Hibernate Mapped Superclass relationships and overriding

Question

I have an abstract MappedSuperClass, Participant, which is extended by three kinds of 'Participant'. Each one then uses its own kind of 'Project', also an abstract MappedSuperClass. However, I want the base class to know about Projects so I can write generic code to interact with Participants. How do I specify this using Hibernate annotations? and how will I override it in the ExtendedParticipant and ExtendedProject classes?

Each Participant type, and each Project type, have their own database tables with existing data and ids (not unique across tables) that I cannot change.

The following code gives me the IDE error "Many to one attribute should not be 'Mapped Superclass'".

@MappedSuperclass
public abstract class Participant implements Persistable {

    ...

    @ManyToOne
    @JoinColumn(name = "project_id")
    public Project getProject() {
        return project;
    }

    public void setProject(Project project) {
        this.project = project;
    }

    ...
}

and the Project class is much the same with the same problem:

@MappedSuperclass
public abstract class Project implements Persistable {

    ...

    @OneToMany
    public List<Participant> getParticipants() {
        return participants;
    }

    public void setProject(List<Participant> participants) {
        this.participants = participants;
    }

    ...
}

score 11 · Accepted Answer · edited May 23 '17 at 12:08

11

A mapped superclass is not an Entity, it can't be part of an association. So map your classes as entities and either introduce a mapped superclass "above" them or use a TABLE_PER_CLASS strategy.

1

Thanks Pascal, that make sense. I saw another post you had commented on about this but I'm still unsure what to do about it. There must be a way to set up all the relationships using base classes? – Andrew Jul 12 '10 at 21:06
@Andrew: Well, why are they mapped superclass? Can't you put the common properties in a class above them? Another "option" would be to map them as entities and use a TABLE_PER_CLASS strategy. – Pascal Thivent Jul 12 '10 at 21:19
2

The 3 ExtendedParticipant classes share many field names, so I had hoped to put all that into the base class, which is why I chose a Mapped SuperClass. I guess I could have a base class with no mappings, but then I would have to include every field in every ExtendedParticipant... – Andrew Jul 12 '10 at 21:56

score 0 · Answer 2 · edited May 23 '17 at 12:19

0

Seems possible to have relations defined through the mappedsuperclass according to the following

edited May 23 '17 at 12:19

Community

1
1

answered Sep 06 '12 at 09:12

roshi

127
1
5

score 0 · Answer 3 · answered Mar 20 '19 at 15:01

0

Docs said it's possible, but superclass isn't abstract in example https://docs.oracle.com/javaee/5/api/javax/persistence/MappedSuperclass.html

answered Mar 20 '19 at 15:01

JeSa

559
4
11

Hibernate Mapped Superclass relationships and overriding

3 Answers3

See also

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