How to resolve org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class

Jan 27, 2025

Cowrie

Dev @ Bswen

1. The purpose of this post

This post demonstrates how to resolve the org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class exception when using @Autowired in Spring.

Exception

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myService': Injection of autowired dependencies failed; nested exception is org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class java8.learn.autowire.MyObject]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Cannot subclass final class java8.learn.autowire.MyObject
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:372) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1268) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) [spring-boot-1.5.12.RELEASE.jar:1.5.12.RELEASE]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) [spring-boot-1.5.12.RELEASE.jar:1.5.12.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) [spring-boot-1.5.12.RELEASE.jar:1.5.12.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) [spring-boot-1.5.12.RELEASE.jar:1.5.12.RELEASE]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) [spring-boot-1.5.12.RELEASE.jar:1.5.12.RELEASE]
        at java8.learn.TestJava8App.main(TestJava8App.java:18) [classes/:na]
Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class java8.learn.autowire.MyObject]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Cannot subclass final class java8.learn.autowire.MyObject
        at org.springframework.aop.framework.CglibAopProxy.getProxy(CglibAopProxy.java:211) ~[spring-aop-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:109) ~[spring-aop-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver.buildLazyResolutionProxy(ContextAnnotationAutowireCandidateResolver.java:115) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver.getLazyResolutionProxyIfNecessary(ContextAnnotationAutowireCandidateResolver.java:50) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1063) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        ... 16 common frames omitted
Caused by: java.lang.IllegalArgumentException: Cannot subclass final class java8.learn.autowire.MyObject
        at org.springframework.cglib.proxy.Enhancer.generateClass(Enhancer.java:565) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.transform.TransformingClassGenerator.generateClass(TransformingClassGenerator.java:33) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.aop.framework.CglibAopProxy$ClassLoaderAwareUndeclaredThrowableStrategy.generate(CglibAopProxy.java:999) ~[spring-aop-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:329) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.proxy.Enhancer.generate(Enhancer.java:492) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:93) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:91) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_121]
        at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:116) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:291) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.proxy.Enhancer.createHelper(Enhancer.java:480) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.cglib.proxy.Enhancer.createClass(Enhancer.java:337) ~[spring-core-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.aop.framework.ObjenesisCglibAopProxy.createProxyClassAndInstance(ObjenesisCglibAopProxy.java:55) ~[spring-aop-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        at org.springframework.aop.framework.CglibAopProxy.getProxy(CglibAopProxy.java:201) ~[spring-aop-4.3.16.RELEASE.jar:4.3.16.RELEASE]
        ... 23 common frames omitted

2. Environments

• Java 1.8+
• Spring Framework 4+

3. The Code

The object to be autowired:

MyObject.java

@Component
public final class MyObject {
    public String getTime() {
        return (new Date()).toString();
    }
}

The class is final because I don’t want others to override its methods. However, when I use @Autowired and @Lazy in other classes like this:

Usage

@Autowired @Lazy
private MyObject myObject;

Running the application results in the above exception.

Key Concept

Spring uses CGLIB to generate a subclass of the @Lazy class. If the class is marked as final, CGLIB cannot subclass it, leading to the AopConfigException.

To resolve this issue, I modified the code by removing the final modifier:

Modified

@Component
public class MyObject { // Removed final
    public String getTime() {
        return (new Date()).toString();
    }
}

After cleaning and re-running the application, everything works as expected.

Important Tip

If you encounter AopConfigException in Spring, check if the class being proxied is final. Removing the final modifier is often the simplest solution.

4. Summary

In this post, we explored how to resolve the AopConfigException in Spring when using @Autowired and @Lazy annotations. The primary cause of this exception is attempting to proxy a final class, which CGLIB cannot subclass. By removing the final modifier from the class, the issue is resolved, and the application runs smoothly. Always ensure that classes intended for proxying are not marked as final.

Final Words + More Resources

My intention with this article was to help others who might be considering solving such a problem. So I hope that’s been the case here. If you still have any questions, don’t hesitate to ask me by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

• 👨‍💻 Spring Framework Documentation

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!

Tags:

• java
• spring

How to resolve 'missing : in substitution' when building docker image

Linux shell command to start, stop(kill) or restart springboot executable jar applications