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POThe mystery of Java EE 6 annotations inheritance
 

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    <p>I'm using inheritance with EJB in a few scenarios, sometimes with annotations in the super class like this generic entityDAO:</p> <pre><code>public class JpaDAO&lt;T&gt;{ protected Class&lt;T&gt; entityClass; @PersistenceContext(unitName="CarrierPortalPU") protected EntityManager em; protected CriteriaBuilder cb; @PostConstruct private void init() { cb = em.getCriteriaBuilder(); } public JpaDAO(Class&lt;T&gt; type) { entityClass = type; } @TransactionAttribute(TransactionAttributeType.REQUIRED) public void create(T entity) { em.persist(entity); } @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED) public T find(Object id) { return em.find(entityClass, id); } @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED) public List&lt;T&gt; findAll(){ CriteriaQuery&lt;T&gt; cq = cb.createQuery(entityClass); Root&lt;T&gt; entity = cq.from(entityClass); cq.select(entity); return em.createQuery(cq).getResultList(); } @TransactionAttribute(TransactionAttributeType.REQUIRED) public void remove(T entity) { em.remove(em.merge(entity)); } @TransactionAttribute(TransactionAttributeType.REQUIRED) public T edit(T entity) { return em.merge(entity); } } </code></pre> <p>With an example subclass implemented like this:</p> <pre><code>@Stateless @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED) public class DepartmentDAO extends JpaDAO&lt;Department&gt; { public DepartmentDAO() { super(Department.class); } public Department findByName(String name){ CriteriaQuery&lt;Department&gt; cq = cb.createQuery(Department.class); Root&lt;Department&gt; department = cq.from(Department.class); cq.where(cb.equal(department.get(Department_.name), name)); cq.select(department); try{ return em.createQuery(cq).getSingleResult(); }catch(Exception e){ return null; } } } </code></pre> <p>I recently read that java annotations are NOT inherited <a href="http://fusionsoft-online.com/articles-java-annotations.php" rel="noreferrer">(source)</a>. This should cause my JpaDAO to throw a null pointer exception when accessing its entitymanager or its criteriabuilder (since both @PersistanceContext and @PostConstruct would be ignored), however this it not the case. Can someone clarify how this really works? I am abit worried about what happens to my @TransactionAttributes in the superclass, can I trust a REQUIRED to actually use transactions when called from the subclass, when the subclass has NOT_SUPPORTED as class default?</p>
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