JPA: Retrieve a list from secondary table using a composite key

Question

well, here I have an example of what I'm trying to do with no success. Sorry for the dummy example. I have the following tables:

CREATE TABLE HOUSE(
  HOUSE_NAME VARCHAR2(255),
  OWNER_ID VARCHAR2(255),
  PRIMARY KEY(FOLDER_NAME, USER_ID)
);

CREATE TABLE PET(
  HOUSE_NAME VARCHAR2(255) NOT NULL, 
  OWNER_ID VARCHAR2(255) NOT NULL,
  PET_NAME VARCHAR2(255) NOT NULL
);

ALTER TABLE PET
  ADD CONSTRAINT FK_PET_HOUSE
    FOREIGN KEY(HOUSE_NAME, OWNER_ID)
    REFERENCES HOUSE(HOUSE_NAME, OWNER_ID)
    ON DELETE CASCADE;

INSERT INTO HOUSE VALUES('House 1', 'Owner 1');
INSERT INTO HOUSE VALUES('House 2', 'Owner 1');
INSERT INTO HOUSE VALUES('House 3', 'Owner 1');

INSERT INTO PET VALUES('House 1', 'Owner 1', 'Dog');
INSERT INTO PET VALUES('House 1', 'Owner 1', 'Cat');
INSERT INTO PET VALUES('House 2', 'Owner 1', 'Duck');
INSERT INTO PET VALUES('House 3', 'Owner 1', 'Bird');

As you can see I'm using a composite key in my "HOUSE" table. What I want is to get from DB are 3 objects something like this:

Owner Id: Owner1
House name: House 1
Pets: [Dog, Cat]

Owner Id: Owner1
House name: House 2
Pets: [Duck]

Owner Id: Owner1
House name: House 3
Pets: [Bird]

I've been searching for a way to do it but I don't know how to link these tables to retrieve the list. What I have so far is:

@Entity
@Table(name="HOUSE")
@SecondaryTable(name="PET", pkJoinColumns={
        @PrimaryKeyJoinColumn(name="HOUSE_NAME", referencedColumnName="HOUSE_NAME"),
        @PrimaryKeyJoinColumn(name="OWNER_ID", referencedColumnName="OWNER_ID"),
})
public class HousePets implements Serializable {

    @Id
    @Column(name="HOUSE_NAME")
    private String houseName;

    @Id
    @Column(name="OWNER_ID")
    private String ownerId;

    @Column(table="PET" name="PET_NAME") //DON'T REALLY KNOW HOW TO DEAL WITH IT
    private Set<String> petsSet = new HashSet<String>

    //GETTERS AND SETTERS
}

And to retrieve the list I'm using a method something like this:

    public List<HousePets> getFoldersList() {
        em = emf.createEntityManager();
        Query q = em.createQuery("SELECT h FROM HousePets h WHERE h.ownerId = :ownerId");
        q.setParameter("ownerId", "Owner 1");
        List<HousePets> result = q.getResultList();
        return result;
    }

Thanks for your time!

Answer 1

Your model makes no sense. A SecondaryTable cannot be a OneToMany relation.

What you need is an OWNER table, that defines the OWNER_ID, (maybe a name, etc.)

Owner would have a OneToMany to Pet, and OneToOne (or ManyToOne, OneToMany?) to House

Pet would have a ManyToOne to Owner and ManyToOne to House

House would have a OneToMany to Pet and OneToMany? to Owner

To get an own, you would just select the owner, to get their pets you would just access them.