ClassCastException after upgrading from Spring Boot 2.1.9 to 2.2.1 (Spring Integration) - spring

Question

I have a Spring Boot project that uses Spring Integration. I upgraded from Spring Boot 2.1.9.RELEASE to 2.2.1.RELEASE and now I get an exception when my application starts up.
The exception is logged at DEBUG level and my application still seems to work without problems.
Is this a bug in the new version of Spring Integration?
Stack trace:
2019-11-09 11:57:28.983 DEBUG 12776 --- [ restartedMain] o.s.i.h.s.MessagingMethodInvokerHelper : Exception trying to extract interface
java.lang.ClassCastException: class com.demo.mail.ConfirmationMailTransformer cannot be cast to class org.springframework.aop.framework.Advised (com.demo.mail.ConfirmationMailTransformer is in unnamed module of loader org.springframework.boot.devtools.restart.classloader.RestartClassLoader #24ed52ef; org.springframework.aop.framework.Advised is in unnamed module of loader 'app')
at org.springframework.integration.handler.support.MessagingMethodInvokerHelper.getTargetClass(MessagingMethodInvokerHelper.java:985) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.handler.support.MessagingMethodInvokerHelper.findHandlerMethodsForTarget(MessagingMethodInvokerHelper.java:711) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.handler.support.MessagingMethodInvokerHelper.<init>(MessagingMethodInvokerHelper.java:294) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.handler.support.MessagingMethodInvokerHelper.<init>(MessagingMethodInvokerHelper.java:215) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.handler.support.MessagingMethodInvokerHelper.<init>(MessagingMethodInvokerHelper.java:219) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.handler.MethodInvokingMessageProcessor.<init>(MethodInvokingMessageProcessor.java:54) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.transformer.MethodInvokingTransformer.<init>(MethodInvokingTransformer.java:43) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.config.TransformerFactoryBean.createMethodInvokingHandler(TransformerFactoryBean.java:53) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.config.AbstractStandardMessageHandlerFactoryBean.createHandler(AbstractStandardMessageHandlerFactoryBean.java:142) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.config.AbstractSimpleMessageHandlerFactoryBean.createHandlerInternal(AbstractSimpleMessageHandlerFactoryBean.java:198) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.config.AbstractSimpleMessageHandlerFactoryBean.getObject(AbstractSimpleMessageHandlerFactoryBean.java:186) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.integration.config.AbstractSimpleMessageHandlerFactoryBean.getObject(AbstractSimpleMessageHandlerFactoryBean.java:60) ~[spring-integration-core-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:171) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:135) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:377) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:127) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveManagedList(BeanDefinitionValueResolver.java:427) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:173) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1706) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1451) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:879) ~[spring-beans-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.1.RELEASE.jar:5.2.1.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at com.demo.DemoApplication.main(DemoApplication.java:12) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.2.1.RELEASE.jar:2.2.1.RELEASE]
This is what my class ConfirmationMailTransformer looks like:
package com.demo.mail;
import com.demo.model.RegistrationEvent;
import org.springframework.stereotype.Component;
#Component
public class ConfirmationMailTransformer {
public String toMailText(RegistrationEvent event) {
return "Email text";
}
}
It's configured using Spring Integration XML configuration:
<!-- Transform payload to text to be used as the body of the e-mail -->
<int:transformer ref="confirmationMailTransformer" method="toMailText"/>
Java version (AdoptOpenJDK 11 on Ubuntu 18.04):
openjdk version "11.0.4" 2019-07-16
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.4+11)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.4+11, mixed mode)
Plain Spring Boot application generated from https://start.spring.io with Spring Boot starter for Spring Integration, running with mvn spring-boot:run

Answer 1

Judging by "unnamed module" in the exception message, you are using Java's module system. Judging by RestartClassLoader in the exception message, you are using Spring Boot's DevTools. At the time of writing, this combination is unsupported and known not to work. There's an open enhancement request that you may want to subscribe to.
Regardless of the possibly unsupported combination of the module system and DevTools, the change in behaviour appears to be due to this commit in Spring Integration. Previously, there was a check for AopUtils.isAopProxy(targetObject) being true before an attempt to cast to Advised was made. This check is no longer made. That should be benign although slightly ugly if you have debug logging enabled. You may want to raise a Spring Integration issue so that the team can investigate and reinstate the check if needed.