Nontransactional data access tion isn t (Affordable web design) already in that
Nontransactional data access tion isn t already in that mode. The previous code examples now work predictably, and the JDBC driver wraps a short transaction around every SQL statement that is send to the database with the implications we listed earlier. In which scenarios would you enable the autocommit mode in Hibernate, so that you can use a Session without beginning and ending a transaction manually? Systems that benefit from autocommit mode are systems that require on-demand (lazy) loading of data, in a particular Session and persistence context, but in which it is difficult to wrap transaction boundaries around all code that might trigger on-demand data retrieval. This is usually not the case in web applications that follow the design patterns we discuss in chapter 16. On the other hand, desktop applications that access the database tier through Hibernate often require on-demand loading without explicit transaction boundaries. For example, if you double-click on a node in a Java Swing tree view, all children of that node have to be loaded from the database. You’d have to wrap a transaction around this event manually; the autocommit mode is a more convenient solution. (Note that we are not proposing to open and close Sessions on demand!) 10.3.3 Optional transactions with JTA The previous discussion focused on autocommit mode and nontransactional data access in an application that utilizes unmanaged JDBC connections, where Hibernate manages the connection pool. Now imagine that you want to use Hibernate in a Java EE environment, with JTA and probably also CMT. The connection. autocommit configuration option has no effect in this environment. Whether autocommit is used depends on your transaction assembly. Imagine that you have an EJB session bean that marks a particular method as nontransactional: @Stateless public class ItemFinder { @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED) public Item findItemById(Long id) { Session s = getSessionFactory().openSession(); Item item = (Item) s.get(Item.class, id); s.close(); return item; } } The findItemById() method produces an immediate SQL SELECT that returns the Item instance. Because the method is marked as not supporting a transaction context, no transaction is started for this operation, and any existing transaction
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