Spring事务源码解析之事务提交篇

阅读须知

• Spring源码版本：4.3.8
• 文章中使用/* */注释的方法会做深入分析

正文

承接上文，我们来看事务的提交操作：
TransactionAspectSupport：

protected void commitTransactionAfterReturning(TransactionInfo txInfo) {
    if (txInfo != null && txInfo.hasTransaction()) {
        if (logger.isTraceEnabled()) {
            logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() + "]");
        }
        /* 事务提交 */
        txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
    }
}

AbstractPlatformTransactionManager：

public final void commit(TransactionStatus status) throws TransactionException {
    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;
    if (defStatus.isLocalRollbackOnly()) {
        if (defStatus.isDebug()) {
            logger.debug("Transactional code has requested rollback");
        }
        processRollback(defStatus); // 回滚操作
        return;
    }
    if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
        if (defStatus.isDebug()) {
            logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
        }
        processRollback(defStatus); // 回滚操作
        if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) {
            throw new UnexpectedRollbackException(
                "Transaction rolled back because it has been marked as rollback-only");
        }
        return;
    }
    processCommit(defStatus); /* 提交操作 */
}

在Spring事务回滚源码分析的文章中我们提到了如果当前事务不是独立的事务，也没有保存点，在回滚的时候只是设置一个回滚标记，由外部事务提交时统一进行整体事务的回滚，这个回滚操作就是在这里进行。
AbstractPlatformTransactionManager：

private void processCommit(DefaultTransactionStatus status) throws TransactionException {
    try {
        boolean beforeCompletionInvoked = false;
        try {
            prepareForCommit(status);
            triggerBeforeCommit(status);
            triggerBeforeCompletion(status);
            beforeCompletionInvoked = true;
            boolean globalRollbackOnly = false;
            if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) {
                globalRollbackOnly = status.isGlobalRollbackOnly();
            }
            if (status.hasSavepoint()) {
                if (status.isDebug()) {
                    logger.debug("Releasing transaction savepoint");
                }
                status.releaseHeldSavepoint(); // 释放保存点信息
            }
            else if (status.isNewTransaction()) {
                if (status.isDebug()) {
                    logger.debug("Initiating transaction commit");
                }
                doCommit(status); /* 独立事务则提交 */
            }
            if (globalRollbackOnly) {
                throw new UnexpectedRollbackException(
                    "Transaction silently rolled back because it has been marked as rollback-only");
            }
        }
        catch (UnexpectedRollbackException ex) {
            triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
            throw ex;
        }
        catch (TransactionException ex) {
            if (isRollbackOnCommitFailure()) {
                doRollbackOnCommitException(status, ex);
            }
            else {
                triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
            }
            throw ex;
        }
        catch (RuntimeException ex) {
            if (!beforeCompletionInvoked) {
                triggerBeforeCompletion(status);
            }
            doRollbackOnCommitException(status, ex); // 提交异常则回滚
            throw ex;
        }
        catch (Error err) {
            if (!beforeCompletionInvoked) {
                triggerBeforeCompletion(status);
            }
            doRollbackOnCommitException(status, err);
            throw err;
        }
        try {
            triggerAfterCommit(status);
        }
        finally {
            triggerAfterCompletion(status, TransactionSynchronization.STATUS_COMMITTED);
        }

    }
    finally {
        cleanupAfterCompletion(status); // 清理事务信息
    }
}

其中回滚和事务清理流程我们在Spring事务回滚源码分析的文章中已经进行过详细说明，不再赘述。
DataSourceTransactionManager：

protected void doCommit(DefaultTransactionStatus status) {
    DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
    Connection con = txObject.getConnectionHolder().getConnection();
    if (status.isDebug()) {
        logger.debug("Committing JDBC transaction on Connection [" + con + "]");
    }
    try {
        con.commit();
    }
    catch (SQLException ex) {
        throw new TransactionSystemException("Could not commit JDBC transaction", ex);
    }
}

提交操作也是很简单的调用数据库连接底层API的commit方法。到这里，整个Spring事务的源码分析就完成了。