I've just migrated from Tomcat to JBoss AS 7. So, I configured Mysql datasource in JBoss (adding module.xml with associated Jar, adding driver bloc into standalone.xml and configuring datasource through JBoss interface. No errors when deploying but impossible to get an entityManager (JPA with Hibernate in background). Indeed, when this code is executed: Persistence.createEntityManagerFactory("RoomManagement"); I obtain this error : > javax.persistence.PersistenceException: No Persistence provider for > EntityManager named RoomManagement > javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:69) > javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47) Very strange because I well verified that my persistence.xml does take place into War at WEB-INF/classes/META-INF directory. My persistence.xml looks like as follow : org.hibernate.ejb.HibernatePersistence java:jboss/datasources/MySqlDS com.parisdescartes.roommanagement.domain.entities.Address com.parisdescartes.roommanagement.domain.entities.Building com.parisdescartes.roommanagement.domain.entities.Civility com.parisdescartes.roommanagement.domain.entities.EventType com.parisdescartes.roommanagement.domain.entities.Job com.parisdescartes.roommanagement.domain.entities.Reservation com.parisdescartes.roommanagement.domain.entities.Room com.parisdescartes.roommanagement.domain.entities.RoomType com.parisdescartes.roommanagement.domain.entities.Tool com.parisdescartes.roommanagement.domain.entities.User com.parisdescartes.roommanagement.domain.entities.UserDetail com.parisdescartes.roommanagement.domain.entities.Schedule Did I make a mistake or forgot to specify something ?