接第2节内容，这是第6点具体解析

事务提交逻辑如下：

  1. 判断事务是否曾经实现，如果实现抛出异样
  2. 判断事务是否曾经被标记成回滚，则执行回滚操作
  3. 嵌入事务标记回滚，如果嵌入事务抛出了异样执行了回滚，然而在调用方把嵌入事务的异样个捕捉没有抛出，就会执行这一步。
  4. 提交事务

代码如下：

@Overridepublic final void commit(TransactionStatus status) throws TransactionException {    //1. 判断事务是不是曾经实现    if (status.isCompleted()) {        throw new IllegalTransactionStateException(                "Transaction is already completed - do not call commit or rollback more than once per transaction");    }    DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status;    //2. 如果在事务链中曾经被标记回滚，那么不会尝试提交事务，间接回滚，不过我没找到在哪设置这个值    if (defStatus.isLocalRollbackOnly()) {        if (defStatus.isDebug()) {            logger.debug("Transactional code has requested rollback");        }        processRollback(defStatus);        return;    }    //3. shouldCommitOnGlobalRollbackOnly()默认返回false，isGlobalRollbackOnly是在嵌入事务回滚的时候赋值的    if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {        if (defStatus.isDebug()) {            logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");        }        processRollback(defStatus);        // Throw UnexpectedRollbackException only at outermost transaction boundary        // or if explicitly asked to.        if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) {            throw new UnexpectedRollbackException(                    "Transaction rolled back because it has been marked as rollback-only");        }        return;    }    //4. 提交事务    processCommit(defStatus);}