javax.el.PropertyNotFoundException: Target Unreachable, 'null' returned null adf 12.2.1.4
Either #{userController} or #{userController.users} is null.
My cents that #{userController.users} is null. You aren't prepopulating it in your bean. The #{userController} is correctly declared and used as @ManagedBean.
You need to prepopulate it in the postconstruct of the bean:
@PostConstruct
public void init() {
users = new Iuser();
}