Spring具体事务处理器的实现

Spring提供两种方式的编程式事务管理，分别是：使用TransactionTemplate和直接使用PlatformTransactionManager。

一.使用TransactionTemplate
1.TransactionTempale采用和其他Spring模板，如JdbcTempalte和HibernateTemplate一样的方法。它使用回调方法，把应用程序从处理取得和释放资源中解脱出来。如同其他模板，TransactionTemplate是线程安全的。代码片段：

public Object execute(TransactionCallback action); throws TransactionException {  
        TransactionStatus status = this.transactionManager.getTransaction(this);;  
        Object result = null;  
        try {  
            result = action.doInTransaction(status);;  
        }  
        catch (RuntimeException ex); {  
            // transactional code threw application exception -> rollback  
            rollbackOnException(status, ex);;  
            throw ex;  
        }  
        catch (Error err); {  
            // transactional code threw error -> rollback  
            rollbackOnException(status, err);;  
            throw err;  
        }  
        this.transactionManager.commit(status);;  
        return result;  
    }  

使用TransactionTempale如下

Object result = tt.execute(new TransactionCallback(){  
  public Object doTransaction(TransactionStatus status){  
  updateOperation();  
  return resultOfUpdateOperation();  
}  
}); 

使用TransactionCallback()可以返回一个值。如果使用TransactionCallbackWithoutResult则没有返回值。

二.直接使用PlatformTransactionManager

    Spring的事务处理中，通用的事务处理流程框架是由抽象事务管理器AbstractPlatformTransactionManager来提供的，而具体的底层事务处理实现，由PlatformTransactionManager的具体实现类来实现，如 DataSourceTransactionManager 、JtaTransactionManager和 HibernateTransactionManager等。

1.AbstractPlatformTransactionManager抽象事物处理器：

上一篇博客中，我们已经分析了抽象事物管理器AbstractPlatformTransactionManager的源码，了解它实现了PlatformTransactionManager平台事务管理器接口，提供了一系列设计好的事务模板方法，如事务提交、回滚等，这些模板方法的具体实现由具体的事务处理器来提供。

2.DataSourceTransactionManager事务处理器的实现：

针对JDBC连接提供的事务处理器实现，即数据源事务处理器把数据库Connection连接和当前线程进行绑定，通过直接调用数据库连接Connection的提交和回滚方法实现事务的提供和回滚处理。其部分源码如下：

public class DataSourceTransactionManager extends AbstractPlatformTransactionManager
		implements ResourceTransactionManager, InitializingBean {
	//注入数据源
	private DataSource dataSource;
//数据源事务处理器默认构造方法，创建一个数据源事务处理器实例，并设置允许嵌套事务
	public DataSourceTransactionManager() {
		setNestedTransactionAllowed(true);
	}
	//根据给定数据源，创建一个数据源事务处理器实例
	public DataSourceTransactionManager(DataSource dataSource) {
		this();
		setDataSource(dataSource);
		afterPropertiesSet();
	}
	//设置数据源
	public void setDataSource(DataSource dataSource) {
		if (dataSource instanceof TransactionAwareDataSourceProxy) {
			//如果数据源是一个事务包装数据源代理，则获取事务包装代理的目标数据源 
			this.dataSource = ((TransactionAwareDataSourceProxy) dataSource).getTargetDataSource();
		}
		else {
			this.dataSource = dataSource;
		}
	}
	//获取数据源
	public DataSource getDataSource() {
		return this.dataSource;
	}
	//数据源事务处理器对象构造方法的回调函数
	public void afterPropertiesSet() {
		if (getDataSource() == null) {
			throw new IllegalArgumentException("Property 'dataSource' is required");
		}
	}
public Object getResourceFactory() {
		return getDataSource();
	}
//创建事务，对数据库而言，是由Connection来完成事务工作的。该方法把数据库的//Connection对象放到一个ConnectionHolder对象中，然后封装到一个
//DataSourceTransactionObject对象中
	protected Object doGetTransaction() {
		//创建数据源事务对象
		DataSourceTransactionObject txObject = new DataSourceTransactionObject();
		//设置数据源事务对象对嵌套事务使用保存点
		txObject.setSavepointAllowed(isNestedTransactionAllowed());
		//从事务管理容器中获取存放数据库Connection的对象
		ConnectionHolder conHolder =
		    (ConnectionHolder) TransactionSynchronizationManager.getResource(this.dataSource);
		txObject.setConnectionHolder(conHolder, false);
		return txObject;
	}
	//判断是否已经存在事务
	protected boolean isExistingTransaction(Object transaction) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
	//根据存放数据库连接的ConnectionHolder的isTransactionActive属性来判断
		return (txObject.getConnectionHolder() != null && txObject.getConnectionHolder().isTransactionActive());
	}
	//处理事务开始的方法
	protected void doBegin(Object transaction, TransactionDefinition definition) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
		Connection con = null;
		try {
			//如果数据源事务对象的ConnectionHolder为null或者是事务同步的
			if (txObject.getConnectionHolder() == null ||
		txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
				//获取当前数据源的数据库连接
				Connection newCon = this.dataSource.getConnection();
				if (logger.isDebugEnabled()) {
					logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
				}
				//为数据源事务对象设置ConnectionHolder
				txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
			}
	//设置数据源事务对象的事务同步	txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
			//获取数据源事务对象的数据库连接
			con = txObject.getConnectionHolder().getConnection();
			//根据数据连接和事务属性，获取数据库连接的事务隔离级别
			Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
	//为数据源事务对象设置事务隔离级别
	txObject.setPreviousIsolationLevel(previousIsolationLevel);
			//如果数据库连接设置了自动事务提交属性，则关闭自动提交
			if (con.getAutoCommit()) {
				//保存数据库连接设置的自动连接到数据源事务对象中
				txObject.setMustRestoreAutoCommit(true);
				if (logger.isDebugEnabled()) {
					logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
				}
				//设置数据库连接自动事务提交属性为false，即禁止自动事务提交
				con.setAutoCommit(false);
			}
			//激活当前数据源事务对象的事务配置
			txObject.getConnectionHolder().setTransactionActive(true);
			//获取事务配置的超时时长
int timeout = determineTimeout(definition);
//如果事务配置的超时时长不等于事务的默认超时时长
			if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
		//数据源事务对象设置超时时长
		txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
			}
			//把当前数据库Connection和线程绑定
			if (txObject.isNewConnectionHolder()) {
		TransactionSynchronizationManager.bindResource(getDataSource(), txObject.getConnectionHolder());
			}
		}
		catch (Exception ex) {
			DataSourceUtils.releaseConnection(con, this.dataSource);
			throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
		}
	}
	//事务挂起
	protected Object doSuspend(Object transaction) {
		//获取事务对象
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
		//将事务对象中的ConnectionHolders设置为null
		txObject.setConnectionHolder(null);
		ConnectionHolder conHolder = (ConnectionHolder)
		//解除事务对象和当前线程的绑定	TransactionSynchronizationManager.unbindResource(this.dataSource);
		return conHolder;
	}
	//事务恢复
	protected void doResume(Object transaction, Object suspendedResources) {
		//获取已暂停事务的ConnectionHolder
		ConnectionHolder conHolder = (ConnectionHolder) suspendedResources;
		//重新将事务对象和当前线程绑定
		TransactionSynchronizationManager.bindResource(this.dataSource, conHolder);
	}
	//事务提交
	protected void doCommit(DefaultTransactionStatus status) {
		//获取事务对象
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
		//通过事务对象获取数据库连接
		Connection con = txObject.getConnectionHolder().getConnection();
		if (status.isDebug()) {
			logger.debug("Committing JDBC transaction on Connection [" + con + "]");
		}
		try {
			//使用数据库连接手动进行事务提交
			con.commit();
		}
		catch (SQLException ex) {
			throw new TransactionSystemException("Could not commit JDBC transaction", ex);
		}
	}
	//事务回滚
	protected void doRollback(DefaultTransactionStatus status) {
		//获取事务对象
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
		//通过事务对象获取数据库连接
		Connection con = txObject.getConnectionHolder().getConnection();
		if (status.isDebug()) {
			logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
		}
		try {
			//通过调用数据库连接的回滚方法完成事务回滚操作
			con.rollback();
		}
		catch (SQLException ex) {
			throw new TransactionSystemException("Could not roll back JDBC transaction", ex);
		}
	}
	//设置回滚
	protected void doSetRollbackOnly(DefaultTransactionStatus status) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Setting JDBC transaction [" + txObject.getConnectionHolder().getConnection() +
					"] rollback-only");
		}
		txObject.setRollbackOnly();
	}
	//操作完成之后清除操作
	protected void doCleanupAfterCompletion(Object transaction) {
		DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
		//移除当前线程绑定的ConnectionHolder
		if (txObject.isNewConnectionHolder()) {
	TransactionSynchronizationManager.unbindResource(this.dataSource);
		}
		Connection con = txObject.getConnectionHolder().getConnection();
		try {
		//如果事务对象保存了自动事务提交属性，则设置数据库连接的自动事务提交属性
			if (txObject.isMustRestoreAutoCommit()) {
				con.setAutoCommit(true);
			}
			//事务结束后重置数据库连接
			DataSourceUtils.resetConnectionAfterTransaction(con, txObject.getPreviousIsolationLevel());
		}
		catch (Throwable ex) {
			logger.debug("Could not reset JDBC Connection after transaction", ex);
		}
		//如果事务对象中有新的ConnectionHolder 
		if (txObject.isNewConnectionHolder()) {
			if (logger.isDebugEnabled()) {
				logger.debug("Releasing JDBC Connection [" + con + "] after transaction");
			}
			//释放数据库连接
			DataSourceUtils.releaseConnection(con, this.dataSource);
		}
		//清除事务对象的ConnectionHolder
		txObject.getConnectionHolder().clear();
	}
//数据源事务对象，内部类
	private static class DataSourceTransactionObject extends JdbcTransactionObjectSupport {
		//是否有新的ConnectionHolder
		private boolean newConnectionHolder;
		//是否保存自动提交
		private boolean mustRestoreAutoCommit;
		//设置ConnectionHolder
		public void setConnectionHolder(ConnectionHolder connectionHolder, boolean newConnectionHolder) {
			//为父类JdbcTransactionObjectSupport设置ConnectionHolder
			super.setConnectionHolder(connectionHolder);
			this.newConnectionHolder = newConnectionHolder;
		}
		public boolean isNewConnectionHolder() {
			return this.newConnectionHolder;
		}
		//调用父类JdbcTransactionObjectSupport的相关方法，查询收费存在事务
		public boolean hasTransaction() {
			return (getConnectionHolder() != null && getConnectionHolder().isTransactionActive());
		}
		//设置是否保存自动提交
		public void setMustRestoreAutoCommit(boolean mustRestoreAutoCommit) {
			this.mustRestoreAutoCommit = mustRestoreAutoCommit;
		}
		public boolean isMustRestoreAutoCommit() {
			return this.mustRestoreAutoCommit;
		}
		//设置数据库连接在操作失败是，是否只回滚处理
		public void setRollbackOnly() {
			getConnectionHolder().setRollbackOnly();
		}
		public boolean isRollbackOnly() {
			return getConnectionHolder().isRollbackOnly();
		}
	}
}

通过上述对数据源事务处理器的源码分析，我们看到，事务的提交、回滚等操作是通过直接调用数据库连接 Connection 的提交和回滚方法实现的，由于自动事务提交对应用程序性能影响很大，因此在进行事务提交时，我们首先禁止数据库连接的自动事务提交，事务提供操作通过手动实现。

3.HibernateTransactionManager事务处理器的实现：

相对于数据源的事务处理器来说，Hibernate的事务处理器相对要复杂一些，它是通过对Hibernate的会话Session的管理来完成事务处理实现的。Hibernate事务处理器的事务处理相关源码如下：

public class HibernateTransactionManager extends AbstractPlatformTransactionManager
		implements ResourceTransactionManager, BeanFactoryAware, InitializingBean {
	……
	//获取Hibernate事务
	protected Object doGetTransaction() {
		//创建Hibernate事务对象
		HibernateTransactionObject txObject = new HibernateTransactionObject();
		//根据是否允许嵌套事务设置事务对象是否允许保存点
		txObject.setSavepointAllowed(isNestedTransactionAllowed());
		//从线程中获取SessionHolder,SessionHolder是在事务开始时与线程绑定的。
		SessionHolder sessionHolder =
				(SessionHolder) TransactionSynchronizationManager.getResource(getSessionFactory());
		//如果获取到的SessionHolder不为null
		if (sessionHolder != null) {
			if (logger.isDebugEnabled()) {
				logger.debug("Found thread-bound Session [" +
				SessionFactoryUtils.toString(sessionHolder.getSession()) + "] for Hibernate transaction");
			}
			//把获取到的SessionHolder设置到Hibernate事务对象中
			txObject.setSessionHolder(sessionHolder);
		}
		//如果当前Hibernate事务处理器有被管理的Hibernate Session
		else if (this.hibernateManagedSession) {
			try {
				//获取当前的Hibernate Session
				Session session = getSessionFactory().getCurrentSession();
				if (logger.isDebugEnabled()) {
					logger.debug("Found Hibernate-managed Session [" +
							SessionFactoryUtils.toString(session) + "] for Spring-managed transaction");
				}
				//设置Hibernate事务对象已经存在指定的Session
				txObject.setExistingSession(session);
			}
			catch (HibernateException ex) {
				throw new DataAccessResourceFailureException(
						"Could not obtain Hibernate-managed Session for Spring-managed transaction", ex);
			}
		}
		//如果获取到的数据源不为null
		if (getDataSource() != null) {
			//将获取到的数据源和当前线程绑定
			ConnectionHolder conHolder = (ConnectionHolder)
	TransactionSynchronizationManager.getResource(getDataSource());
			txObject.setConnectionHolder(conHolder);
		}
		return txObject;
	}
	//是否已存在事务
	protected boolean isExistingTransaction(Object transaction) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) transaction;
//根据事务对象是否存在Spring管理的事务，或者通过判断是否存在Hibernate //Session或者事务对象中有被Hibernate管理的事务
		return (txObject.hasSpringManagedTransaction() ||
				(this.hibernateManagedSession && txObject.hasHibernateManagedTransaction()));
	}
	//处理事务开始
	protected void doBegin(Object transaction, TransactionDefinition definition) {
		//获取事务对象
		HibernateTransactionObject txObject = (HibernateTransactionObject) transaction;
		//如果事务对象有ConnectionHolder，且事务对象的数据库连接不是事务同步的
		if (txObject.hasConnectionHolder() && !txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
			throw new IllegalTransactionStateException(
					"Pre-bound JDBC Connection found! HibernateTransactionManager does not support " +
					"running within DataSourceTransactionManager if told to manage the DataSource itself. " +
					"It is recommended to use a single HibernateTransactionManager for all transactions " +
					"on a single DataSource, no matter whether Hibernate or JDBC access.");
		}
		Session session = null;
		try {
			//如果事务对象的SessionHolder为null，或者事务对象Hibernate
			//Session是事务同步的
			if (txObject.getSessionHolder() == null || txObject.getSessionHolder().isSynchronizedWithTransaction()) {
				//获取Hibernate事务处理器中的实体拦截器
				Interceptor entityInterceptor = getEntityInterceptor();
				//获取Hibernate Session，如果实体拦截器不为null，则打开指定
//实体拦截器的Session，如果实体拦截器为null，则打开新Session
				Session newSession = (entityInterceptor != null ?
					getSessionFactory().openSession(entityInterceptor) : getSessionFactory().openSession());
				if (logger.isDebugEnabled()) {
					logger.debug("Opened new Session [" + SessionFactoryUtils.toString(newSession) +
							"] for Hibernate transaction");
				}
				//将获取的Hibernate Session设置到事务对象中
				txObject.setSession(newSession);
			}
//如果Hibernate事务处理器中的SessionHolder不为null，则
//获取SessionHolder中已有的Hibernate Session
			session = txObject.getSessionHolder().getSession();
			//允许为JDBC连接改变事务设置
			if (this.prepareConnection && isSameConnectionForEntireSession(session)) {
				if (logger.isDebugEnabled()) {
					logger.debug(
							"Preparing JDBC Connection of Hibernate Session [" + SessionFactoryUtils.toString(session) + "]");
				}
				//获取Session连接
				Connection con = session.connection();
				//获取事务的隔离级别
				Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
			//设置事务对象的事务隔离级别	txObject.setPreviousIsolationLevel(previousIsolationLevel);
			}
			//不允许为JDBC连接改成事务设置
			else {
				//如果事务隔离级别不是默认事务隔离级别
				if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT) {
					throw new InvalidIsolationLevelException(
							"HibernateTransactionManager is not allowed to support custom isolation levels: " +
							"make sure that its 'prepareConnection' flag is on (the default) and that the " +
							"Hibernate connection release mode is set to 'on_close' (SpringTransactionFactory's default). " +
							"Make sure that your LocalSessionFactoryBean actually uses SpringTransactionFactory: Your " +
							"Hibernate properties should *not* include a 'hibernate.transaction.factory_class' property!");
				}
				if (logger.isDebugEnabled()) {
					logger.debug(
							"Not preparing JDBC Connection of Hibernate Session [" + SessionFactoryUtils.toString(session) + "]");
				}
			}
			//如果事务是只读，且事务对象是新的Hibernate Session
			if (definition.isReadOnly() && txObject.isNewSession()) {
				//设置Hibernate Session刷新模式为手动
				session.setFlushMode(FlushMode.MANUAL);
			}
			//如果事务是非只读的，且事务对象不是新Hibernate Session
			if (!definition.isReadOnly() && !txObject.isNewSession()) {
				//或者Hibernate的刷新模式
				FlushMode flushMode = session.getFlushMode();
				//设置Session的刷新模式
				if (flushMode.lessThan(FlushMode.COMMIT)) {
					session.setFlushMode(FlushMode.AUTO);
				//为事务对象设置刷新模式	txObject.getSessionHolder().setPreviousFlushMode(flushMode);
				}
			}
			Transaction hibTx;
			//获取事务超时时长
			int timeout = determineTimeout(definition);
			//如果事务配置的超时时长不是事务默认超时时长
			if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
				//获取Hibernate Session事务
				hibTx = session.getTransaction();
				//为事务对象设置超时时长
				hibTx.setTimeout(timeout);
				//开启事务
				hibTx.begin();
			}
			//如果事务配置的超时时长是默认超时时长
			else {
				//通过Hibernate Session直接开启事务
				hibTx = session.beginTransaction();
			}
			//把事务设置到事务对象的SessionHolder中，并且线程绑定
			txObject.getSessionHolder().setTransaction(hibTx);
			//如果数据源不为null，即设置了数据源
			if (getDataSource() != null) {
				//使用Hibernate Session打开数据库连接
				Connection con = session.connection();
				//创建ConnectionHolder
				ConnectionHolder conHolder = new ConnectionHolder(con);
				//设置超时时长
				if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
					conHolder.setTimeoutInSeconds(timeout);
				}
				if (logger.isDebugEnabled()) {
					logger.debug("Exposing Hibernate transaction as JDBC transaction [" + con + "]");
				}
			//将数据源和JDBC ConnectionHolder绑定到当前线程	TransactionSynchronizationManager.bindResource(getDataSource(), conHolder);
				//将创建的JDBC ConnectionHolder设置到事务对象中
				txObject.setConnectionHolder(conHolder);
			}
			//如果事务对象中的SessionHolder是新的
			if (txObject.isNewSessionHolder()) {
			//当SessionHolder和当前线程绑定起来	TransactionSynchronizationManager.bindResource(getSessionFactory(), txObject.getSessionHolder());
			}
		//设置事务对象中的SessionHolder是事务同步的	txObject.getSessionHolder().setSynchronizedWithTransaction(true);
		}
		//事务开启过程中异常处理
		catch (Exception ex) {
			if (txObject.isNewSession()) {
				try {
					//如果Session的事务上激活的，回滚Session的事务
					if (session.getTransaction().isActive()) {
						session.getTransaction().rollback();
					}
				}
				catch (Throwable ex2) {
					logger.debug("Could not rollback Session after failed transaction begin", ex);
				}
				finally {
					//关闭Session
					SessionFactoryUtils.closeSession(session);
				}
			}
			throw new CannotCreateTransactionException("Could not open Hibernate Session for transaction", ex);
		}
	}
	//事务挂起
	protected Object doSuspend(Object transaction) {
		HibernateTransactionObject txObject = (HibernateTransactionObject) transaction;
		//把当前的SessionHolder从线程中和事务对象中释放
		txObject.setSessionHolder(null);
		//解析SessionHolder和线程的绑定
		SessionHolder sessionHolder =
				(SessionHolder) TransactionSynchronizationManager.unbindResource(getSessionFactory());
		txObject.setConnectionHolder(null);
		ConnectionHolder connectionHolder = null;
		//解除数据源和线程的绑定
		if (getDataSource() != null) {
			connectionHolder = (ConnectionHolder) TransactionSynchronizationManager.unbindResource(getDataSource());
		}
		return new SuspendedResourcesHolder(sessionHolder, connectionHolder);
	}
	//事务恢复
	protected void doResume(Object transaction, Object suspendedResources) {
		SuspendedResourcesHolder resourcesHolder = (SuspendedResourcesHolder) suspendedResources;
		//如果事务管理器中有SessionFactory
		if (TransactionSynchronizationManager.hasResource(getSessionFactory())) {
	//解除SessionFactory和当前线程的绑定
	TransactionSynchronizationManager.unbindResource(getSessionFactory());
		}
	//如果事务管理器中没有SessionFactory，则将Session和当前线程绑定	TransactionSynchronizationManager.bindResource(getSessionFactory(), resourcesHolder.getSessionHolder());
		if (getDataSource() != null) {
		TransactionSynchronizationManager.bindResource(getDataSource(), resourcesHolder.getConnectionHolder());
		}
	}
	//准备提交
	protected void prepareForCommit(DefaultTransactionStatus status) {
		//如果事务配置为FlushBeforeCommit，并且是新事务
		if (this.earlyFlushBeforeCommit && status.isNewTransaction()) {
			//获取事务对象
			HibernateTransactionObject txObject = (HibernateTransactionObject) status.getTransaction();
			//回去事务对象中的Session
			Session session = txObject.getSessionHolder().getSession();
			//如果Session的刷新模式不低于COMMIT
			if (!session.getFlushMode().lessThan(FlushMode.COMMIT)) {
				logger.debug("Performing an early flush for Hibernate transaction");
				try {
					//刷新Session
					session.flush();
				}
				catch (HibernateException ex) {
					throw convertHibernateAccessException(ex);
				}
				finally {
					//把Session的刷新模式设置为MANUAL
					session.setFlushMode(FlushMode.MANUAL);
				}
			}
		}
	}
	//提交处理
	protected void doCommit(DefaultTransactionStatus status) {
		//获取当前的Hibernate事务对象
		HibernateTransactionObject txObject = (HibernateTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Committing Hibernate transaction on Session [" +SessionFactoryUtils.toString(txObject.getSessionHolder().getSession()) + "]");
		}
		try {
			//通过Hibernate事务完成提交
			txObject.getSessionHolder().getTransaction().commit();
		}
		catch (org.hibernate.TransactionException ex) {
			throw new TransactionSystemException("Could not commit Hibernate transaction", ex);
		}
		catch (HibernateException ex) {
			throw convertHibernateAccessException(ex);
		}
	}
	//回滚处理
	protected void doRollback(DefaultTransactionStatus status) {
		//获取Hibernate事务对象
		HibernateTransactionObject txObject = (HibernateTransactionObject) status.getTransaction();
		if (status.isDebug()) {
			logger.debug("Rolling back Hibernate transaction on Session ["+SessionFactoryUtils.toString(txObject.getSessionHolder().getSession()) + "]");
		}
		try {
			//通过Hibernate事务执行回滚操作
			txObject.getSessionHolder().getTransaction().rollback();
		}
		catch (org.hibernate.TransactionException ex) {
			throw new TransactionSystemException("Could not roll back Hibernate transaction", ex);
		}
		catch (HibernateException ex) {
			throw convertHibernateAccessException(ex);
		}
		finally {
			if (!txObject.isNewSession() && !this.hibernateManagedSession) {
				//清除事务对象中的Hibernate Session
				txObject.getSessionHolder().getSession().clear();
			}
		}
	}
……
	}

通过上面对 Hibernate 事务处理器的分析，我们看到真正执行提交、回滚等事务操作的还是 Hibernate Transaction 事务对象，这与单独直接使用 Hibernate 没有什么区别，只是 Spring 将其做了通用封装，更加方便使用。