Trying to see if adding class tag in persistence.xml helps to
resolve the error - java.lang.IllegalStateException: Unable to
retrieve EntityManagerFactory for unitName AffableBeanPU
Testing - Replaced public List<T> findAll() with dummy code to see if it
removes a previous exception. java.lang.IllegalStateException: Unable to retrieve EntityManagerFactory for unitName AffableBeanPU.

New exception is -

javax.servlet.ServletException: Servlet.init() for servlet ControllerServlet threw exception

root cause
javax.ejb.EJBAccessException

root cause
javax.ejb.AccessLocalException: Client not authorized for this invocation