Default CGLib proxy setting default cannot be overridden by using core framework annotations (@EnableTransactionManagement, @EnableAspectJAutoProxy)

[odrotbohm]

Spring Boot 2.0 changes the default value for the configuration property spring.aop.proxy-target-class to true if nothing is configured. This causes an explicit @EnableAspectJAutoProxy(proxy-target-class = false) not being picked up anymore. Also an explicit @EnableTransactionManagement(proxy-target-class = false) is not causing transactional proxies being created as JDK proxies anymore as the default true gets applied.

I.e. you see the same symptoms as described in #8434.

[wilkinsona]

Also an explicit @EnableTransactionManagement(proxy-target-class = false) is not causing transactional proxies being created as JDK proxies anymore as the default true gets applied.

We have a test that disagrees with this statement. I think the problem is purely in CglibAutoProxyConfiguration. Use of CGLib proxies is an application-context-wide switch so if CgLibAutoProxyConfiguration forces CGLib proxies then whatever EnableTransactionManagementConfiguration does will not make any difference.

I'll update AopAutoConfiguration to back off if the auto-proxy creator bean already exists. That will mean that specifying both @EnableTransactionManagement and @EnableAspectJAutoProxy will switch off CGLib proxies. Alternatively, you can configure both with a single property: spring.aop.proxy-target-class.

[odrotbohm]

We have a test that disagrees with this statement.

Find this demo project showing that @EnableTransactionManagement(proxyTargetClass = false) still creates CGLib proxies for classes annotated with @Transactional: demo-3.zip.

My extended inspection of also @ EnableAspectJAutoProxy was caused by my debug attempts not revealing any transaction specific components being involved but only a generic AnnotationAwareAspectJAutoProxyCreator that made me think the changed defaults might now require also @EnableAspectJAutoProxy(proxyTargetClass = true).

From a user point of view, I'd like to see explicit configuration using core Spring Framework means take precedence over Spring Boot defaults.

[wilkinsona]

I'll update AopAutoConfiguration to back off if the auto-proxy creator bean already exists.

Unfortunately, it's not as simple as that. The problem is that we're fighting against three different ways in the Framework that the proxy type can be configured:

1. @EnableAspectJAutoProxy
2. @EnableCaching
3. @EnableTransactionManagement

Use of any of the three will define the org.springframework.aop.config.internalAutoProxyCreator bean. If we change AopAutoConfiguration to back off in the presence of that bean, using any of the three annotations above will stop spring.aop.proxy-target-class from having an effect.

Generally speaking, 1 and 3 aren't needed in a Boot app, so they are perhaps not too bad. However, 2 is required if you want to enable caching. We have no way of distinguishing between a user that just wants to enable caching and a user that wants to enable caching and override the type of proxies that are created.

Given the above, I don't think we can do anything that would allow us to override the default using Framework's annotations. Instead, we really need to use a single context-wide switch to control the type of proxies that are created. We already have that switch in the form of the spring.aop.proxy-target-class.

While looking at this issue I found some discrepancies in our javadoc and documentation. I've opened #12196 to take care of those.