I'm trying to convert my old Hibernate GenericDAO to an EJB3.0 GenericDAO. My
problem is that EJB3.0 requires a specific Query to retrieve all objects rather
then a Criterion (like Hibernate) that is purely defined by a class type.
Hibernate could do it like this:
| protected List<I>
| findAll()
| throws DAOException
| {
| List<I> myList;
|
| try
| {
| Criteria aCriteria =
| getSession().createCriteria(I);
| myList = aCriteria.list();
| }
| catch(HibernateException anException)
| {
| throw new DAOException(anException);
| }
| catch(Exception anException)
| {
| throw new DAOException(anException);
| }
|
| return myList;
| }
|
My question is: Can the EntityManager (or some other service object) use
something other then a query to obtain all objects from a table?
| public abstract class
| GenericEJBDAO<I, T, ID>
| implements GenericDAO<I, ID>
| {
| //--------------------------------------------------------------------
| // Constructors
| //--------------------------------------------------------------------
|
| protected GenericEJBDAO(Class<I> aPersistanceInterface,
| Class<T> aPersistanceClass)
| {
| thePersistanceInterface = aPersistanceInterface;
| thePersistanceClass = aPersistanceClass;
| }
|
| //--------------------------------------------------------------------
| // Public methods
| //--------------------------------------------------------------------
|
| public Collection<T>
| findAll()
| throws DAOException
| {
| try
| {
| ...?
| }
| catch(Exception anException)
| {
| throw new DAOException(anException);
| }
| }
|
| public I
| findByID (ID anID)
| throws DAOException
| {
| if(anID == null)
| throw new IllegalArgumentException("ID cannot be null");
|
| Object myPersistantObject = theManager.find(thePersistanceClass,
anID);
| return thePersistanceInterface.cast(myPersistantObject);
| }
|
| public void
| delete(ID anID)
| throws DAOException
| {
| if(anID == null)
| throw new IllegalArgumentException("ID cannot be null");
|
| Object myPersistantObject = theManager.find(thePersistanceClass,
anID);
| theManager.remove(myPersistantObject);
| }
|
| //--------------------------------------------------------------------
| // Members
| //--------------------------------------------------------------------
|
| @PersistenceContext
| protected EntityManager theManager;
|
| private Class<T> thePersistanceClass;
|
| private Class<I> thePersistanceInterface;
|
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