JPA OneToMany mapping whit toplink...

Question

I have a problem when i want to map a OneToMany unidirectional relation using toplink. Toplink maps the relation as a ManyToMany relation instead?
Code in a class called Car:
@OneToMany(cascade={CascadeType.PERSIST, CascadeType.REMOVE})
public List<Wheel> getWheels() { return wheels; }
public void setWheels(List<Wheel> wheels) { this.wheels = wheels; }
toplink output:
[TopLink Config]: 2006.11.07 11:41:41.984--ServerSession(9505840)--The target entity (reference) class for the one to many mapping element [public java.util.List entities.Car.getWheels()] is being defaulted to: class entities.Wheel.
[TopLink Config]: 2006.11.07 11:41:41.984--ServerSession(9505840)--The join table name for the many to many mapping [public java.util.List entities.Car.getWheels()] is being defaulted to: CAR_WHEEL.
[TopLink Config]: 2006.11.07 11:41:41.984--ServerSession(9505840)--The source primary key column name for the many to many mapping [public java.util.List entities.Car.getWheels()] is being defaulted to: CARID.
[TopLink Config]: 2006.11.07 11:41:41.984--ServerSession(9505840)--The source foreign key column name for the many to many mapping [public java.util.List entities.Car.getWheels()] is being defaulted to: Car_CARID.
[TopLink Config]: 2006.11.07 11:41:41.984--ServerSession(9505840)--The target primary key column name for the many to many mapping [public java.util.List entities.Car.getWheels()] is being defaulted to: WHEELID.
[TopLink Config]: 2006.11.07 11:41:41.984--ServerSession(9505840)--The target foreign key column name for the many to many mapping [public java.util.List entities.Car.getWheels()] is being defaulted to: wheels_WHEELID.
When i use @JoinColumn i get a message from toplink that says that it is not required when the relation is unidirectional so it is not possible to identify the foreign key..

Answer 1

The JPA Spec does not allow unidirectional 1-m relationships without using a join table, they must always be bidirectional. You must define a 1-1 back-reference and use the "mapped-by" in the 1-m mapping referencing the 1-1.