JDBCContext

成员变量

owner:session
connectionManager:管理连接
isTransactionCallbackRegistered:是否注册回调
hibernateTransaction:JTATransaction或CMTTransaction事例

重要方法

borrowConnection由session.connection调用
public Connection borrowConnection() {
		return connectionManager.borrowConnection();
	}

connection由JDBCTransaction在事务开始或完成时调用   
public Connection connection() throws HibernateException {
		if ( owner.isClosed() ) {
			throw new SessionException( "Session is closed" );
		}

		return connectionManager.getConnection();
	}

registerCallbackIfNecessary和registerSynchronizationIfPossible  注册同步
  JDBCTransaction: 本地同步
  JTATransaction：寻找javax.trasaction.TransactionManager和激活着的JTA事务，如果满足注册JTA同步，否则调用registerCallbackIfNecessary以支持本地同步
  CMTTransaction:寻找javax.trasaction.TransactionManager和激活着的JTA事务
，如果不满足则抛错即CMT不支持本地同步
	public boolean registerCallbackIfNecessary() {
		if ( isTransactionCallbackRegistered ) {
			return false;
		}
		else {
			isTransactionCallbackRegistered = true;
			return true;
		}

	}
public boolean registerSynchronizationIfPossible() {
		if ( isTransactionCallbackRegistered ) {
			// we already have a callback registered; either a local
			// (org.hibernate.Transaction) transaction has accepted
			// callback responsibilities, or we have previously
			// registered a transaction synch.
			return true;
		}
		boolean localCallbacksOnly = owner.getFactory().getSettings()
				.getTransactionFactory()
				.areCallbacksLocalToHibernateTransactions();
		if ( localCallbacksOnly ) {
			// the configured transaction-factory says it only supports
			// local callback mode, so no sense attempting to register a
			// JTA Synchronization
			return false;
		}
		TransactionManager tm = owner.getFactory().getTransactionManager();
		if ( tm == null ) {
			// if there is no TM configured, we will not be able to access
			// the javax.transaction.Transaction object in order to
			// register a synch anyway.
			return false;
		}
		else {
			try {
				if ( !isTransactionInProgress() ) {
					log.trace( "TransactionFactory reported no active transaction; Synchronization not registered" );
					return false;
				}
				else {
					javax.transaction.Transaction tx = tm.getTransaction();
					if ( JTAHelper.isMarkedForRollback( tx ) ) {
						// transactions marked for rollback-only cause some TM impls to throw exceptions
						log.debug( "Transaction is marked for rollback; skipping Synchronization registration" );
						return false;
					}
					else {
						if ( hibernateTransaction == null ) {
							hibernateTransaction = owner.getFactory().getSettings().getTransactionFactory().createTransaction( this, owner );
						}
						tx.registerSynchronization( new CacheSynchronization(owner, this, tx, hibernateTransaction) );
						isTransactionCallbackRegistered = true;
						log.debug("successfully registered Synchronization");
						return true;
					}
				}
			}
			catch( HibernateException e ) {
				throw e;
			}
			catch (Exception e) {
				throw new TransactionException( "could not register synchronization with JTA TransactionManager", e );
			}
		}
	}

判断事务是否激活状态
public boolean isTransactionInProgress() {
		return owner.getFactory().getSettings().getTransactionFactory()
				.isTransactionInProgress( this, owner, hibernateTransaction );
	}

只要本地同步或JTA同步执行已注册，在事务完成之后
如果没有注册，则session.close、session.disconnect进行资源清理时调用
public void afterTransactionCompletion(boolean success, Transaction tx) {
		log.trace( "after transaction completion" );

		if ( getFactory().getStatistics().isStatisticsEnabled() ) {
			getFactory().getStatisticsImplementor().endTransaction(success);
		}

		connectionManager.afterTransaction();

		isTransactionCallbackRegistered = false;
		hibernateTransaction = null;
		owner.afterTransactionCompletion(success, tx);
	}

afterNontransactionalQuery(名字取得不好)非事务操作:在每条语句执行后判断isTransactionInProgress==false时执行
/**
	 * Called after executing a query outside the scope of
	 * a Hibernate or JTA transaction
	 */
	public void afterNontransactionalQuery(boolean success) {
		log.trace( "after autocommit" );
		try {
			// check to see if the connection is in auto-commit 
			// mode (no connection means aggressive connection
			// release outside a JTA transaction context, so MUST
			// be autocommit mode)
			boolean isAutocommit = connectionManager.isAutoCommit();

			connectionManager.afterTransaction();
			
			if ( isAutocommit ) {
				owner.afterTransactionCompletion(success, null);
			}
		}
		catch (SQLException sqle) {
			throw JDBCExceptionHelper.convert( 
					owner.getFactory().getSQLExceptionConverter(),
					sqle,
					"could not inspect JDBC autocommit mode"
				);
		}
	}