@Transactional巢狀事務失效異常Transaction rolled back because it has been marked as rollback-only
摘要：註解@Transactional巢狀事務失效，丟擲異常ransaction rolled back because it has been marked as rollback-only，解決辦法內部事務開啟新事務。
問題描述
有段事務巢狀的程式碼，每次執行完都會報“Transaction rolled back because it has been marked as rollback-only”異常：
2022-04-02 07:01:47.810 [http-nio-7032-exec-1] INFO -c.c.i.impl.BarServiceImpl - 呼叫拋異常的方法 2022-04-02 07:01:47.819 [http-nio-7032-exec-1] INFO -c.c.i.impl.FarServiceImpl - 我丟擲 runtime exception 2022-04-02 07:01:47.819 [http-nio-7032-exec-1] ERROR-c.c.i.impl.BarServiceImpl - 拋異常了，emo， 2022-04-02 07:01:47.819 [http-nio-7032-exec-1] INFO -c.c.i.impl.BarServiceImpl - 事務正常回滾？ 2022-04-02 07:01:47.825 [http-nio-7032-exec-1] ERROR-c.c.i.m.a.w.ControllerExceptionAdvice - error org.springframework.transaction.UnexpectedRollbackException: Transaction rolled back because it has been marked as rollback-only at org.springframework.transaction.support.AbstractPlatformTransactionManager.processRollback(AbstractPlatformTransactionManager.java:870) at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:707) at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:654) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:407) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750) at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:692)
更多事務失效的場景，請戳《註解@Transactional事務失效的常見場景》。
問題分析
錯誤程式碼如下：
@Slf4j @Service public class BarServiceImpl implements BarService { @Autowired private FarService farService; @Override @Transactional public void bar() { log.info("呼叫拋異常的方法"); try { farService.far(); } catch (Exception e) { log.error("拋異常了，emo，", e.getMessage()); } log.info("事務正常回滾？"); } }
FarService中far函式的實現如下：
@Slf4j
@Service
public class FarServiceImpl implements FarService {
@Override
@Transactional
public void far() {
log.info("我丟擲 runtime exception");
throw new NullPointerException("空指標了");
}
}
實現邏輯分析
1.兩個新增 @Transactional的方法有呼叫關係，在介面BarService呼叫了介面FarService；
2.far()報異常了，但沒有進行try catch捕獲；
3.在bar() 中進行了try catch捕獲。
在這種情況下，外層事務（BarService）和內層事務（FarService）共用同一個事務，任何一個出現異常，都會在bar()執行完畢後回滾。因為far()報異常，會把當前事務標誌成rollback-only，所以，bar()的事務也需要回滾。由於bar()方法捕捉異常後一直往下走，等方法結束commit的時候會報錯，提示：
org.springframework.transaction.UnexpectedRollbackException: Transaction rolled back because it has been marked as rollback-only
解決辦法
小編Wiener在此提供三種解決策略：
1.被呼叫方法自己對異常做try catch處理。
2.修改事務傳播行為。如果希望內層事務回滾，但不影響外層事務提交，需要將內層事務新開一個事務，例如@Transactional的事務傳播行為修改為 @Transactional(propagation = Propagation.REQUIRES_NEW) 。
3.在外層事務不對內層事務的方法far()進行異常捕獲，這樣會自動丟擲內層事務的錯誤，而不是報UnexpectedRollbackException。
原始碼分析
如果內部事務狀態是PROPAGATION_SUPPORTS 或 PROPAGATION_REQUIRED或PROPAGATION_MANDATORY，將會在外層事務中執行，回滾的時候，並不執行回滾，只是標記一下回滾狀態，當外層事務提交的時候，會先判斷ConnectionHolder中的回滾狀態，如果已經標記為回滾，則不會提交，而是外層事務進行回滾
檢視異常資訊，我們知道UnexpectedRollbackException是從類AbstractPlatformTransactionManager.java 的 line 870 丟擲的，原始碼如下：
/**
* Process an actual rollback.
* The completed flag has already been checked.
* @param status object representing the transaction
* @throws TransactionException in case of rollback failure
*/
private void processRollback(DefaultTransactionStatus status, boolean unexpected) {
try {
boolean unexpectedRollback = unexpected;
try {
triggerBeforeCompletion(status);
if (status.hasSavepoint()) {
if (status.isDebug()) {
logger.debug("Rolling back transaction to savepoint");
}
status.rollbackToHeldSavepoint();
}
else if (status.isNewTransaction()) {
if (status.isDebug()) {
logger.debug("Initiating transaction rollback");
}
doRollback(status);
}
else {
// Participating in larger transaction
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");
}
// Unexpected rollback only matters here if we're asked to fail early
if (!isFailEarlyOnGlobalRollbackOnly()) {
unexpectedRollback = false;
}
}
}
catch (RuntimeException | Error ex) {
triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
throw ex;
}
triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
// Raise UnexpectedRollbackException if we had a global rollback-only marker
if (unexpectedRollback) {
throw new UnexpectedRollbackException(
"Transaction rolled back because it has been marked as rollback-only");
}
}
finally {
cleanupAfterCompletion(status);
}
}
由此可見，內部事務因為拋異常，已經把事務標記為rollback-only。而unexpectedRollback為true，則是由呼叫方傳入的，檢視呼叫方AbstractPlatformTransactionManager.commit程式碼可知，直接傳入了 processRollback(defStatus, true)：
@Override
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;
// 如果在事務鏈中已經被標記回滾，那麼不會嘗試提交事務，直接回滾
if (defStatus.isLocalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Transactional code has requested rollback");
}
processRollback(defStatus, false);
return;
}
if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
}
// 進行事務回滾，並且丟擲一個異常
processRollback(defStatus, true);
return;
}
// 沒有被標記為回滾，這裡才真正判斷是否提交
processCommit(defStatus);
}
結束語
工作中處處都需要學習，有時候看似簡單的一個異常問題排查，可以讓你深入學習後收穫各種知識。所以在學習中請不求甚解，用閱讀原始碼的實際行動，打破坐吃山空的思維，不僅要了解這個知識點，也要熟悉為什麼要這麼做。如此以來，遇到異常問題的時候才可以避免像鐵拳打到棉花，無所著力。