springaop問題——Cannot subclass final class org.springframework.boot.autoconfigure.AutoConfigurationPackages$BasePackages

問題描述：

在使用springaop對目標對象增強時，若切點的條件過於寬泛就會出現以下異常！

如：

@Before("execution(* *(..))")

@Before("args(..)")

@Before("within(org..*)")

...

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.autoconfigure.AutoConfigurationPackages': Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class org.springframework.boot.autoconfigure.AutoConfigurationPackages$BasePackages]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Cannot subclass final class org.springframework.boot.autoconfigure.AutoConfigurationPackages$BasePackages
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:564)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:761)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543)
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
	at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:120)
	at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:98)
	at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:116)
	... 26 common frames omitted
Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class org.springframework.boot.autoconfigure.AutoConfigurationPackages$BasePackages]: 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 org.springframework.boot.autoconfigure.AutoConfigurationPackages$BasePackages
	at org.springframework.aop.framework.CglibAopProxy.getProxy(CglibAopProxy.java:211)
	at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:109)
	at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.createProxy(AbstractAutoProxyCreator.java:466)
	at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:349)
	at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:298)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:423)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1634)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555)
	... 40 common frames omitted
Caused by: java.lang.IllegalArgumentException: Cannot subclass final class org.springframework.boot.autoconfigure.AutoConfigurationPackages$BasePackages
	at org.springframework.cglib.proxy.Enhancer.generateClass(Enhancer.java:565)
	at org.springframework.cglib.transform.TransformingClassGenerator.generateClass(TransformingClassGenerator.java:33)
	at org.springframework.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
	at org.springframework.aop.framework.CglibAopProxy$ClassLoaderAwareUndeclaredThrowableStrategy.generate(CglibAopProxy.java:999)
	at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:329)
	at org.springframework.cglib.proxy.Enhancer.generate(Enhancer.java:492)
	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:93)
	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData$3.apply(AbstractClassGenerator.java:91)
	at org.springframework.cglib.core.internal.LoadingCache$2.call(LoadingCache.java:54)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at org.springframework.cglib.core.internal.LoadingCache.createEntry(LoadingCache.java:61)
	at org.springframework.cglib.core.internal.LoadingCache.get(LoadingCache.java:34)
	at org.springframework.cglib.core.AbstractClassGenerator$ClassLoaderData.get(AbstractClassGenerator.java:116)
	at org.springframework.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:291)
	at org.springframework.cglib.proxy.Enhancer.createHelper(Enhancer.java:480)
	at org.springframework.cglib.proxy.Enhancer.createClass(Enhancer.java:337)
	at org.springframework.aop.framework.ObjenesisCglibAopProxy.createProxyClassAndInstance(ObjenesisCglibAopProxy.java:55)
	at org.springframework.aop.framework.CglibAopProxy.getProxy(CglibAopProxy.java:201)
	... 47 common frames omitted

 

問題分析：

通過異常信息可以看出，當spring通過cglib給目標對象org.springframework.boot.autoconfigure.AutoConfigurationPackages$BasePackages進行增強時，發生了異常。

 

原因：

1）cglib增強技術，是通過繼承原對象后動態創建子類來實現的。

2）通過查看BasePackages類源代碼，發現該類被final修飾。

static final class BasePackages {
	...
}

3）java不允許繼承被final所修飾的類。

 

解決方法：

以上問題出現的原因為aop定義的切點條件中，包含了被final所修飾的類。

1）通過修改類的訪問修飾符解決。

2）通過調整切點條件，過濾final修飾的類。