Can't get persistence to work in JBoss AS 7 ("Can't find a deployment unit named at subdeployment")

Question

I try to implement a demo that uses JBoss AS 7 with default hibernate and default Database shipped with JBoss AS. My implementation is similar to the "login" example from JBoss (I have some extra projects to implement a web service and deploy as EAR) and I can't catch the difference. Anyway I constantly get Runtime Exceptions such as

Caused by: java.lang.RuntimeException: Can't find a deployment unit named  at subdeployment "myproject.persistence.war" of deployment "myproject.ear"
    at org.jboss.as.weld.services.bootstrap.WeldJpaInjectionServices.getScopedPUName(WeldJpaInjectionServices.java:94) [jboss-as-weld-7.0.2.Final.jar:7.0.2.Final]
    at org.jboss.as.weld.services.bootstrap.WeldJpaInjectionServices.resolvePersistenceContext(WeldJpaInjectionServices.java:59) [jboss-as-weld-7.0.2.Final.jar:7.0.2.Final]
    at org.jboss.weld.util.Beans.injectEEFields(Beans.java:784) [weld-core-1.1.2.Final.jar:2011-07-26 15:02]

My MANIFEST.MF

Manifest-Version: 1.0
Dependencies: org.hibernate

My beans.xml is empty. In my lib folder I have the hibernate jars to have access to native hibernate features.

My persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">
    <persistence-unit name="accessControlDatabase">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source>
        <properties>
            <property name="hibernate.hbm2ddl.auto" value="create-drop" />
        </properties>
    </persistence-unit>
</persistence>  

And my two relevant classes:

import javax.enterprise.inject.Produces;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

public class Resources {
    @SuppressWarnings("unused")
    @Produces
    @PersistenceContext(name = "accessControlDatabase")
    private EntityManager em;
}

import java.util.List;

import javax.enterprise.context.RequestScoped;
import javax.inject.Inject;
import javax.inject.Named;
import javax.persistence.EntityManager;

import myproject.model.Session;
import myproject.model.User;

@Named("accessControlRepository")
@RequestScoped
public class AccessControlRepository {
    @Inject
    private EntityManager em;

    @SuppressWarnings("unchecked")
    public List<Session> getAllSessions() {
        return em.createQuery("from Session").getResultList();
    }
}

What can cause the exception? What should I look for to resolve the problem?

Answer 1

I have found a solution. I have to put the persistence.xml into the META-INF folder of the EAR project. If I do so I can use the @PersistenceContext annotation to get at the EntityManager. I think it should work the other way, too. This seems to be a workaround, not a real solution.