加载一些对象时我有一个奇怪的问题.我使用JPA 1,hibernate-core版本3.3.0.SP1和hibernate-entitymanager版本3.4.0.GA
假设我有这些JPA实体:
- @Entity
- @Table(name = "SLC_ELE")
- @Inheritance(strategy = InheritanceType.JOINED)
- @DiscriminatorColumn(discriminatorType = DiscriminatorType.INTEGER,name = ElementoPrograma.C_ID_CTG_ELE)
- public class Element {
- ...
- }
- @Entity
- @Table(name = "SLC_ELE_ONE")
- @Inheritance(strategy = InheritanceType.JOINED)
- @DiscriminatorValue(Categories.ID_CTG_ONE)
- public class ElementTypeOne extends Element {
- ...
- }
- @Entity
- @Table(name = "SLC_ELE_TWO")
- @Inheritance(strategy = InheritanceType.JOINED)
- @DiscriminatorValue(Categories.ID_CTG_TWO)
- public class ElementTypeTwo extends Element {
- ...
- }
- @Entity
- @Table(name = ThreeElementExample.TABLENAME)
- @AssociationOverrides({
- @AssociationOverride(name = JpaMany3ManyEntity.ASOCIATION_OVERRIDE_ONE,joinColumns =
- @JoinColumn(name = Element.C_ID_ELE)),@AssociationOverride(name = JpaMany3ManyEntity.ASOCIATION_OVERRIDE_TWO,joinColumns =
- @JoinColumn(name = OneEntity.C_ID_TWO)),@AssociationOverride(name = JpaMany3ManyEntity.ASOCIATION_OVERRIDE_THREE,joinColumns =
- @JoinColumn(name = AnotherEntity.C_ID_THREE))})
- public class ThreeElementExample extends JpaMany3ManyEntity<Element,OneEntity,AnotherEntity> {
- ...
- }
事情是,当我加载这些实体的集合时,我想永远获得子类(意思是ElementTypeOne,ElementTypeTwo而不是元素).问题是,许多关系总是得到元素(父亲而不是孩子)
假设我有一个实体A包含一个元素的集合:
- @Fetch(FetchMode.JOIN)
- @OneToMany(cascade = CascadeType.ALL,mappedBy = "idEle")
- private Collection<Element> elementCollection;
如果我收集,一切都正常(我按预期得到子类).
当我有另一个实体B与JpaMany3ManyEntity的集合(注意涉及相同的实体元素)时,问题出现了
- @OneToMany(cascade = CascadeType.ALL,mappedBy = JpaMany3ManyEntity.ASOCIATION_OVERRIDE_ONE,fetch = FetchType.LAZY)
- private Collection<ThreeElementExample> threeElementExampleCollection;
如果我从类B中循环了三个EementExampleCollection,然后我尝试从类A获取elementCollection,当我从elementCollection加载对象
我只是获取超类(Element)对象,而不是孩子.
我猜,由于任何原因,多对多的关系总是获取Element对象(父),并将它们保存在hibernate缓存中,但是我需要避免这种情况.
任何想法或工作环境?任何形式的帮助将非常感激.
提前致谢.
编辑:多对多课:
- @SuppressWarnings("serial")
- @MappedSuperclass
- @AssociationOverrides({
- @AssociationOverride(name = JpaMany3ManyEntity.ASOCIATION_OVERRIDE_ONE,joinColumns =
- @JoinColumn(name = "changeMeWhenExtends")),joinColumns =
- @JoinColumn(name = "changeMeWhenExtends"))})
- public abstract class JpaMany3ManyEntity<A extends JpaBaseEntity,B extends JpaBaseEntity,C extends JpaBaseEntity> extends JpaBaseEntity {
- public static final String ID_ATTNAME = "id";
- public static final String ASOCIATION_OVERRIDE_ONE = JpaMany3ManyEntity.ID_ATTNAME + "." + JpaMany3ManyId.ID_ONE_ATTNAME;
- public static final String ASOCIATION_OVERRIDE_TWO = JpaMany3ManyEntity.ID_ATTNAME + "." + JpaMany3ManyId.ID_TWO_ATTNAME;
- public static final String ASOCIATION_OVERRIDE_THREE = JpaMany3ManyEntity.ID_ATTNAME + "." + JpaMany3ManyId.ID_THREE_ATTNAME;
- ...
- }
解决方法
这是一个工作环境,适用于我:脱离实体.
即使拥有实体的父代理(jpa.inheritance.issue.Element _ $$_ javassist_1),如果你去掉它,你将获得真正的实体(子).
假设你想要从实体A循环你的(子)元素集合,然后与它们做一些事情.
就像是:
- public void loopDeproxyElements(List<Element> yourElementsCollection){
- for(Element p : yourElementsCollection){
- if(p instanceof HibernateProxy){
- Element child = (Element) ((HibernateProxy) p).getHibernateLazyInitializer()
- .getImplementation();
- if (child instanceof ElementTypeOne){
- //You can cast your object or do whatever you want,knowing for sure that's a child element)
- ElementTypeOne myRealElement = (ElementTypeOne) child;
- ...
- } else {
- //It should be ElementTypeTwo (if u never create parent entities)
- ...
- }
- }
- }
- )
它总是会像我所期待的那样得到孩子的元素.