Hibernate adding/overwriting records incorrectly

I am a HIbernbate newbie and have a problem that has been bothering me for days. Here is a rundown of the issue I am having:

1. There is a @Entity class called Resource which contains a Key field and an ID field.
2. There is a @Entity class called Agreement which extends Resource.
3. There is a @Entity class called Schedule which extends Resource and contains an Agreement field.
4. There is a @Entity class called AgreementProperty.
5. There is a @Entity class called PositionAgreementProperty which extends AgreementProperty.
6. There is a @Entity class called ShiftAgreementProperty which extends AgreementProperty.
7. Agreement has a field which is a List of PositionAgreementProperty classes.
8. Agreement has a field which is a List of ShiftAgreementProperty classes.
9. When I add an Agreement via the web page, Hibernate populates:
a. the Agreement table with one record that contains nothing but an agreement_key of 1
b. the Resource table with one record, including the agreement_key and a generated ID
c. the AgreementProperty table with 5 records containing keys 1 - 5.
d. the PositionAgreementProperty table that contains the agreement_key (always set to 1) and the 1, 2, 3 AgreementProperty keys
e. the ShiftAgreementProperty table that contains the agreement_key (always set to 1) and the 4, 5 AgreementProperty keys
10. When I then add a Schedule via the web page, which includes the name of the Agreement from the database, Hibernate populates:
a. the Agreement table with new record with an agreement_key of 2.
b. the Resource table with a new record with an agreement_key of 2 and a generated ID of NULL
c. the Resource table with a second new record for the Schedule.
11. The PositionAgreementProperty and ShiftAgreementProperty tables have their agreement_key fields updated from 1 to 2, for the "new" Agreement.
12. Now Agreement 1 does not have any PositionAgreementProperty nor ShiftAgreementProperty records associated with it.

What I am trying to figure out is:
1. Can I prevent a new Agreement from being added and just use the previous agreement_key
a. I think Hibernate does this because both Agreement and Schedule get their key values by inheriting from Resource
2. If not, can I make Hibernate insert new AgreementProperty records instead of updating the existing ones?

The following are the class definitions (with the getters and setters removed for the sake of brevity):

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@XmlRootElement
public class Resource implements Serializable {
@Id
@Column(name = "_key")
@GeneratedValue
@XmlTransient
private Long key;

@Column(unique = true)
@XmlTransient
private String id;
}

@Entity
@XmlRootElement
public class Agreement extends Resource {
@JoinColumn(name = "agreement__key", referencedColumnName = "_key")
@OneToMany(cascade = CascadeType.ALL)
private List<PositionAgreementProperty> positionProperties = new ArrayList<PositionAgreementProperty>();

@JoinColumn(name = "agreement__key", referencedColumnName = "_key")
@OneToMany(cascade = CascadeType.ALL)
private List<ShiftAgreementProperty> shiftProperties = new ArrayList<ShiftAgreementProperty>();
}

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@XmlRootElement
public class AgreementProperty implements Serializable {
@Id
@Column(name = "_key")
@GeneratedValue
@XmlTransient
private Long key;
}

@Entity
@XmlRootElement
public class PositionAgreementProperty extends AgreementProperty {
public PositionAgreementProperty() {
super();
}
}

@Entity
@XmlRootElement
public class ShiftAgreementProperty extends AgreementProperty {
public ShiftAgreementProperty() {
super();
}
}

@Entity
@XmlRootElement
public class Rotation extends Resource {
}

@Entity
@XmlRootElement
public class Schedule extends Rotation {
@OneToOne(cascade = CascadeType.ALL)
private Agreement agreement;
}


Any help offered would be appreciated. I am not sure what kind of code examples I should include besides the class declarations since the code doing the "work" was generated via Google Guice. Thanks.

I suspect this is all about how you are working with these objects.
Taking question 1, how do you add a Schedule? Specifically how do you add the existing Agreement to the Schedule?

The Agreement is being added to the schedule using the Schedule setter function and then the Schedule object is written to the database using javax.persistence.EntityManager.persist.

Are you sure it's the existing Agreement?
And simply describing the situation really isn't the best way of handling this.
Some code would make life a lot easier.

The Agreement is added on a separate page, and then when the Schedule is added, the name of all Agreements in the database are listed in a drop down box and the user chooses one. The code adding them is:

@Override
public String add(final R resource) {
final Query query = entityManager.createQuery("from Resource where id = :id");

String id;
Resource existing;

query.setMaxResults(1);

do {
id = identifier.identify(resource);
existing = get(entityManager, Resource.class, id);
} while (existing != null && identifier.collision(id, existing, resource));

if (existing == null) {
resource.setId(id);
entityManager.getTransaction().begin();
onBeforePersist(id, resource);
entityManager.persist(resource);
onAfterPersist(id, resource);
entityManager.getTransaction().commit();

return id;
}

return null;
}

So when a Schedule is created there is no Agreement?
That works OK?

I can make neither head nor tail of that above code...it's far too generic compared to the problem you are describing.

It is inherited code made using Google Guice. I have trouble making sense of it too,

However, before I added the AgreementPropety class, the code worked, although not very efficiently. Which is why I believe it has something to do with how the classes are declared.

BTW, the Schedule is added to the database, but the Agreement is added a second time and the AgreementProperty entires are overwritten with the new Agreement key.

I fear I would be as lost as you then.
Never used Guice, so I can't say one way or the other.