Greetings,
The key is in 'CMP' - "Container Managed Persistence". What this means is that the container is managing (performing the work of) synchronization between the data resource and the bean's state fields (those, at least, which map to the resource ;), including the primary key field(s). IOW, the container creates the instance of the Primary Key class, so there is no reason for the bean class to do so.
Regards,
Tony "Vee Schade" Cook