@Override
public boolean rollbackOn(Throwable ex) {
 if (logger.isTraceEnabled()) {
  logger.trace("Applying rules to determine whether transaction should rollback on " + ex);
 }

 RollbackRuleAttribute winner = null;
 int deepest = Integer.MAX_VALUE;

 //rollbackRules保存@Transactional注解中rollbackFor、rollbackForClassName、noRollbackForClassName配置的值
 if (this.rollbackRules != null) {
  for (RollbackRuleAttribute rule : this.rollbackRules) {
   int depth = rule.getDepth(ex);
   if (depth >= 0 && depth < deepest) {
    deepest = depth;
    winner = rule;
   }
  }
 }

 if (logger.isTraceEnabled()) {
  logger.trace("Winning rollback rule is: " + winner);
 }

 // User superclass behavior (rollback on unchecked) if no rule matches.
 //若@Transactional沒有配置，默認(rèn)調(diào)用父類的
 if (winner == null) {
  logger.trace("No relevant rollback rule found: applying default rules");
  return super.rollbackOn(ex);
 }

 return !(winner instanceof NoRollbackRuleAttribute);
}

//super
@Override
public boolean rollbackOn(Throwable ex) {
 return (ex instanceof RuntimeException || ex instanceof Error);
}

private void processRollback(DefaultTransactionStatus status) {
 try {
  try {
   triggerBeforeCompletion(status);
   //如果有安全點(diǎn)，回滾至安全點(diǎn)
   if (status.hasSavepoint()) {
    if (status.isDebug()) {
     logger.debug("Rolling back transaction to savepoint");
    }
    status.rollbackToHeldSavepoint();
   }
   //如果是新事務(wù)，回滾事務(wù)
   else if (status.isNewTransaction()) {
    if (status.isDebug()) {
     logger.debug("Initiating transaction rollback");
    }
    doRollback(status);
   }
   //如果有事務(wù)但不是新事務(wù)，則把標(biāo)記事務(wù)狀態(tài)，等事務(wù)鏈執(zhí)行完畢后統(tǒng)一回滾
   else if (status.hasTransaction()) {
    if (status.isLocalRollbackOnly() || isGlobalRollbackOnParticipationFailure()) {
     if (status.isDebug()) {
      logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
     }
     doSetRollbackOnly(status);
    }
    else {
     if (status.isDebug()) {
      logger.debug("Participating transaction failed - letting transaction originator decide on rollback");
     }
    }
   }
   else {
    logger.debug("Should roll back transaction but cannot - no transaction available");
   }
  }
  catch (RuntimeException ex) {
   triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
   throw ex;
  }
  catch (Error err) {
   triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
   throw err;
  }
  triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
 }
 finally {
  //清空記錄的資源并將掛起的資源恢復(fù)
  cleanupAfterCompletion(status);
 }
}

@Override
public final void commit(TransactionStatus status) throws TransactionException {
 //1. 判斷事務(wù)是不是已經(jīng)完成
 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. 如果在事務(wù)鏈中已經(jīng)被標(biāo)記回滾，那么不會(huì)嘗試提交事務(wù)，直接回滾，不過我沒找到在哪設(shè)置這個(gè)值
 if (defStatus.isLocalRollbackOnly()) {
  if (defStatus.isDebug()) {
   logger.debug("Transactional code has requested rollback");
  }
  processRollback(defStatus);
  return;
 }
 //3. shouldCommitOnGlobalRollbackOnly()默認(rèn)返回false，isGlobalRollbackOnly是在嵌入事務(wù)回滾的時(shí)候賦值的
 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. 提交事務(wù)
 processCommit(defStatus);
}