Spring, Hibernate and LazyInitializationExceptions

I’ve recently started using Spring for its comprehensive support for Hibernate 3. It makes writing DAOs a snap. There are a couple of wrinkles, however, one is the fact that lazy loading in Hibernate 3 is the default, combined with the fact that Spring will close the Hibernate Session automatically, giving you a LazyInitializationException when you try to access mapped fields from your persistent objects. The solution to this is the “Open Session In View” pattern, which Spring provide a ready-made filter for. Shown below is an extract from my PersistentTestCase, superclass, which all my DAO tests extend, and voila, no more Lazy Exceptions.



protected void setUp() throws ClassNotFoundException, SQLException {

      ClassPathXmlApplicationContext appContext = new ClassPathXmlApplicationContext("application_context.xml");

      factory = (BeanFactory) appContext;

      

      sessionFactory = (SessionFactory)factory.getBean("test.sessionFactory");

      Session s = sessionFactory.openSession();

      TransactionSynchronizationManager.bindResource(sessionFactory, new SessionHolder(s));  

  }

  

  protected void tearDown() {

     SessionHolder sessionHolder = (SessionHolder) TransactionSynchronizationManager.unbindResource(sessionFactory);

     SessionFactoryUtils.closeSessionIfNecessary(sessionHolder.getSession(), sessionFactory); 

  }

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