Version with xref tables

Question

We are using optimistic locking using a version number on various tables. We have a situation where we using xref tables as follows.
user object mapped to USER table.
team object mapped to TEAM table.
a team has users and a user is on teams.
This is represented as a many-to-many mapping using a XREF table that has a userID and a teamID.
The problem is that I want to ensure integrity across multiple users adding and removing users from and to a team.
We use optimistic locking on the USER and TEAM tables.
Versioning is not enforced when using the XREF table.
How best might this be handled. So that one user does't overlay the addition or removeal of users by another user.
Thanks
Mark

Answer 1

Marc,
The easiest way to do this is to have TopLink force or check the optimistic lock values on the User and Team instances that are involved in the new relationship. Here is a simple code sample from the employee example that forces an employee's optimistic lock field to be incremented when a project is added:
public void forceOptimisticLockUpdateExample() {
Employee emp = (Employee) getSession().readObject(Employee.class);
UnitOfWork uow = getSession().acquireUnitOfWork();
Employee empWC = (Employee) uow.registerObject(emp);
SmallProject newProj = (SmallProject) uow.registerObject(new SmallProject());
newProj.setName("New");
newProj.setDescription("Example of forcing optimistic lock increment");
empWC.addProject(newProj);
uow.forceUpdateToVersionField(empWC, true); // False would mean just check the value
uow.commit();
Doug