Lambda proxy generation fix causes BeanNotOfRequiredTypeException

[oliverlockwood]

I hit the problem described in #27971.

Rather than just adding the <argLine>--add-opens java.base/java.lang=ALL-UNNAMED</argLine> to my Surefire configuration, I decided to upgrade to Spring-Boot 2.6.4 (from 2.6.3) to take the fix that was described (because Spring-Boot 2.6.4 uses Spring framework version 5.3.16).

However, this led me to a different error, whereby we hit a org.springframework.beans.factory.BeanNotOfRequiredTypeException for the lambda bean, specifically:

org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'defaultMyThing' is expected to be of type 'com.oliverlockwood.MyThing' but was actually of type 'jdk.proxy2.$Proxy142'

At present, my not-so-pleasant options seem to come down to:

• Run under Java 17, using --add-opens JVM argument, and get stuck on Spring Boot 2.6.3 (not great)
• Run under Java 11 (not great), but be able to upgrade to Spring Boot 2.6.4
• Run under Java 17 and Spring Boot 2.6.4, but change the lambda beans to be explicit (not great).

I couldn't see a ticket representing this issue, and as Spring-Boot 2.6.4's only recently been released it is plausible that I might be the first person to hit this.

[sbrannen]

Hi @oliverlockwood,

Thanks for raising the issue. It may be a regression.

To help use analyze this, can you please provide a minimal sample application (or test class) that reproduces the BeanNotOfRequiredTypeException you are encountering (preferably as a Git repository that we can check out or a ZIP file that we can download and run)?

[oliverlockwood]

Yes @sbrannen.

I have created repo https://github.com/oliverlockwood/spring-framework-issue-28209 which demonstrates this clearly.

It turns out that the error case requires an AOP annotation to be applied to the interface being implemented (in this case, I've used @Retryable).

Please let me know if you need any further information, but I think it should now be pretty clear.

[sbrannen]

Thanks for creating the repo, @oliverlockwood. Much appreciated.

We'll look into it.

[sbrannen]

It turns out that the error case requires an AOP annotation to be applied to the interface being implemented (in this case, I've used @Retryable).

It's not because of the use of an annotation. Rather, the AOP advice for @Retryable makes use of an introduction (i.e., it introduces the org.springframework.retry.interceptor.Retryable marker interface to the proxy), and the fix for #27971 does not take this into account.

That's why the diagnostics generated by Spring Boot include the following.

The bean is of type 'jdk.proxy2.$Proxy64' and implements:
	org.springframework.retry.interceptor.Retryable
	org.springframework.aop.SpringProxy
	org.springframework.aop.framework.Advised
	org.springframework.core.DecoratingProxy

Here we see that org.springframework.retry.interceptor.Retryable is included in the set of interfaces implemented by the proxy, but the lambda interface (com.oliverlockwood.springframework.issue28209.ExampleInterface) is not.