CODEWITHSUNDEEP
javahibernatespring-data-jpa
Theo Michail
Theo Michail

Reputation: 186

Hibernate embed a mapped superclass

I am trying to use @ElementCollection with a set of classes which are all inherited from a @MappedSuperclass but when persisting to the database there is no column to identify which subclass was created and therefore will fail when trying to retrieve it from the database. If I change the class to make it an entity instead it will then work but I need it to be @Embeddable to work with @ElementCollection

Below is the code:

@Entity
public class A {
    private String attr1;
    private String attr2;
    ....
    @ElementCollection
    private List<B> list;

    ....
}

Superclass:

@Embeddable
@MappedSuperclass
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class B {
    private String attr3
    private String attr4

    ....
}

Subclass1:

@Embeddable
@DiscriminatorValue("B1")
public class B1 extends B {
    private String attr5

    ....
}

Subclass2:

@Embeddable
@DiscriminatorValue("B2")
public class B2 extends B {
    private String attr6

    ....
}

Thanks in advance

Upvotes: 0

Views: 713

Answers (1)

Christian Beikov
Christian Beikov

Reputation: 16462

@ElementCollection is for basic or embeddable values which both have no concept of inheritance. If you want inheritance, you need to model the value as entity and then use @OneToMany. From a relational mapping perspective, the two mappings are almost the same:

@Entity
public class A {
    private String attr1;
    private String attr2;
    ....
    @OneToMany(mappedBy = "a")
    private List<B> list;

    ....
}

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public abstract class B {
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "a_id")
    private A a;
    private String attr3
    private String attr4

    ....
}

Upvotes: 1

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