Spring框架学习[Spring具体事务处理器的实现](五)
} }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