Null in SessionImpl accessing entityManager in an abstract class

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The title says it all. I am getting a null pointer when accessing an entity manager from an abstract class. I have an abstract class where I inject an entityManager

@In
private EntityManager entityManager;

I have a getter in this class to expose the entity manager to subclasses. I can call the getter in my concrete class and make use of the entity manager. However when call a function on the abstract class which makes use of the same entity manager I get an NPE

java.lang.NullPointerException
at org.hibernate.impl.SessionImpl.get(SessionImpl.java:835)
at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:182)
at org.jboss.seam.persistence.EntityManagerProxy.find(EntityManagerProxy.java:87)
at com.swarm.service.AbstractEntityService.findById(AbstractEntityService.java:22)

I am guessing this has something to to with how sessions are opened and closed by the proxy. Any help on this would be great.