当我使用Spring aop时，@target注释不起作用

Question

当我在spring aop拦截类上使用注释时，我使用了@target limit匹配方法。但调试时，会提示以下错误。

org.springframework.context.ApplicationContextException: Unable to start embedded container; nested exception is org.springframework.boot.context.embedded.EmbeddedServletContainerException: Unable to start embedded Tomcat
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:138)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:536)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:123)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:666)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:353)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:300)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1082)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1071)
    at com.example.springbootdemo.SpringbootdemoApplication.main(SpringbootdemoApplication.java:20)
Caused by: org.springframework.boot.context.embedded.EmbeddedServletContainerException: Unable to start embedded Tomcat
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.initialize(TomcatEmbeddedServletContainer.java:135)
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainer.<init>(TomcatEmbeddedServletContainer.java:87)
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.getTomcatEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:535)
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory.getEmbeddedServletContainer(TomcatEmbeddedServletContainerFactory.java:177)
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory$$FastClassBySpringCGLIB$$bc74f446.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:736)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:173)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:671)
    at org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory$$EnhancerBySpringCGLIB$$bda70dbb.getEmbeddedServletContainer(<generated>)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.createEmbeddedServletContainer(EmbeddedWebApplicationContext.java:162)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh(EmbeddedWebApplicationContext.java:135)
    ... 8 common frames omitted
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'metricsFilter' defined in class path resource [org/springframework/boot/actuate/autoconfigure/MetricFilterAutoConfiguration.class]: Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class org.springframework.boot.actuate.autoconfigure.MetricsFilter: 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.actuate.autoconfigure.MetricsFilter
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:562)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:481)
    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:202)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.getOrderedBeansOfType(ServletContextInitializerBeans.java:212)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAsRegistrationBean(ServletContextInitializerBeans.java:165)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAsRegistrationBean(ServletContextInitializerBeans.java:160)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.addAdaptableBeans(ServletContextInitializerBeans.java:145)
    at org.springframework.boot.web.servlet.ServletContextInitializerBeans.<init>(ServletContextInitializerBeans.java:78)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.getServletContextInitializerBeans(EmbeddedWebApplicationContext.java:240)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.selfInitialize(EmbeddedWebApplicationContext.java:214)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.access$000(EmbeddedWebApplicationContext.java:91)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext$1.onStartup(EmbeddedWebApplicationContext.java:205)
    at org.springframework.boot.context.embedded.tomcat.TomcatStarter.onStartup(TomcatStarter.java:53)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5154)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1412)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1402)
    at java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:266)
    at java.util.concurrent.FutureTask.run(FutureTask.java)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:748)
Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class org.springframework.boot.actuate.autoconfigure.MetricsFilter: 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.actuate.autoconfigure.MetricsFilter
    at org.springframework.aop.framework.CglibAopProxy.getProxy(CglibAopProxy.java:209)
    at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:109)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.createProxy(AbstractAutoProxyCreator.java:463)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:346)
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:295)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:421)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1634)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
    ... 24 common frames omitted
Caused by: java.lang.IllegalArgumentException: Cannot subclass final class org.springframework.boot.actuate.autoconfigure.MetricsFilter
    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:1001)
    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$$$capture(FutureTask.java:266)
    at java.util.concurrent.FutureTask.run(FutureTask.java)
    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:54)
    at org.springframework.aop.framework.CglibAopProxy.getProxy(CglibAopProxy.java:201)
    ... 31 common frames omitted

我的切入点是这样的

@Pointcut("@target(com.example.springbootdemo.aspect.TimeIt)")
public void calcTime() {}

其中TimeIt是注释：

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE,ElementType.METHOD})
public @interface TimeIt {
    boolean enabled() default true;
}

我把切点改成能跑了

@Pointcut("@within(com.example.springbootdemo.aspect.TimeIt)")
public void calcTime() {}

我不太理解的是，MetricsFilter 类没有这个注释，那么为什么要生成代理呢？任何人都可以帮我吗？谢谢。

Answer 1

我无法运行您的代码，因为您只提供了几个小片段，但我注意到的是：

• 至于SpringAOP和AspectJ中@target（）和@within（）之间的区别，请在此处查看我的答案。
• 您的注释具有@Target（{元素类型.TYPE， 元素类型.METHOD}），但您的两个切入点都只针对带注释的类型，而不是注释方法。为此，您需要使用@annotation。也就是说，您的注释方法永远不会与此切入相匹配，因此建议永远不会触发。
• 你的例外必须来自另一个切入点/建议对，而不是你在问题中显示的那些 - 可能是全局性的，如执行（* *（.））或内部（*）或目标（*），它们将尝试编织成各种Spring组件，包括你自己的和内部的。所以你需要将另一个切入限制在类似执行的东西（* my.base.包..*(..))或内部（我的基地包装。*） 或目标（我的基地包装。*） 或至少排除您不希望通过 ！within 拦截的内部Spring包（组织.Spring框架..*).