休眠中的實體類映射，複雜關係

Question

我有四個類（A，B，C，D）都是通過關係連接的。我正在使用hibernate將它們存儲在mysql數據庫中。類

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 

} 

A和B之間的關係在這裏是一對多

結構，B到C是一對多，B至d是一對多，C至d是一對多的。

列表僅用於跟蹤對象之間的順序。但是我也想跟蹤B類中c和d列表的順序。

B can have following steps: 
1. C1 
2. D1 
3. c2 
4. D2 

在目前的設計中，我無法存儲c和d之間的順序。

請建議一些設計。謝謝

Answer 1

您可以從一個抽象實體繼承C和D並使用B中的單個列表。

抽象實體：

@Entity 
@Inheritance 
@DiscriminatorColumn(name = "discr") 
public abstract class X { 
    Integer id; 
    // ... 
} 

然後擴展它：

@Entity 
@DiscriminatorValue("c") 
public class C extends X { 
    List<D> listOfD; 
    // ... 
} 

@Entity 
@DiscriminatorValue("d") 
public class D extends X { 
    String value;  
    // ... 
} 

最後：

@Entity 
public class B { 
    Integer id; 
    List<X> listOfX; // single list for C and D 
} 

在inheritance stategies看看。在我的例子中，我使用單表策略。

也看看到this

顯然，你需要添加關係註解。