Domain classes generated by Forge need to override hashCode/equals if they are to be useful in a UI (among other places). This is hard to do if we know nothing about the semantics of the class, but the PersistencePlugin does know something: namely, the Id.

The following implementation would suffice for my purposes:

@Override
public boolean equals(Object that) {

if (this == that)

{ return true; }

if (that == null)

{ return false; }

if (getClass() != that.getClass()) { return false; }

if (id != null)

{ return id.equals(((Employer) that).id); }

return super.equals(that);
}

@Override
public int hashCode() {

if (id != null)

{ return id.hashCode(); }

return super.hashCode();
}

But I'm happy for other implementations too.