@Transactional嵌套事务失效异常Transaction rolled back because it has been marked as rollback-only
摘要：注解@Transactional嵌套事务失效，抛出异常ransaction rolled back because it has been marked as rollback-only，解决办法内部事务开启新事务。
问题描述
有段事务嵌套的代码，每次执行完都会报“Transaction rolled back because it has been marked as rollback-only”异常：
2022-04-02 07:01:47.810 [http-nio-7032-exec-1] INFO -c.c.i.impl.BarServiceImpl - 调用抛异常的方法
2022-04-02 07:01:47.819 [http-nio-7032-exec-1] INFO -c.c.i.impl.FarServiceImpl - 我抛出 runtime exception
2022-04-02 07:01:47.819 [http-nio-7032-exec-1] ERROR-c.c.i.impl.BarServiceImpl - 抛异常了，emo，
2022-04-02 07:01:47.819 [http-nio-7032-exec-1] INFO -c.c.i.impl.BarServiceImpl - 事务正常回滚？
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)
更多事务失效的场景，请戳《注解@Transactional事务失效的常见场景》。
问题分析
错误代码如下：
@Slf4j
@Service
public class BarServiceImpl implements BarService {
@Autowired
private FarService farService;
@Override
@Transactional
public void bar() {
log.info("调用抛异常的方法");
try {
farService.far();
} catch (Exception e) {
log.error("抛异常了，emo，", e.getMessage());
}
log.info("事务正常回滚？");
}
}
FarService中far函数的实现如下：
@Slf4j
@Service
public class FarServiceImpl implements FarService {
@Override
@Transactional
public void far() {
log.info("我抛出 runtime exception");
throw new NullPointerException("空指针了");
}
}
实现逻辑分析
1.两个添加 @Transactional的方法有调用关系，在接口BarService调用了接口FarService；
2.far()报异常了，但没有进行try catch捕获；
3.在bar() 中进行了try catch捕获。
在这种情况下，外层事务（BarService）和内层事务（FarService）共用同一个事务，任何一个出现异常，都会在bar()执行完毕后回滚。因为far()报异常，会把当前事务标志成rollback-only，所以，bar()的事务也需要回滚。由于bar()方法捕捉异常后一直往下走，等方法结束commit的时候会报错，提示：
org.springframework.transaction.UnexpectedRollbackException: Transaction rolled back because it has been marked as rollback-only
解决办法
小编Wiener在此提供三种解决策略：
1.被调用方法自己对异常做try catch处理。
2.修改事务传播行为。如果希望内层事务回滚，但不影响外层事务提交，需要将内层事务新开一个事务，例如@Transactional的事务传播行为修改为 @Transactional(propagation = Propagation.REQUIRES_NEW) 。
3.在外层事务不对内层事务的方法far()进行异常捕获，这样会自动抛出内层事务的错误，而不是报UnexpectedRollbackException。
源码分析
如果内部事务状态是PROPAGATION_SUPPORTS 或 PROPAGATION_REQUIRED或PROPAGATION_MANDATORY，将会在外层事务中运行，回滚的时候，并不执行回滚，只是标记一下回滚状态，当外层事务提交的时候，会先判断ConnectionHolder中的回滚状态，如果已经标记为回滚，则不会提交，而是外层事务进行回滚
查看异常信息，我们知道UnexpectedRollbackException是从类AbstractPlatformTransactionManager.java 的 line 870 抛出的，源码如下：
/**
* 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);
}
}
由此可见，内部事务因为抛异常，已经把事务标记为rollback-only。而unexpectedRollback为true，则是由调用方传入的，查看调用方AbstractPlatformTransactionManager.commit代码可知，直接传入了 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;
// 如果在事务链中已经被标记回滚，那么不会尝试提交事务，直接回滚
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");
}
// 进行事务回滚，并且抛出一个异常
processRollback(defStatus, true);
return;
}
// 没有被标记为回滚，这里才真正判断是否提交
processCommit(defStatus);
}
结束语
工作中处处都需要学习，有时候看似简单的一个异常问题排查，可以让你深入学习后收获各种知识。所以在学习中请不求甚解，用阅读源码的实际行动，打破坐吃山空的思维，不仅要了解这个知识点，也要熟悉为什么要这么做。如此以来，遇到异常问题的时候才可以避免像铁拳打到棉花，无所着力。
Buy me a coffee. ☕Get red packets.
