Free web hosting services - Bulk and batch operations Another option that completely
Bulk and batch operations Another option that completely avoids memory consumption of the persistence context (by effectively disabling it) is the StatelessSession interface. 12.2.3 Using a stateless Session The persistence context is an essential feature of the Hibernate and Java Persistence engine. Without a persistence context, you wouldn t be able to manipulate object state and have Hibernate detect your changes automatically. Many other things also wouldn t be possible. However, Hibernate offers you an alternative interface, if you prefer to work with your database by executing statements. This statement-oriented interface, org.hibernate.StatelessSession, feels and works like plain JDBC, except that you get the benefit from mapped persistent classes and Hibernate s database portability. Imagine that you want to execute the same update all item objects procedure you wrote in an earlier example with this interface: Session session = sessionFactory.openStatelessSession(); Transaction tx = session.beginTransaction(); ScrollableResults itemCursor = session.createQuery(”from Item”).scroll(); while ( itemCursor.next() ) { Item item = (Item) itemCursor.get(0); modifyItem(item); session.update(item); } tx.commit(); session.close(); The batching is gone in this example you open a StatelessSession. You no longer work with objects in persistent state; everything that is returned from the database is in detached state. Hence, after modifying an Item object, you need to call update() to make your changes permanent. Note that this call no longer reattaches the detached and modified item. It executes an immediate SQL UPDATE; the item is again in detached state after the command. Disabling the persistence context and working with the StatelessSession interface has some other serious consequences and conceptual limitations (at least, if you compare it to a regular Session): A StatelessSession doesn t have a persistence context cache and doesn t interact with any other second-level or query cache. Everything you do results in immediate SQL operations.
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