In SpringTransactionFactory, the default release mode is on close. The default is changed to auto since hibernate 3.1, which is AFTER_TRANSACTION for jdbc transaction factory. Can any experts explains why onClose is better than afterTransaction in spring?

auto (the default) - this choice delegates to the release mode returned by the org.hibernate.transaction.TransactionFactory.getDe faultReleaseMode() method. For JTATransactionFactory, this returns ConnectionReleaseMode.AFTER_STATEMENT; for JDBCTransactionFactory, this returns ConnectionReleaseMode.AFTER_TRANSACTION. It is rarely a good idea to change this default behavior as failures due to the value of this setting tend to indicate bugs and/or invalid assumptions in user code.

http://hibernate.org/hib_docs/v3/ref...n-release.html

Code:
/**
 * Spring-aware implementation of the Hibernate TransactionFactory interface, aware of
 * Spring-synchronized transactions (in particular Spring-managed JTA transactions)
 * and asking for default release mode ON_CLOSE. Otherwise identical to Hibernate's
 * default {@link org.hibernate.transaction.JDBCTransactionFactory} implementation.
 *
 * @author Juergen Hoeller
 * @since 2.5.4
 * @see org.springframework.transaction.support.TransactionSynchronizationManager
 * @see org.hibernate.transaction.JDBCTransactionFactory
 */
public class SpringTransactionFactory implements TransactionFactory {

	/**
	 * Sets connection release mode "on_close" as default.
	 * <p>This was the case for Hibernate 3.0; Hibernate 3.1 changed
	 * it to "auto" (i.e. "after_statement" or "after_transaction").
	 * However, for Spring's resource management (in particular for
	 * HibernateTransactionManager), "on_close" is the better default.
	 */
	public ConnectionReleaseMode getDefaultReleaseMode() {
		return ConnectionReleaseMode.ON_CLOSE;
	}

	public Transaction createTransaction(JDBCContext jdbcContext, Context transactionContext) {
		return new JDBCTransaction(jdbcContext, transactionContext);
	}

	public void configure(Properties props) {
	}

	public boolean isTransactionManagerRequired() {
		return false;
	}

	public boolean areCallbacksLocalToHibernateTransactions() {
		return true;
	}

	public boolean isTransactionInProgress(
			JDBCContext jdbcContext, Context transactionContext, Transaction transaction) {

		return (transaction != null && transaction.isActive()) ||
				TransactionSynchronizationManager.isActualTransactionActive();
	}

}