Cannot downgrade to Spring Framework for CGLIB NullPointerException issue

[breun]

While upgrading to Spring Boot 3.4.3, I ran into this Spring Framework 6.2.3 issue while running tests: NullPointerException thrown when ConfigurationClassEnhancer creates CGLIB proxy.

As a temporary workaround, I tried overriding spring-framework.version to 6.2.2, but that results in 'method not found' errors, so it seems that Spring Boot 3.4.3 is not compatible with the previous Spring Framework patch release.

The same issue also seems to be present in Spring Framework 6.1.17, affecting Spring Boot 3.3.9.

I don't know if this affects a significant number of users, but it seems that this Spring Framework bug is currently a blocker for upgrading to the latest versions of Spring Boot.

[bclozel]

As a temporary workaround, I tried overriding spring-framework.version to 6.2.2, but that results in 'method not found' errors, so it seems that Spring Boot 3.4.3 is not compatible with the previous Spring Framework patch release.

Can you provide a stacktrace for that?

[k-seth]

I decided to give downgrading Spring Framework (as the issue opener discussed) a try in a project with similar issues, and the stack trace regarding a missing method includes:

 Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.autoconfigure.metrics.cache.CacheMetricsRegistrarConfiguration]: Constructor threw exception
 	at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:222)
 	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:145)
 	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:318)
 	... 120 more
 Caused by: java.lang.NoSuchMethodError: 'java.util.Map org.springframework.beans.factory.support.SimpleAutowireCandidateResolver.resolveAutowireCandidates(org.springframework.beans.factory.config.ConfigurableListableBeanFactory, java.lang.Class)'
 	at org.springframework.boot.actuate.autoconfigure.metrics.cache.CacheMetricsRegistrarConfiguration.<init>(CacheMetricsRegistrarConfiguration.java:57)
 	at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:62)
 	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:502)
 	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:486)
 	at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:209)
 	... 122 more

The use of the resolveAutowireCandidates seems to be sprinkled through a handful of actuator configurations, introduced in 4cb9d81

[bclozel]

Thanks for the information @k-seth ; unfortunately I don't see how we can reinstate compatibility with the previous Framework version without breaking #43481. Out of curiosity @breun @k-seth could you check whether Spring Framework 6.2.4-SNAPSHOT really fixes the problem for you?

[bclozel]

In the meantime, I don't see anything actionable here, as we don't support Framework downgrades from a Boot perspective (it might work, but we don't guarantee this). In the meantime, you can downgrade to the latest Spring Boot maintenance version that works for you.
Please follow up on the Framework issue if you get a chance to test SNAPSHOTs. This would help us refine the fix if needed, as this one is tricky to reproduce in the first place as far as I understand.