之前经常报"Transaction rolled back because it has been marked as rollback-only"这个异常

字面意思是"事务回滚了，因为它被标记了必须回滚"，最开始完全不懂事务的嵌套，每次出现这个错误都想知道为什么，但是总是不能重现，后面反复折腾终于弄明白了怎么回事。

之前不能重现的一个重要原因是：同一个类，内部方法调用不走代理，spring基于注解的事务是基于代理的，不走代理，被调用的方法就不受事务管理代码的控制，自然无法重现问题.

测试代码:

TestController

    @Autowired
    TestRollbackService testRollbackService;

    @RequestMapping("/test1")
    public void test1(){
        try{
            testRollbackService.test1();
        }catch(Exception e){
            e.printStackTrace();
        }
    }

TestRollbackServiceImpl

    @Autowired
    StudentMapper studentMapper;

    @Autowired
    TestTransactionService testTransactionService;

    @Transactional(rollbackFor = Exception.class)
    public void test1(){
        Student studentSelect = new Student();
        studentSelect.setId(new Long(1));
        Student student = studentMapper.selectByPrimaryKey(studentSelect);
        try{
            testTransactionService.test2();
        }catch(Exception e){
            e.printStackTrace();
        }
    }

TestTransactionServiceImpl

@Autowired
StudentMapper studentMapper;

@Transactional(rollbackFor = Exception.class)
public void test2(){
    Student studentForInsert = new Student();
    studentForInsert.setId(new Long(19));
    studentForInsert.setName("测试11");
    studentForInsert.setScore(new BigDecimal(69));
    studentMapper.updateByPrimaryKey(studentForInsert);
    System.out.println(1/0);
}

TestRollbackService.test1(方法A)中调用了TestTransactionService.test2(方法B)，上述代码可以触发回滚异常的报错

两个方法都加了事务注解，并且两个方法都会受到到事务管理的拦截器增强，并且事务传播的方式都是默认的，也就是REQUIRED，当已经存在事务的时候就加入事务，没有就创建事务。这里A和B都受事务控制，并且是处于同一个事务的。

A调用B，A中抓了B的异常，当B发生异常的时候，B的操作应该回滚，但是A吃了异常，A方法中没有产生异常，所以A的操作又应该提交，二者是相互矛盾的。

spring的事务关联拦截器在抓到B的异常后就会标记rollback-only为true，当A执行完准备提交后，发现rollback-only为true，也会回滚，并抛出异常告诉调用者。

程序时序图如下:

 

1.程序入口

程序入口肯定是代理类，这里走是cglib的代理

入口方法:

org.springframework.aop.framework.CglibAopProxy.DynamicAdvisedInterceptor#intercept

该方法中

retVal = (new CglibAopProxy.CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy)).proceed();

继续调用

org.springframework.aop.framework.ReflectiveMethodInvocation#proceed

然后到了事务管理的拦截器

org.springframework.transaction.interceptor.TransactionInterceptor#invoke

@Nullable
public Object invoke(MethodInvocation invocation) throws Throwable {
    Class<?> targetClass = invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null;
    Method var10001 = invocation.getMethod();
    invocation.getClass();
    return this.invokeWithinTransaction(var10001, targetClass, invocation::proceed);
}

2.invokeWithinTransaction(事务管理的主方法)

 @Nullable
    protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targetClass, TransactionAspectSupport.InvocationCallback invocation) throws Throwable {
        TransactionAttributeSource tas = this.getTransactionAttributeSource();
        TransactionAttribute txAttr = tas != null ? tas.getTransactionAttribute(method, targetClass) : null;
        PlatformTransactionManager tm = this.determineTransactionManager(txAttr);
        String joinpointIdentification = this.methodIdentification(method, targetClass, txAttr);
        Object result;
        if (txAttr != null && tm instanceof CallbackPreferringPlatformTransactionManager) {
            TransactionAspectSupport.ThrowableHolder throwableHolder = new TransactionAspectSupport.ThrowableHolder();

            try {
                result = ((CallbackPreferringPlatformTransactionManager)tm).execute(txAttr, (status) -> {
                    TransactionAspectSupport.TransactionInfo txInfo = this.prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);

                    Object var9;
                    try {
                        Object var8 = invocation.proceedWithInvocation();
                        return var8;
                    } catch (Throwable var13) {
                        if (txAttr.rollbackOn(var13)) {
                            if (var13 instanceof RuntimeException) {
                                throw (RuntimeException)var13;
                            }

                            throw new TransactionAspectSupport.ThrowableHolderException(var13);
                        }

                        throwableHolder.throwable = var13;
                        var9 = null;
                    } finally {
                        this.cleanupTransactionInfo(txInfo);
                    }

                    return var9;
                });
                if (throwableHolder.throwable != null) {
                    throw throwableHolder.throwable;
                } else {
                    return result;
                }
            } catch (TransactionAspectSupport.ThrowableHolderException var19) {
                throw var19.getCause();
            } catch (TransactionSystemException var20) {
                if (throwableHolder.throwable != null) {
                    this.logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
                    var20.initApplicationException(throwableHolder.throwable);
                }

                throw var20;
            } catch (Throwable var21) {
                if (throwableHolder.throwable != null) {
                    this.logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
                }

                throw var21;
            }
        } else {
            TransactionAspectSupport.TransactionInfo txInfo = this.createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
            result = null;

            try {
                result = invocation.proceedWithInvocation();
            } catch (Throwable var17) {
                this.completeTransactionAfterThrowing(txInfo, var17);
                throw var17;
            } finally {
                this.cleanupTransactionInfo(txInfo);
            }

            this.commitTransactionAfterReturning(txInfo);
            return result;
        }
    }

程序执行的是最后的else分支，步骤很清晰

1.获取 TransactionAttribute

2.基于TransactionAttribute获取TransactionManager

3.基于TransactionAttribute获取 joinpointIdentification(没研究什么作用)

4. 基于1,2,3创建的对象获取  TransactionAspectSupport.TransactionInfo，transactionInfo是TransactionAspectSupport的一个内部类

5.执行业务方法

6.抓到异常就回滚，并清除事务，然后向上抛异常；没有异常就清除事务，然后提交

对象之间的关联关系

3.各个对象的获取

TransactionManager的获取比较简单，程序里获取到的其实就是自己配置的bean

创建TransactionInfo的过程中要先获取TransactionStatus，TransactionStatus又需要拿到ConnectionHolder

3.1 createTransactionIfNecessary

org.springframework.transaction.interceptor.TransactionAspectSupport#createTransactionIfNecessary

protected TransactionAspectSupport.TransactionInfo createTransactionIfNecessary(@Nullable PlatformTransactionManager tm, @Nullable TransactionAttribute txAttr, final String joinpointIdentification) {
        if (txAttr != null && ((TransactionAttribute)txAttr).getName() == null) {
            txAttr = new DelegatingTransactionAttribute((TransactionAttribute)txAttr) {
                public String getName() {
                    return joinpointIdentification;
                }
            };
        }

        TransactionStatus status = null;
        if (txAttr != null) {
            if (tm != null) {
                status = tm.getTransaction((TransactionDefinition)txAttr);
            } else if (this.logger.isDebugEnabled()) {
                this.logger.debug("Skipping transactional joinpoint [" + joinpointIdentification + "] because no transaction manager has been configured");
            }
        }

        return this.prepareTransactionInfo(tm, (TransactionAttribute)txAttr, joinpointIdentification, status);
    }

3.2 获取TransactionStatus

这里先调用   status = tm.getTransaction((TransactionDefinition)txAttr)  创建TransactionStatus

org.springframework.transaction.support.AbstractPlatformTransactionManager#getTransaction

public final TransactionStatus getTransaction(@Nullable TransactionDefinition definition) throws TransactionException {
        Object transaction = this.doGetTransaction();
        boolean debugEnabled = this.logger.isDebugEnabled();
        if (definition == null) {
            definition = new DefaultTransactionDefinition();
        }

        if (this.isExistingTransaction(transaction)) {
            return this.handleExistingTransaction((TransactionDefinition)definition, transaction, debugEnabled);
        } else if (((TransactionDefinition)definition).getTimeout() < -1) {
            throw new InvalidTimeoutException("Invalid transaction timeout", ((TransactionDefinition)definition).getTimeout());
        } else if (((TransactionDefinition)definition).getPropagationBehavior() == 2) {
            throw new IllegalTransactionStateException("No existing transaction found for transaction marked with propagation 'mandatory'");
        } else if (((TransactionDefinition)definition).getPropagationBehavior() != 0 && ((TransactionDefinition)definition).getPropagationBehavior() != 3 && ((TransactionDefinition)definition).getPropagationBehavior() != 6) {
            if (((TransactionDefinition)definition).getIsolationLevel() != -1 && this.logger.isWarnEnabled()) {
                this.logger.warn("Custom isolation level specified but no actual transaction initiated; isolation level will effectively be ignored: " + definition);
            }

            boolean newSynchronization = this.getTransactionSynchronization() == 0;
            return this.prepareTransactionStatus((TransactionDefinition)definition, (Object)null, true, newSynchronization, debugEnabled, (Object)null);
        } else {
            AbstractPlatformTransactionManager.SuspendedResourcesHolder suspendedResources = this.suspend((Object)null);
            if (debugEnabled) {
                this.logger.debug("Creating new transaction with name [" + ((TransactionDefinition)definition).getName() + "]: " + definition);
            }

            try {
                boolean newSynchronization = this.getTransactionSynchronization() != 2;
                DefaultTransactionStatus status = this.newTransactionStatus((TransactionDefinition)definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
                this.doBegin(transaction, (TransactionDefinition)definition);
                this.prepareSynchronization(status, (TransactionDefinition)definition);
                return status;
            } catch (Error | RuntimeException var7) {
                this.resume((Object)null, suspendedResources);
                throw var7;
            }
        }
    }

3.3 获取transactionStatus前先获取DataSourceTransactionObject

程序最上面: Object transaction = this.doGetTransaction();　创建DataSourceTransactionObject对象，这是DataSourceTransactionManager的内部类

org.springframework.jdbc.datasource.DataSourceTransactionManager#doGetTransaction

protected Object doGetTransaction() {
    DataSourceTransactionManager.DataSourceTransactionObject txObject = new DataSourceTransactionManager.DataSourceTransactionObject();
    txObject.setSavepointAllowed(this.isNestedTransactionAllowed());
    ConnectionHolder conHolder = (ConnectionHolder)TransactionSynchronizationManager.getResource(this.obtainDataSource());
    txObject.setConnectionHolder(conHolder, false);
    return txObject;
}

这里还获取了ConnectionHolder对象，这里newConnectionHolder为false

获取的方法如下:

org.springframework.transaction.support.TransactionSynchronizationManager#getResource

@Nullable
public static Object getResource(Object key) {
    Object actualKey = TransactionSynchronizationUtils.unwrapResourceIfNecessary(key);
    Object value = doGetResource(actualKey);
    if (value != null && logger.isTraceEnabled()) {
        logger.trace("Retrieved value [" + value + "] for key [" + actualKey + "] bound to thread [" + Thread.currentThread().getName() + "]");
    }
    return value;
}

看代码很有意思，好像是通过一个key获取的，类似于从一个池子里面拿东西一样，其实当A方法执行的时候并没有获取到ConnectionHolder，拿到的是null

org.springframework.transaction.support.TransactionSynchronizationManager#doGetResource

private static Object doGetResource(Object actualKey) {
    Map<Object, Object> map = (Map)resources.get();
    if (map == null) {
        return null;
    } else {
        Object value = map.get(actualKey);
        if (value instanceof ResourceHolder && ((ResourceHolder)value).isVoid()) {
            map.remove(actualKey);
            if (map.isEmpty()) {
                resources.remove();
            }

            value = null;
        }

        return value;
    }
}

resources对象其实是一个ThreadLocal，意思是同一个线程中拿到的ConnectionHolder是相同的

3.3 doBegin方法

org.springframework.jdbc.datasource.DataSourceTransactionManager#doBegin

protected void doBegin(Object transaction, TransactionDefinition definition) {
    DataSourceTransactionManager.DataSourceTransactionObject txObject = (DataSourceTransactionManager.DataSourceTransactionObject)transaction;
    Connection con = null;

    try {
        if (!txObject.hasConnectionHolder() || txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
            Connection newCon = this.obtainDataSource().getConnection();
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
            }

            txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
        }

        txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
        con = txObject.getConnectionHolder().getConnection();
        Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
        txObject.setPreviousIsolationLevel(previousIsolationLevel);
        if (con.getAutoCommit()) {
            txObject.setMustRestoreAutoCommit(true);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
            }

            con.setAutoCommit(false);
        }

        this.prepareTransactionalConnection(con, definition);
        txObject.getConnectionHolder().setTransactionActive(true);
        int timeout = this.determineTimeout(definition);
        if (timeout != -1) {
            txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
        }

        if (txObject.isNewConnectionHolder()) {
            TransactionSynchronizationManager.bindResource(this.obtainDataSource(), txObject.getConnectionHolder());
        }

    } catch (Throwable var7) {
        if (txObject.isNewConnectionHolder()) {
            DataSourceUtils.releaseConnection(con, this.obtainDataSource());
            txObject.setConnectionHolder((ConnectionHolder)null, false);
        }

        throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", var7);
    }
}

截取该方法的重要几行:

Connection newCon = this.obtainDataSource().getConnection();
if (this.logger.isDebugEnabled()) {
    this.logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
}

txObject.setConnectionHolder(new ConnectionHolder(newCon), true);

先获取连接(java.sql.Connection)，然后创建ConnectionHolder，newConnectionHolder设置为true，如果之前已经不为空了,newConnectionHolder就为false

如果newConnectionHolder 为 true，还需要将 connectionHolder放到threadLocal里面，让后面的方法可以获取到相同的ConnectionHolder，截取的代码如下:

if (txObject.isNewConnectionHolder()) {
    TransactionSynchronizationManager.bindResource(this.obtainDataSource(), txObject.getConnectionHolder());
}

到这里TransactionStatus就创建好了

3.3 获取TransactionInfo

org.springframework.transaction.interceptor.TransactionAspectSupport#prepareTransactionInfo

protected TransactionAspectSupport.TransactionInfo prepareTransactionInfo(@Nullable PlatformTransactionManager tm, @Nullable TransactionAttribute txAttr, String joinpointIdentification, @Nullable TransactionStatus status) {
    TransactionAspectSupport.TransactionInfo txInfo = new TransactionAspectSupport.TransactionInfo(tm, txAttr, joinpointIdentification);
    if (txAttr != null) {
        if (this.logger.isTraceEnabled()) {
            this.logger.trace("Getting transaction for [" + txInfo.getJoinpointIdentification() + "]");
        }

        txInfo.newTransactionStatus(status);
    } else if (this.logger.isTraceEnabled()) {
        this.logger.trace("Don't need to create transaction for [" + joinpointIdentification + "]: This method isn't transactional.");
    }

    txInfo.bindToThread();
    return txInfo;
}

细看 txInfo.bindToThread();

org.springframework.transaction.interceptor.TransactionAspectSupport.TransactionInfo#bindToThread

private void bindToThread() {
    this.oldTransactionInfo = (TransactionAspectSupport.TransactionInfo)TransactionAspectSupport.transactionInfoHolder.get();
    TransactionAspectSupport.transactionInfoHolder.set(this);
}

java.lang.ThreadLocal#get 

public T get() {
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null) {
        ThreadLocalMap.Entry e = map.getEntry(this);
        if (e != null) {
            @SuppressWarnings("unchecked")
            T result = (T)e.value;
            return result;
        }
    }
    return setInitialValue();
}

bindToThread()的的作用是获取oldTransactionInfo，还有线程有关(具体原理未知)

４.B方法抛异常后的回滚操作

org.springframework.transaction.interceptor.TransactionAspectSupport#completeTransactionAfterThrowing

protected void completeTransactionAfterThrowing(@Nullable TransactionAspectSupport.TransactionInfo txInfo, Throwable ex) {
    if (txInfo != null && txInfo.getTransactionStatus() != null) {
        if (this.logger.isTraceEnabled()) {
            this.logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() + "] after exception: " + ex);
        }

        if (txInfo.transactionAttribute != null && txInfo.transactionAttribute.rollbackOn(ex)) {
            try {
                txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
            } catch (TransactionSystemException var6) {
                this.logger.error("Application exception overridden by rollback exception", ex);
                var6.initApplicationException(ex);
                throw var6;
            } catch (Error | RuntimeException var7) {
                this.logger.error("Application exception overridden by rollback exception", ex);
                throw var7;
            }
        } else {
            try {
                txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
            } catch (TransactionSystemException var4) {
                this.logger.error("Application exception overridden by commit exception", ex);
                var4.initApplicationException(ex);
                throw var4;
            } catch (Error | RuntimeException var5) {
                this.logger.error("Application exception overridden by commit exception", ex);
                throw var5;
            }
        }
    }

}

txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());调用transactionManager进行rollback

org.springframework.transaction.support.AbstractPlatformTransactionManager#rollback

public final void rollback(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");
    } else {
        DefaultTransactionStatus defStatus = (DefaultTransactionStatus)status;
        this.processRollback(defStatus, false);
    }
}

进一步调自身的processRollback

org.springframework.transaction.support.AbstractPlatformTransactionManager#processRollback

private void processRollback(DefaultTransactionStatus status, boolean unexpected) {
    try {
        boolean unexpectedRollback = unexpected;

        try {
            this.triggerBeforeCompletion(status);
            if (status.hasSavepoint()) {
                if (status.isDebug()) {
                    this.logger.debug("Rolling back transaction to savepoint");
                }

                status.rollbackToHeldSavepoint();
            } else if (status.isNewTransaction()) {
                if (status.isDebug()) {
                    this.logger.debug("Initiating transaction rollback");
                }

                this.doRollback(status);
            } else {
                if (status.hasTransaction()) {
                    if (!status.isLocalRollbackOnly() && !this.isGlobalRollbackOnParticipationFailure()) {
                        if (status.isDebug()) {
                            this.logger.debug("Participating transaction failed - letting transaction originator decide on rollback");
                        }
                    } else {
                        if (status.isDebug()) {
                            this.logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
                        }

                        this.doSetRollbackOnly(status);
                    }
                } else {
                    this.logger.debug("Should roll back transaction but cannot - no transaction available");
                }

                if (!this.isFailEarlyOnGlobalRollbackOnly()) {
                    unexpectedRollback = false;
                }
            }
        } catch (Error | RuntimeException var8) {
            this.triggerAfterCompletion(status, 2);
            throw var8;
        }

        this.triggerAfterCompletion(status, 1);
        if (unexpectedRollback) {
            throw new UnexpectedRollbackException("Transaction rolled back because it has been marked as rollback-only");
        }
    } finally {
        this.cleanupAfterCompletion(status);
    }

}

this.triggerBeforeCompletion(status)　这个方法好像释放了连接

B不是新事务，所以最后会执行  this.doSetRollbackOnly(status);

org.springframework.jdbc.datasource.DataSourceTransactionManager#doSetRollbackOnly

protected void doSetRollbackOnly(DefaultTransactionStatus status) {
    DataSourceTransactionManager.DataSourceTransactionObject txObject = (DataSourceTransactionManager.DataSourceTransactionObject)status.getTransaction();
    if (status.isDebug()) {
        this.logger.debug("Setting JDBC transaction [" + txObject.getConnectionHolder().getConnection() + "] rollback-only");
    }

    txObject.setRollbackOnly();
}

org.springframework.jdbc.datasource.DataSourceTransactionManager.DataSourceTransactionObject#setRollbackOnly

public void setRollbackOnly() {
    this.getConnectionHolder().setRollbackOnly();
}

这里可以看到最终设置的是connectionHolder的rollbackonly属性

5.A方法尝试提交时的操作

org.springframework.transaction.interceptor.TransactionAspectSupport#commitTransactionAfterReturning

protected void commitTransactionAfterReturning(@Nullable TransactionAspectSupport.TransactionInfo txInfo) {
    if (txInfo != null && txInfo.getTransactionStatus() != null) {
        if (this.logger.isTraceEnabled()) {
            this.logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() + "]");
        }

        txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
    }

}

同样的，这里调用transactionManager进行提交

org.springframework.transaction.support.AbstractPlatformTransactionManager#commit

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");
    } else {
        DefaultTransactionStatus defStatus = (DefaultTransactionStatus)status;
        if (defStatus.isLocalRollbackOnly()) {
            if (defStatus.isDebug()) {
                this.logger.debug("Transactional code has requested rollback");
            }

            this.processRollback(defStatus, false);
        } else if (!this.shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
            if (defStatus.isDebug()) {
                this.logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
            }

            this.processRollback(defStatus, true);
        } else {
            this.processCommit(defStatus);
        }
    }
}

这个方法判断了一些无法提交的情况，程序这里走第二个分支，部分代码如下:

else if (!this.shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
    if (defStatus.isDebug()) {
        this.logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
    }

    this.processRollback(defStatus, true);
}

判断条件为:　

1.全局不是rollbackonly的时候也提交(这个可能是一个配置的参数，配合在rollbackonly的时候也提交，也就是出现现在这种情况后，不用回滚，直接提交)   

2.并且全局是rollbackonly

org.springframework.transaction.support.DefaultTransactionStatus#isGlobalRollbackOnly

public boolean isGlobalRollbackOnly() {
    return this.transaction instanceof SmartTransactionObject && ((SmartTransactionObject)this.transaction).isRollbackOnly();
}

这里又要满足两个条件

1 .这里的transaction是DataSourceTransactionObject

DataSourceTransaction继承 JdbcTransactionObjectSupport

JdbcTransactionObjectSupport又实现 SmartTransactionObject，所以第一个条件满足

2. DatSourceTransactionObject的 RollbackOnly 的get和set方法如下

public void setRollbackOnly() {
    this.getConnectionHolder().setRollbackOnly();
}

public boolean isRollbackOnly() {
    return this.getConnectionHolder().isRollbackOnly();
}

之前B方法抛出异常的时候，就是调用的DataSourceTransactionObject的set方法设置rollbackonly为true，现在再用get方法获取，只要是同一个connectionHolder，A获取到的rollbackOnly就是true，就会触发回滚，执行   this.processRollback(defStatus, true);

org.springframework.transaction.support.AbstractPlatformTransactionManager#processRollback

private void processRollback(DefaultTransactionStatus status, boolean unexpected) {
    try {
        boolean unexpectedRollback = unexpected;

        try {
            this.triggerBeforeCompletion(status);
            if (status.hasSavepoint()) {
                if (status.isDebug()) {
                    this.logger.debug("Rolling back transaction to savepoint");
                }

                status.rollbackToHeldSavepoint();
            } else if (status.isNewTransaction()) {
                if (status.isDebug()) {
                    this.logger.debug("Initiating transaction rollback");
                }

                this.doRollback(status);
            } else {
                if (status.hasTransaction()) {
                    if (!status.isLocalRollbackOnly() && !this.isGlobalRollbackOnParticipationFailure()) {
                        if (status.isDebug()) {
                            this.logger.debug("Participating transaction failed - letting transaction originator decide on rollback");
                        }
                    } else {
                        if (status.isDebug()) {
                            this.logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
                        }

                        this.doSetRollbackOnly(status);
                    }
                } else {
                    this.logger.debug("Should roll back transaction but cannot - no transaction available");
                }

                if (!this.isFailEarlyOnGlobalRollbackOnly()) {
                    unexpectedRollback = false;
                }
            }
        } catch (Error | RuntimeException var8) {
            this.triggerAfterCompletion(status, 2);
            throw var8;
        }

        this.triggerAfterCompletion(status, 1);
        if (unexpectedRollback) {
            throw new UnexpectedRollbackException("Transaction rolled back because it has been marked as rollback-only");
        }
    } finally {
        this.cleanupAfterCompletion(status);
    }

}

到这里  unexpectedRollback为true，就抛出了  "Transaction rolled back because it has been marked as rollback-only"这个异常了