[英]how to mapping an OneToMany relation with Weak Entity in Hibernate
[英]Entity class mapping in hibernate, complex relation
我有四个类(A,B,C,D)都按关系连接。 我正在使用hibernate将它们存储在mysql数据库中。
课程结构
Class A {
Integer id; //primary key
List<B> listOfB; //one to many with B class, able to store order of B's
//some other fields
}
/* This class can contain list of c, or list of d, or both.
* need to keep order among c and d also if contains both list
* for eg, B has list of c(c1, c2, c3) and D (d1, d2, d3)
* order can be c1, d1, c2, d3, c3, d2
*/
Class B {
Integer id; //primary key
List<C> listOfC; //one to many with D class, able to store order of C's
List<D> listOfD; //one to many with C class, able to store order of D's
//How to store order between list of c and list of d?
//some other field
}
Class C {
Integer id; //primary key
List<D> listOfD; //one to many with D class, able to store order of D's
//some other field
}
Class D {
Integer id; //primary key
String value; //some value
}
这里A和B之间的关系是一对多,B到C是一对多,B到D是一对多,C到D是一对多。
List仅用于跟踪对象之间的顺序。 但我也想跟踪B类中c和d列表的顺序。
B can have following steps:
1. C1
2. D1
3. c2
4. D2
使用当前设计,我无法在c和d之间存储顺序。
请提出一些设计。 谢谢
您可以从抽象实体继承C
和D
,并在B
使用单个列表。
抽象实体:
@Entity
@Inheritance
@DiscriminatorColumn(name = "discr")
public abstract class X {
Integer id;
// ...
}
然后扩展它:
@Entity
@DiscriminatorValue("c")
public class C extends X {
List<D> listOfD;
// ...
}
@Entity
@DiscriminatorValue("d")
public class D extends X {
String value;
// ...
}
最后:
@Entity
public class B {
Integer id;
List<X> listOfX; // single list for C and D
}
看一下继承状态 。 在我的例子中,我使用的是单表策略。
另外看看这个
显然你需要添加关系注释。
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