What is the correct way of accessing a Java Persistence unit from the web tier
(no EJB session beans)?
I use JBoss 4.2.0.
I can't get the resource injection annotations @PersistenceUnit or
@PersistenceContext to work, so I have done like this:
public class MyServletContextListener implements ServletContextListener {
|
| public void contextInitialized(ServletContextEvent sce) {
| try {
| EntityManagerFactory emf =
Persistence.createEntityManagerFactory("myunit");
|
sce.getServletContext().setAttribute(EntityManagerFactory.class.getName(), emf);
| }
| catch (RuntimeException e) {
| throw e;
| }
| catch (Exception e) {
| throw new RuntimeException(e);
| }
| }
|
| public void contextDestroyed(ServletContextEvent sce) {
| EntityManagerFactory emf =
(EntityManagerFactory)sce.getServletContext().getAttribute(
| EntityManagerFactory.class.getName());
| if (emf != null) {
| emf.close();
| }
| }
|
| }
|
and for each web request I do like this:
EntityManagerFactory emf =
(EntityManagerFactory)context.getAttribute(EntityManagerFactory.class.getName());
| EntityManager em = emf.createEntityManager();
| EntityTransaction transaction = em.getTransaction();
| transaction.begin();
|
| try {
| // process the request here...
| transaction.commit();
| } catch (Exception e) {
| transaction.rollback();
| // log the error
| } finally {
| em.close();
| }
|
It seems to work, but is it thread-safe and does it give reasonable
performance?
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