JPA 2.0：嵌入式继承的抽象类

Question

I am using Spring Data JPA with Hibernate and I have the following classes

@Entity
@Table(name = "ORDER_SLIP")
public class OrderSlip {
    @EmbeddedId
    OrderNumber orderNumber;

    @Embedded
    OrderDetails orderDetails;
}

@Embeddable
public abstract class OrderDetail implements Serializable {

    String commonOrderDetailField;
}    

@Embeddable
public class BuyOrderDetail extends OrderDetail implements Serializable {

    String field1;
    String field2;
}        

@Embeddable
public class SellOrderDetail extends OrderDetail implements Serializable {

    String field3;
    String field4;
}

When I run the program, the fields in the OrderDetail class are embedded in the ORDER_SLIP table. The fields of the two subclasses of OrderDetail (BuyOrderDetail and SellOrderDetail) are not as I logically expect them to be.

Is this possible at all with JPA / Hibernate?

Answer 1

This is not possible. You should take a look at https://docs.jboss.org/hibernate/orm/4.3/manual/en-US/html_single/#inheritance

Answer 2

You can implement inheritance between @Embeddable classes. You just have to annotate the parent class with @MappedSuperclass too.

So, eg:

@Embeddable
@MappedSuperclass
public class Parent {
    @Basic
    private String parentProperty;

    // ... getters/setters
}

@Embeddable
public class Child extends Parent {
    @Basic
    private String childProperty;

    // ... getters/setters
}

This way Hibernate (tested with 5.x) will map both parentProperty and childProperty correctly in the Child class.

In your example you can take advantage of the inheritance only if you use one of your subtypes in the OrderSlip class (not the parent type).