany(cascade=CascadeType.ALL, mappedBy="kitItem", fetch=FetchType.EAGER) 
private Set<KitItemDetails> kitItemDetails = new HashSet<KitItemDetails>(0);

.... Other properties with getter and setter

我的 KitItemDetails.java 实体具有以下属性

@ManyToOne(cascade=CascadeType.ALL)  
private Item kitItem;

在我的DAO访问类中，我们使用以下查询来获取具有其他相关属性的所有项目，如EAGER

List<Item> items = getCurrentSession().createCriteria(Item.class).addOrder(Order.asc("itemOrder"))
                .list();

但是为此它点击n选择查询项目详细信息如下

select kititemdet0_.kitItem_id as kitItem_2_9_0_, kititemdet0_.id as id1_12_0_, kititemdet0_.id as id1_12_1_, kititemdet0_.kitItem_id as kitItem_2_12_1_, kititemdet0_.ITEM_ID as ITEM_ID3_12_1_, item1_.id as id1_9_2_, item1_.BAR_CODE as BAR_CODE2_9_2_, item1_.COLOR_CODE as COLOR_CO3_9_2_, item1_.IS_ACTIVE as IS_ACTIV4_9_2_, item1_.ITEM_CATEGORY_ID as ITEM_CA14_9_2_, item1_.ITEM_CODE as ITEM_COD5_9_2_, item1_.ITEM_DISP_NAME as ITEM_DIS6_9_2_, item1_.ITEM_IMAGE as ITEM_IMA7_9_2_, item1_.ITEM_NAME as ITEM_NAM8_9_2_, item1_.ITEM_ORDER as ITEM_ORD9_9_2_, item1_.ITEM_PRICE as ITEM_PR10_9_2_, item1_.ITEM_PRICE_WITH_TAX as ITEM_PR11_9_2_, item1_.ITEM_SUB_CATEGORY_ID as ITEM_SU15_9_2_, item1_.ITEM_TYPE as ITEM_TY12_9_2_, item1_.TAX_ID as TAX_ID16_9_2_, item1_.TAX_CODE as TAX_COD13_9_2_, itemcatego2_.id as id1_10_3_, itemcatego2_.COLOR_CODE as COLOR_CO2_10_3_, itemcatego2_.IS_ACTIVE as IS_ACTIV3_10_3_, itemcatego2_.ITEM_CATEGORY_NAME as ITEM_CAT4_10_3_, itemcatego2_.LOCATION_ID as LOCATION6_10_3_, itemcatego2_.PRINTER_NAME as PRINTER_5_10_3_, itemsubcat3_.id as id1_11_4_, itemsubcat3_.COLOR_CODE as COLOR_CO2_11_4_, itemsubcat3_.IS_ACTIVE as IS_ACTIV3_11_4_, itemsubcat3_.ITEM_CATEGORY_ID as ITEM_CAT5_11_4_, itemsubcat3_.ITEM_SUB_CATEGORY_NAME as ITEM_SUB4_11_4_, tax4_.id as id1_21_5_, tax4_.IS_ACTIVE as IS_ACTIV2_21_5_, tax4_.LOCATION_ID as LOCATION6_21_5_, tax4_.TAX_CODE as TAX_CODE3_21_5_, tax4_.TAX_NAME as TAX_NAME4_21_5_, tax4_.TAX_PER as TAX_PER5_21_5_ from KIT_ITEM_DETAILS kititemdet0_ inner join ITEM item1_ on kititemdet0_.ITEM_ID=item1_.id left outer join ITEM_CATEGORY itemcatego2_ on item1_.ITEM_CATEGORY_ID=itemcatego2_.id left outer join ITEM_SUB_CATEGORY itemsubcat3_ on item1_.ITEM_SUB_CATEGORY_ID=itemsubcat3_.id left outer join TAX tax4_ on item1_.TAX_ID=tax4_.id where kititemdet0_.kitItem_id=?

我尝试使用mappedBy，JoinColumn，JoinType，FetchMode等，但没有解决，可能是什么问题？

Answer 1

通常，将关系设置为EAGER会导致＆＃34; N选择查询＆＃34;使用条件查询时出现问题。您可以通过明确指示Hibernate执行获取连接来克服此问题。有关详细信息，请参阅the Hibernate documentation。

该文档包含一个与您的场景非常相似的示例（调整为使用您的类名称）：

CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<Item> query = builder.createQuery( Item.class );
Root<Item> root = query.from( Item.class );
root.fetch( "kitItemDetails", JoinType.LEFT);
query.select(root).where(
   builder.and(
     builder.equal(root.get("foo"), foo),
     builder.equal(root.get("bar"), bar)
  )
);
Item item = entityManager.createQuery( query ).getSingleResult();
// Alternatively, .getResultList() to return List<Item>

@Fetch(FetchMode.JOIN)在您的情况下不起作用，因为文档继续在FetchMode.JOIN的示例中声明：

我们之所以不使用JPQL查询来获取多个Department实体，是因为查询提取指令会覆盖FetchMode.JOIN策略。

Hibernate n选择具有双向相同实体关系的问题

1 个答案: