@Entity
public class E {
@GeneratedValue(strategy = GenerationType.AUTO)
@Id
int id;
String name;
@OneToMany(mappedBy = "e")
@MapKeyColumn(name = "kkk")
Map<String,F> f = new HashMap<String,F>();
}
@Entity
public class F {
@GeneratedValue(strategy = GenerationType.AUTO)
@Id
int id;
String name;
@ManyToOne
E e;
}
public class MapRelation {
public static void main(String[] args) {
EntityManagerFactory emf = Persistence
.createEntityManagerFactory("forcascade");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
E e = new E();
e.name = "i am e!";
F f1 = new F();
f1.name = "i am f1!";
F f2 = new F();
f2.name = "i am f2!";
f1.e = e;
f2.e = e;
em.persist(f1);
em.persist(f2);
e.f.put("f1", f1);
e.f.put("f2", f2);
em.persist(e);
em.getTransaction().commit();
em.close();
emf.close();
}
}
以上代码,JPA2.0双向一对多,在EclipseLink以及OpenJPA下运行没有问题,两个key "f1"与"f2"都存入数据库。但在Hibernate下,key没有存入数据库,失败鸟...
我们想,双向一对多,没有中间表,One将ID以及key存在Many表中,那么,应该可以在Many中设置One的persist cascade,最后提交Many既可以了...
@ManyToOne(cascade = {PERSIST,REMOVE})
E e;
在transaction之间的代码是这样的了,
E e = new E();
e.name = "i am e!";
F f1 = new F();
f1.name = "i am f1!";
f1.e = e;
e.f.put("f1", f1);
em.persist(f1);
F f2 = new F();
f2.name = "i am f2!";
f2.e = e;
e.f.put("f2", f2);
em.persist(f2);
高兴的是,EclipseLink与OpenJPA仍然没有让我们失望;杯具地是,Hibernate仍然让我们失望了...