In addition to using the wrong persistence unit name in createEntityManagerFactory, the servlet has:
@PersistenceUnit
private EntityManagerFactory emf ;
This looks like you are attempting to unject the EMF, which you shouldn't do if using a resource local persistence unit. This annotation could be causing the server to load a default persistence unit for your entity classes, which would have a default datasource. Try removing this annotation, ensuring that you only have the one persistence.xml file and that you are using the correct persistence unit name.
Best Regards,
Chris
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