Hello, I'm using Jboss-4.0.5-GA in the ejb3 configuration. I'm trying to implement the following entities and relationships, without success: Entity: Security Entity: Trade Entity: Allocation extends Trade Security->Trade is one-to-many with Trade as the relationship owner Trade->Security is many-to-one Security->Allocation is one-to-one with Allocation as the relationship owner Allocation->Security is one-to-one The basic idea is that while a Security may have a collection of Trades associated with it, at most one can be an Allocation. And if a Security has an associated Allocation, then that Allocation must appear in the Trades collection of the Security as well. I've tried this approach: @Entity public class Security { ... @OneToMany(mappedBy="security") public Collection<Trade> getTrades() {...} @OneToOne(mappedBy="security") public Allocation getAllocation() {...} } @Entity public abstract class Trade { ... @ManyToOne public Security getSecurity() {...} } @Entity public class Allocation extends Trade {...} When I try to update (merge) an Allocation, the query and error I get from Hibernate look like this: Query: [org.hibernate.SQL] select allocation0_.id as id9_10_, etc., ... where allocation0_.security_id=? and allocation0_.DTYPE='alloc' Error: [org.hibernate.type.LongType] could not bind value '1st Lien Term Loan' to parameter: 1; com.xyz.entity.Security In the error message, '1st Lien Term Loan' is the toString() value of the associated Security, not it's long getId() value, as I would have expected. I have also tried giving the one-to-one a different name on the owner side: @Entity public class Security { ... @OneToMany(mappedBy="security") public Collection<Trade> getTrades() {...} @OneToOne(mappedBy="issue") public Allocation getAllocation() {...} } @Entity public abstract class Trade { ... @ManyToOne public Security getSecurity() {...} } @Entity public class Allocation extends Trade { ... @OneToOne public Security getIssue() { return super.getSecurity(); } } But the result is the same. Does anyone know what the problem is here, or am I using the wrong approach? Any pointers would be much appreciated. Thanks, wmathews(a)aladdincapital.com