Transaction rolled back because it has been marked as rollback-only-蒲公英云

Transaction rolled back because it has been marked as rollback-only

spring 具备多种事务传播机制，最常用的是REQUIRED，即如果不存在事务，则新建一个事务；如果存在事务，则加入现存的事务中。
示例代码如下：

public void A() {
    querySomething(...)；
    try {
      B()
    } catch () {
    }
    saveSomethinf()；
}
public void B() {
    throw Exception()
}

此时B会和A存在一个事务中。如果B抛出异常没有捕获，即使在A中捕获并处理，仍会发生异常：Transaction rolled back because it has been marked as rollback-only
因为spring会在A捕获异常之前提前捕获到异常，并将当前事务设置为rollback-only，而A觉得对异常进行了捕获，它仍然继续commit，当TransactionManager发现状态为设置为rollback-only时，
则会抛出UnexpectedRollbackException
相关代码在AbstractPlatformTransactonManager.java中：

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);
            return;
        }
        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;
        }
        processCommit(defStatus);
    }