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POIs my @produced EntityManager thread safe in a servlet container?
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copied!<p>In a project of mine I'm trying to switch management of my persistence from application to container. I'm following these instructions: <a href="http://docs.oracle.com/javaee/6/tutorial/doc/gkhrg.html" rel="nofollow">http://docs.oracle.com/javaee/6/tutorial/doc/gkhrg.html</a></p> <p>I've read about EntityManager not being thread safe and just want to make sure that my setup is correct. My concern: <a href="http://weblogs.java.net/blog/2005/12/19/dont-use-persistencecontext-web-app" rel="nofollow">http://weblogs.java.net/blog/2005/12/19/dont-use-persistencecontext-web-app</a>. </p> <p>I have a class that produces a persistence context.</p> <pre><code>@Singleton public class JpaResourceProducer { //The "pu" unit is defined with transaction-type="JTA" @Produces @PersistenceUnit(unitName = "pu") @Database EntityManagerFactory databasePersistenceUnit; @Produces @PersistenceContext(unitName = "pu") @Database EntityManager databaseEntityManager; /* Alternative @PersistenceContext(unitName = "pu") private EntityManager em; @Produces @UserDatabase public EntityManager create() { return em; } public void close(@Disposes @Database EntityManager em) { em.close(); } */ } </code></pre> <p>Then I have a jax-rs resource that injects a DAO.</p> <pre><code>@RequestScoped @Path("/endpoint") public class MyResource { @Inject private Dao dao; @GET @Produces({MediaType.APPLICATION_JSON}) public Converter get() { MyEntity entity = dao.find(1); Converter converter = new Converter(entity); return converter; } } </code></pre> <p>And finally a <code>DAO</code> where I inject the <code>EntityManager</code>.</p> <pre><code>@Singleton public class JpaDao<T, K extends Serializable> implements Dao<T, K> { protected Class<T> entityClass; @Inject @Database EntityManager em; public JpaDao() { ParameterizedType genericSuperclass = (ParameterizedType) getClass().getGenericSuperclass(); this.entityClass = (Class<T>) genericSuperclass.getActualTypeArguments()[0]; } public T find(K id) { return em.find(entityClass, id); } .... } </code></pre> <p><em><strong>1. Is this a good setup in terms of thread safety and overall performance?</em></strong></p> <hr> <p>Bonus questions:</p> <p>In the <code>JpaResourceProducer</code> I have an alternative setup for the <code>EntityManager</code> where I manually close the manager on dispose. </p> <p><em><strong>2. Is the container handling close of my <code>EntityManager</code> automatically?</em></strong></p> <p>The example from Oracle includes an <code>EntityManagerFactory</code>. </p> <p><em><strong>3. Do I really need an <code>EntityManagerFactory</code> when I'm using CMP?</em></strong></p>

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