1.背景

查了一下Spring文档，就是上面这段话所说的情况。

2.Spring官方文档有这么一段话

https://docs.spring.io/spring-framework/docs/current/reference/html/data-access.html#transaction-declarative

In proxy mode (which is the default), only external method calls coming in through the proxy are intercepted. This means that self-invocation (in effect, a method within the target object calling another method of the target object) does not lead to an actual transaction at runtime even if the invoked method is marked with @Transactional. Also, the proxy must be fully initialized to provide the expected behavior, so you should not rely on this feature in your initialization code — for example, in a @PostConstruct method.

我有一个Service类，

有一个方法会被当前类之外的类调用，称之为“A方法”，

A方法调用同一个类的另一个方法，称之为“B方法”，@Transactional注解加在B方法上面，

再来看官方文档的这句话，only external method calls coming in through the proxy are intercepted. 在这个例子中，A方法和B方法属于同一个类，同一个类的两个方法之间的调用，并没有“coming in through the proxy”，没有穿过Spring的动态代理。这样就根本没有形成Spring事务。

另外一个类的方法调用A方法，跨越了两个类，这样才是穿过了Spring的动态代理。

因此这里必须把@Transactional注解写在A方法上面。我这样修改了之后，事务就会回滚了，验证了Spring官方文档的这段话是正确的。