DemoMethodInterceptor类:
public class DemoMethodInterceptor implements MethodInterceptor { @Override public Object invoke(MethodInvocation invocation) throws Throwable { System.out.println("invoke start..."); return invocation.proceed(); } }
spring配置:
<bean id="demoMethodInterceptor" class="name.zhengwei.demo.spring.aop.DemoMethodInterceptor"> </bean> <bean class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator"> <property name="beanNames"> <value>class*</value> </property> <property name="interceptorNames"> <list> <value>demoMethodInterceptor</value> </list> </property> </bean>
这里用spring的BeanNameAutoProxyCreator来对以'class'作为前缀的bean做动态代理。结果抛出了异常,如下:
Error creating bean with name 'classA': Bean with name 'classA' has been injected into other beans [classB] in its raw version as part of a circular reference, but has eventually been wrapped. This means that said other beans do not use the final version of the bean. This is often the result of over-eager type matching - consider using 'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.
从提示看是非最终版本的classA被注入到了循环依赖的classB里,但spring是支持循环依赖的啊,而且在代码里不可避免会有这种情况出现,那为什么会出现非最终版本被注入呢?经过debug发现答案在,spring的‘AbstractAutowireCapableBeanFactory’的getEarlyBeanReference方法里( 我的spring版本是3.0.1-release)。
/** * Obtain a reference for early access to the specified bean, * typically for the purpose of resolving a circular reference. * @param beanName the name of the bean (for error handling purposes) * @param mbd the merged bean definition for the bean * @param bean the raw bean instance * @return the object to expose as bean reference */ protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) { Object exposedObject = bean; if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof SmartInstantiationAwareBeanPostProcessor) { SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp; exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName); } } } return exposedObject; }
如果spring设置为支持循环依赖(默认支持),那么在创建的时候,如果有循环依赖发生,就会执行上面这段代码。在DEBUG的时候发现了2个代理创建类,也就是InfrastructureAdvisorAutoProxyCreator(项目里用了spring-security)和BeanNameAutoProxyCreator,这两个类都会执行各自的getEarlyBeanReference方法,都来自父类AbstractAutoProxyCreator。
public Object getEarlyBeanReference(Object bean, String beanName) throws BeansException { Object cacheKey = getCacheKey(bean.getClass(), beanName); this.earlyProxyReferences.add(cacheKey); return wrapIfNecessary(bean, beanName, cacheKey); }
getEarlyBeanReference方法会缓存创建的代理对象,在各自this.earlyProxyReferences里,两个类都会创建代理,因此有了2个代理对象,前者先执行(InfrastructureAdvisorAutoProxyCreator),假设对象分别得proxy1和proxy2,最终proxy2又代理了proxy1,那么执行完后,返回的是proxy2对象。
接下来的关键点是在bean生命周期里的后置处理器了,BeanPostProcessor是对bean的最后一次加强。跟踪代码,spring会执行下面这段代码,AbstractAutoProxyCreator的postProcessAfterInitialization方法,InfrastructureAdvisorAutoProxyCreator和BeanNameAutoProxyCreator都是一种BeanPostProcessor,因此会执行2次,顺序跟执行getEarlyBeanReference方法一致,前者先执行:
/** * Create a proxy with the configured interceptors if the bean is * identified as one to proxy by the subclass. * @see #getAdvicesAndAdvisorsForBean */ public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { if (bean != null) { Object cacheKey = getCacheKey(bean.getClass(), beanName); if (!this.earlyProxyReferences.contains(cacheKey)) { return wrapIfNecessary(bean, beanName, cacheKey); } } return bean; }
这里又会执行2次?为什么呢?因为前面的getEarlyBeanReference方法执行2次后,后面的对象proxy2代理了proxy1。这里传入的bean还是原生对象,第一次执行的时候还是正确的,但第2次执行时(也就是BeanNameAutoProxyCreator)就会出现问题,因为之前earlyProxyReferences里保存的是对proxy1对象的创建状态,而传入的bean还是原生对象,那么显然是没有的,因此又有了对象proxy3,这个proxy3返回后,赋值给了变量'exposedObject ',如下:
// Initialize the bean instance. Object exposedObject = bean; try { populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) { exposedObject = initializeBean(beanName, exposedObject, mbd); } }
接下来是异常抛出的地点了:
if (earlySingletonExposure) { Object earlySingletonReference = getSingleton(beanName, false); if (earlySingletonReference != null) { if (exposedObject == bean) { exposedObject = earlySingletonReference; } else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) { String[] dependentBeans = getDependentBeans(beanName); Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length); for (String dependentBean : dependentBeans) { if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) { actualDependentBeans.add(dependentBean); } } if (!actualDependentBeans.isEmpty()) { throw new BeanCurrentlyInCreationException(beanName, "Bean with name '" + beanName + "' has been injected into other beans [" + StringUtils.collectionToCommaDelimitedString(actualDependentBeans) + "] in its raw version as part of a circular reference, but has eventually been " + "wrapped. This means that said other beans do not use the final version of the " + "bean. This is often the result of over-eager type matching - consider using " + "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example."); } } } }
上面第2行代码的earlySingletonReference=proxy2,exposedObject=proxy3,bean=原始的bean对象,因此结局就有了最上面的异常。
我的解决方法:
解决方法是不用BeanNameAutoProxyCreator,改用<aop:config>。
<bean id="methodProfileAdvice" class="name.zhengwei.demo.spring.aop.MethodProfileAdvice"></bean> <!-- 进行aop配置 --> <aop:config proxy-target-class="false"> <!-- 配置日志切面 --> <aop:aspect id="methodProfileAspect" ref="methodProfileAdvice"> <aop:pointcut id="methodProfilePointcut" expression="execution(* name.zhengwei.demo.spring.service..*.*(..))" /> <!-- 将methodProfileAdvice通知中的方法指定为环绕通知 --> <aop:around method="myAroundAdvice" pointcut-ref="methodProfilePointcut"/> </aop:aspect> </aop:config>
原因:
因为在解析的时候会判断是否已经存在InfrastructureAdvisorAutoProxyCreator,AspectJAwareAdvisorAutoProxyCreator,AnnotationAwareAspectJAutoProxyCreator三者之一,有就合并,否则就注册一个,因此始终就只会有一个代理创建器。
<aop:config>会交给org.springframework.aop.config.AopNamespaceHandler处理
registerBeanDefinitionParser("config", new ConfigBeanDefinitionParser());
ConfigBeanDefinitionParser的parse方法会解析配置:
public BeanDefinition parse(Element element, ParserContext parserContext) { CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), parserContext.extractSource(element)); parserContext.pushContainingComponent(compositeDef); configureAutoProxyCreator(parserContext, element); NodeList childNodes = element.getChildNodes(); for (int i = 0; i < childNodes.getLength(); i++) { Node node = childNodes.item(i); if (node.getNodeType() == Node.ELEMENT_NODE) { String localName = parserContext.getDelegate().getLocalName(node); if (POINTCUT.equals(localName)) { parsePointcut((Element) node, parserContext); } else if (ADVISOR.equals(localName)) { parseAdvisor((Element) node, parserContext); } else if (ASPECT.equals(localName)) { parseAspect((Element) node, parserContext); } } } parserContext.popAndRegisterContainingComponent(); return null; }
看其中的configureAutoProxyCreator方法,会委托给AopNamespaceUtils的registerAspectJAutoProxyCreatorIfNecessary方法处理:
/** * Configures the auto proxy creator needed to support the {@link BeanDefinition BeanDefinitions} * created by the '<code><aop:config/></code>' tag. Will force class proxying if the * '<code>proxy-target-class</code>' attribute is set to '<code>true</code>'. * @see AopNamespaceUtils */ private void configureAutoProxyCreator(ParserContext parserContext, Element element) { AopNamespaceUtils.registerAspectJAutoProxyCreatorIfNecessary(parserContext, element); }
AopNamespaceUtils的registerAspectJAutoProxyCreatorIfNecessary方法:
public static void registerAspectJAutoProxyCreatorIfNecessary( ParserContext parserContext, Element sourceElement) { BeanDefinition beanDefinition = AopConfigUtils.registerAspectJAutoProxyCreatorIfNecessary( parserContext.getRegistry(), parserContext.extractSource(sourceElement)); useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement); registerComponentIfNecessary(beanDefinition, parserContext); }
AopConfigUtils的registerAspectJAutoProxyCreatorIfNecessary方法:
public static BeanDefinition registerAspectJAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) { return registerOrEscalateApcAsRequired(AspectJAwareAdvisorAutoProxyCreator.class, registry, source); }
registerOrEscalateApcAsRequired方法:
private static BeanDefinition registerOrEscalateApcAsRequired(Class cls, BeanDefinitionRegistry registry, Object source) { Assert.notNull(registry, "BeanDefinitionRegistry must not be null"); if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) { BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME); if (!cls.getName().equals(apcDefinition.getBeanClassName())) { int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName()); int requiredPriority = findPriorityForClass(cls); if (currentPriority < requiredPriority) { apcDefinition.setBeanClassName(cls.getName()); } } return null; } RootBeanDefinition beanDefinition = new RootBeanDefinition(cls); beanDefinition.setSource(source); beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE); beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE); registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition); return beanDefinition; }
上面代码,判断是否存在id='org.springframework.aop.config.internalAutoProxyCreator'的bean,否则注册一个,如果有,那么进行合并。
参考:
http://jinnianshilongnian.iteye.com/blog/1901694