在我的项目中，我有三个实体：A，B和C：
@Entity
@Table(name = "ta_testA",catalog = "mytesdb")
public class A{
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="fiIdA")
private int fiIdA;
@OneToMany(mappedBy ="a", cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
private List<B> b
....(getters and setters)
}
@Entity
@Table(name = "ta_testB",catalog = "mytesdb")
public class B{
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="fiIdB")
private int fiIdB;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name="fiIdA")
private A a;
@OneToMany(mappedBy ="b", cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
private List<C> c
....(getters and setters)
}
@Entity
@Table(name = "ta_testC",catalog = "mytesdb")
public class C{
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="fiIdC")
private int fiIdC;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name="fiIdb")
private B b;
....(getters and setters)
}
public class ADAO extends CoreDAO {
public A getAById(int id) {
startOp();
A a;
try{
sesion.flush();
sesion.clear();
Query query = sesion.createQuery("Select a from"
+ " A as a where "
+ " (a.fiIdA = :id)");
a = (A) query.setParameter("id",id).uniqueResult();
}catch(HibernateException he){
System.out.println(he.getMessage());
throw he;
}finally{
sesion.close();
}
return a;
}
}
public class BDAO extends CoreDAO {
public B getBById(int id) {
startOp();
B b;
try{
sesion.flush();
sesion.clear();
Query query = sesion.createQuery("Select b from"
+ " B as b where "
+ " (b.fiIdB = :id)");
b = (B) query.setParameter("id",id).uniqueResult();
}catch(HibernateException he){
System.out.println(he.getMessage());
throw he;
}finally{
sesion.close();
}
return b;
}
}
如果我使用实体A DAO通过id检索对象，那么一切都很好，但是如果我只想获取B实体数据，则List属性会变得凌乱并返回很多重复数据。
如何从实体B仅获取数据，从而避免重复数据的问题？