我有以下几个层次JPA TABLE_PER_CLASS问题多对一
@MappedSuperclass
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class Order {
...
@Entity
@Table(name = "b_order", schema = "public")
public class BOrder extends Order implements java.io.Serializable {
...
@Entity
@Table(name = "s_order", schema = "public")
public class SOrder extends Order implements java.io.Serializable {
我也有tr之后双方的具体子类的引用
@Entity
@Table(name = "tr", schema = "public")
public class Tr implements java.io.Serializable {
...
private SOrder sOrder;
private BOrder bOrder;
...
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "s_order_id", nullable = false)
public SOrder getSOrder() {
return this.sOrder;
}
... same for BOrder
定义为上述延迟加载作品类的类罚款:
Tr foundTr = trDAO.findById(trId);
// test lazy loading BOrder, SOrder
BOrder foundBOrder = foundTr.getBOrder();
SOrder foundSOrder = foundTr.getSOrder();
assertNotNull(foundSOrder);
assertNotNull(foundBOrder);
但是,如果我尝试执行多态查询它不起作用:
public List<Order> getOrdersByUId(Long uId) {
return (List<Order>) em.createQuery(//
" select o from Order o " //
+ " order by o.created desc ") //
.getResultList();
我得到一个错误:
基于这个帖子Order is not mapped
:http://java.dzone.com/articles/jpa-implementation-patterns-mapping
BTW, when using Hibernate proxies, be aware that lazily loading a class mapped with any of the three strategies above always returns a proxy that is an instanceof the superclass. Blockquote
其奇怪的行为,我看到的相匹配。
但是,这是奇怪的地方。如果我父类更改为
@Entity
// @MappedSuperclass
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class Order {
这是我注释掉MappedSuperClass注释,多态查询作品(创建正确工会)。 问题是当我这样做时,从Tr到两个子类的LAZY加载停止工作。
任何想法?我可以使用本机查询来执行联合而不是JPA吗?
我到JBoss 6.0.0使用JPA 2.0使用Hibernate - 任何版本附带的JBoss
我想你说得对。我遇到了类似的问题,为@Entity交换@ MappedSuperClass修复了它。我从来没有直接询问具体的实现,但查询父母没有为我工作......直到现在。 – spaaarky21