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.