Photography web hosting - Conversations with JPA Don t forget that em.flush() must
Conversations with JPA Don t forget that em.flush() must be called manually, in the last transaction in the third event otherwise no modifications are made persistent: public static class ManageAuctionExtended { … public Item endAuction(Item item) { EntityTransaction tx = em.getTransaction(); tx.begin(); // Merge item … // Set winning bid … em.flush(); // Commit the conversation tx.commit(); return mergedItem; } } The official architectural solution relies on nontransactional behavior. Instead of a simple FlushMode setting, you need to code your data-access operations without transaction boundaries. One of the reasons given by expert group members about the missing FlushMode is that a transaction commit should make all modifications permanent. So, you can only disable flushing for the second step in the conversation by removing transaction demarcation: public class ManageAuction { … public boolean sellerHasEnoughMoney(User seller) { boolean sellerCanAffordIt = (Boolean) em.createQuery(”select …”).getSingleResult(); return sellerCanAffordIt; } … } This code doesn t trigger a flush of the persistence context, because the Entity- Manager is used outside of any transaction boundaries. The EntityManager that executes this query is now working in autocommit mode, with all the interesting consequences we covered earlier in section 10.3, Nontransactional data access. Even worse, you lose the ability to have repeatable reads: If the same query is executed twice, the two queries each execute on their own database connection in autocommit mode. They can return different results, so the database transaction isolation levels repeatable read and serializable have no effect. In other words, with
Note: In case you are looking for affordable and reliable webhost to host and run your j2ee application check Vision J2ee Web Hosting services.