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POAddding a persistence unit in JNDI for EJB modules
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  1. POAddding a persistence unit in JNDI for EJB modules
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    copied!<p>I am working on a simple EJB module using sample code. I am trying to implement CURD operations through a SOAP web service. I have a persistence unit defined in <code>persistence.xml</code>.</p> <p>Here is the code for my implementation. The problem is that I cannot create an instance of <code>PersistenceService</code> because the persistence unit name is not present in the JNDI listings.</p> <p>If, instead of using code injection, I use</p> <pre><code>EntityManagerFactory emf = Persistence.createEntityManagerFactory(PU_NAME); em = emf.createEntityManager(); </code></pre> <p>the code runs, but then the transaction is managed by the container. I was reading through some tutorials and they mentioned that, in this scenario, if the user wants to roll the transaction back later, he cannot do so.</p> <p>What can I do instead?</p> <h3>users class</h3> <pre><code>@WebService() @Stateless() public class users { public users() { } /** * Web service operation */ @WebMethod(operationName = "addUser") public Integer addUser( @WebParam(name = "UserName") final String UserName, @WebParam(name = "LastName") final String LastName) { DatabaseEntityManager dem = new DatabaseEntityManager(); Integer result = null; try { result = dem.addUser(UserName, LastName, false); dem.commitTx(); return result; } catch(Exception E) { } return new Integer(-1); } </code></pre> <h3>DatabaseEntityManager class</h3> <pre><code>public class DatabaseEntityManager { PersistenceService ps_bck = null; public DatabaseEntityManager() { } public SiteUsers addUser( String Username, String LastName, boolean commit) throws Exception { AppUser appUser = new appUser(UserName, LastName); //AppUser is an entity class PersistenceService ps = PersistenceService.getInstance(); try { ps.beginTx(); EntityManager em = ps.getEntityManager(); em.persist(appUser); if (commit) ps.commitTx(); else ps_bck = ps; } catch (Exception E) { ps.rollbackTx(); } finally { ps.close(); } return appUser.getId(); } void commitTx() throws Exception { try { ps_bck.commitTx(); } catch(Exception E) { throw E; } finally { ps_bck =null; } } } </code></pre> <h3>PersistenceService class &#8212; borrowed from sample code generated by NetBeans</h3> <pre><code>public class PersistenceService { private static String DEFAULT_PU = "pers-ejbPU"; private static ThreadLocal&lt;PersistenceService&gt; instance = new ThreadLocal&lt;PersistenceService&gt;() { @Override protected PersistenceService initialValue() { return new PersistenceService(); } }; private EntityManager em; private UserTransaction utx; private PersistenceService() { try { //This code runs // EntityManagerFactory emf = ersistence.createEntityManagerFactory(DEFAULT_PU); // em = emf.createEntityManager(); //This code throws an exception this.em = (EntityManager) new InitialContext().lookup("java:comp/env/persistence/"+ DEFAULT_PU); this.utx = (UserTransaction) new InitialContext().lookup("java:comp/UserTransaction"); } catch (NamingException ex) { throw new RuntimeException(ex); } } /** * Returns an instance of PersistenceService. * * @return an instance of PersistenceService */ public static PersistenceService getInstance() { return instance.get(); } private static void removeInstance() { instance.remove(); } /** * Returns an instance of EntityManager. * * @return an instance of EntityManager */ public EntityManager getEntityManager() { return em; } /** * Begins a resource transaction. */ public void beginTx() { try { utx.begin(); em.joinTransaction(); } catch (Exception ex) { throw new RuntimeException(ex); } } /** * Commits a resource transaction. */ public void commitTx() { try { utx.commit(); } catch (Exception ex) { throw new RuntimeException(ex); } } /** * Rolls back a resource transaction. */ public void rollbackTx() { try { utx.rollback(); } catch (Exception ex) { throw new RuntimeException(ex); } } /** * Closes this instance. */ public void close() { removeInstance(); } } </code></pre>
 

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