My scenario is that I don't want to do my entity manager interaction in a session bean - I want to use a layering approach that has Session beans <-> Business Delegates <-> DAOs <-> JPA entities. I'm getting frustrated that I cannot inject an entity manager into a DAO class inside the ejb container becasue it is not an EJB. I could use a jndi lookup, but then I jhave to worry about closing the entity manager. What I really want is to be able to access the EntityManager that was injected into the session bean that was my entry point to the container, but I do not want to pollute my BD and DAO API's with entity manager parameters. So, can I use ThreadLocal's? Do the folk at JBoss have a paradigm for doing this, or am I doing something completely stupid? The example code that follows is significantly trimmed. I've also left out the BD, and ignore the fact that a JPA entity is being returned to the client. I have a session bean with a simple getter method to load an entity. It delegates to a DAO | @Stateful | @Remote | public class StatefulColumnGroupServiceBean { | | @PersistenceContext(unitName="MyApp", type=PersistenceContextType.EXTENDED) | protected EntityManager em; | | public ColumnGroupEntity getColumnGroup(int iThreadNumber, long id) throws ServerException { | EntityManagerResource.getInstance().set(em); | ColumnGroupEntity cgvo = null; | try { | cgvo = ColumnGroupDAO.getInstance().getColumnGroup(id); | } | catch (DAOException e) { | log.error(e); | throw new ServerException( MessageFactory.getMessage("Bean.CannotFind", "ColumnGroup") + id, e ); | } | return cgvo; | } | } | The DAO is | public class ColumnGroupDAO { | | public ColumnGroupEntity getColumnGroup( long id ) throws DAOException { | EntityManager em = EntityManagerResource.getInstance().get(); | | ColumnGroupEntity res = null; | try { | res = em.find(ColumnGroupEntity.class, id); | } | catch (RuntimeException e) { | throw new DAOException(MessageFactory.getMessage("DAO.FindError", getClass().getName()) + id, e); | } | return res; | } | | | protected ColumnGroupDAO() { | } | | public static ColumnGroupDAO getInstance() { | if( instance == null ) { | synchronized( ColumnGroupDAO.class ) { | if( instance == null ) { | instance = new ColumnGroupDAO(); | } | } | } | return instance; | } | | private static ColumnGroupDAO instance = null; | | } | and the EntityManager is passed between bean and DAO by using a singleton ThreadLocal wrapping an EntityManager instance | public class EntityManagerResource extends ThreadLocalResource<EntityManager> { | | private static EntityManagerResource instance = null; | | public static EntityManagerResource getInstance( ) { | if( instance == null ) { | synchronized( EntityManagerResource.class ) { | if( instance == null ) { | instance = new EntityManagerResource( ); | } | } | } | return instance; | } | | protected EntityManagerResource() { | } | } | | public abstract class ThreadLocalResource<T> { | | private final ThreadLocal<T> resource = new ThreadLocal( ); | | public void set( T em ) { | resource.set(em); | } | | public T get( ) { | return resource.get(); | } | } | | Does this make sense? Any suggestions? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3984556#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...