本文将通过阅读AnnotationAwareAspectJAutoProxyCreator后置处理器的源码，分析其解析AOP通知、匹配切入点和创建AOP代理的流程。

入口

AnnotationAwareAspectJAutoProxyCreator是一个BeanPostProcessor实现，他在容器进行initializeBean的时候被调用：

核心的BeanPostProcessor方法实现都在其父类AbstractAutoProxyCreator中实现。

wrapIfNecessary方法

在其父类AbstractAutoProxyCreator的postProcessAfterInitialization方法中。

核心功能：

• 查找AOP Advisor
• 创建AOP代理

protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {// 最开始是一些是否需要AOP的判断，如果不需要或者已经创建代理，则直接返回了// Create proxy if we have advice.// 查找AOP AdvisorObject[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);if (specificInterceptors != DO_NOT_PROXY) {this.advisedBeans.put(cacheKey, Boolean.TRUE);// 创建AOP代理Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));this.proxyTypes.put(cacheKey, proxy.getClass());return proxy;}this.advisedBeans.put(cacheKey, Boolean.FALSE);return bean;
}

getAdvicesAndAdvisorsForBean方法

查找AOP Advisor

protected Object[] getAdvicesAndAdvisorsForBean(Class beanClass, String beanName, @Nullable TargetSource targetSource) {List advisors = findEligibleAdvisors(beanClass, beanName);if (advisors.isEmpty()) {return DO_NOT_PROXY;}return advisors.toArray();
}// Find all eligible Advisors for auto-proxying this class.
protected List findEligibleAdvisors(Class beanClass, String beanName) {// 此处分为两部分：// 1. 查找Spring容器里面注入的Advisor// 2. 解析所有的AspectJ AOP并创建Advisor// 实现逻辑在AnnotationAwareAspectJAutoProxyCreator类中List candidateAdvisors = findCandidateAdvisors();// Search the given candidate Advisors to find all Advisors that can apply to the specified bean.List eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);// Add an ExposeInvocationInterceptor to the beginning of the advice chain.// This additional advice is needed when using AspectJ pointcut expressions and // when using AspectJ-style advice.extendAdvisors(eligibleAdvisors);if (!eligibleAdvisors.isEmpty()) {eligibleAdvisors = sortAdvisors(eligibleAdvisors);}return eligibleAdvisors;
}// AnnotationAwareAspectJAutoProxyCreator.findCandidateAdvisors
protected List findCandidateAdvisors() {// Add all the Spring advisors found according to superclass rules.// 查找Spring容器里面注入的Advisor，代码就不再展开记录List advisors = super.findCandidateAdvisors();// Build Advisors for all AspectJ aspects in the bean factory.// 解析所有的AspectJ AOP并创建Advisorif (this.aspectJAdvisorsBuilder != null) {advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());}return advisors;
}

过滤当前Bean可用Advisor

findAdvisorsThatCanApply方法用于过滤可用Advisor：

protected List findAdvisorsThatCanApply(List candidateAdvisors, Class beanClass, String beanName) {ProxyCreationContext.setCurrentProxiedBeanName(beanName);try {return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);} finally {ProxyCreationContext.setCurrentProxiedBeanName(null);}
}

AopUtils.findAdvisorsThatCanApply方法：

// Determine the sublist of the candidateAdvisors list that is applicable to the given class.
public static List findAdvisorsThatCanApply(List candidateAdvisors, Class clazz) {List eligibleAdvisors = new ArrayList<>();for (Advisor candidate : candidateAdvisors) {if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {eligibleAdvisors.add(candidate);}}boolean hasIntroductions = !eligibleAdvisors.isEmpty();for (Advisor candidate : candidateAdvisors) {if (candidate instanceof IntroductionAdvisor) {// already processedcontinue;}if (canApply(candidate, clazz, hasIntroductions)) {eligibleAdvisors.add(candidate);}}return eligibleAdvisors;
}public static boolean canApply(Advisor advisor, Class targetClass, boolean hasIntroductions) {if (advisor instanceof IntroductionAdvisor) {return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);} else if (advisor instanceof PointcutAdvisor) {PointcutAdvisor pca = (PointcutAdvisor) advisor;// 使用pointcut判断return canApply(pca.getPointcut(), targetClass, hasIntroductions);} else {return true;}
}

排序

在查找Advisor集的过程中，有一步是Advisor集排序：

protected List findEligibleAdvisors(Class beanClass, String beanName) {List candidateAdvisors = findCandidateAdvisors();List eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);extendAdvisors(eligibleAdvisors);if (!eligibleAdvisors.isEmpty()) {// 排序eligibleAdvisors = sortAdvisors(eligibleAdvisors);}return eligibleAdvisors;
}protected List sortAdvisors(List advisors) {List partiallyComparableAdvisors = new ArrayList<>(advisors.size());for (Advisor advisor : advisors) {partiallyComparableAdvisors.add(new PartiallyComparableAdvisorHolder(advisor, DEFAULT_PRECEDENCE_COMPARATOR));}List sorted = PartialOrder.sort(partiallyComparableAdvisors);if (sorted != null) {List result = new ArrayList<>(advisors.size());for (PartiallyComparableAdvisorHolder pcAdvisor : sorted) {result.add(pcAdvisor.getAdvisor());}return result;} else {return super.sortAdvisors(advisors);}
}

核心的排序逻辑都在DEFAULT_PRECEDENCE_COMPARATOR中，他是一个Comparator实现：

public int compare(Advisor o1, Advisor o2) {int advisorPrecedence = this.advisorComparator.compare(o1, o2);// 如果advisorComparator比较结果相同，将使用AspectJ相关的方法排序，此部分不分析if (advisorPrecedence == SAME_PRECEDENCE && declaredInSameAspect(o1, o2)) {advisorPrecedence = comparePrecedenceWithinAspect(o1, o2);}return advisorPrecedence;
}

advisorComparator也是一个Comparator实现，他内部有一些从Ordered实现方法、Order注解获取顺序的逻辑，此处不展开分析，了解即可。

创建AOP代理

// 创建AOP代理
Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));

createProxy入口方法

protected Object createProxy(Class beanClass, String beanName,Object[] specificInterceptors, TargetSource targetSource) {// Expose the given target class for the specified bean, if possible.if (this.beanFactory instanceof ConfigurableListableBeanFactory) {AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);}ProxyFactory proxyFactory = new ProxyFactory();proxyFactory.copyFrom(this);if (!proxyFactory.isProxyTargetClass()) {if (shouldProxyTargetClass(beanClass, beanName)) {proxyFactory.setProxyTargetClass(true);}else {evaluateProxyInterfaces(beanClass, proxyFactory);}}// 构建AOP通知Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);proxyFactory.addAdvisors(advisors);proxyFactory.setTargetSource(targetSource);customizeProxyFactory(proxyFactory);proxyFactory.setFrozen(this.freezeProxy);if (advisorsPreFiltered()) {proxyFactory.setPreFiltered(true);}// 创建代理return proxyFactory.getProxy(getProxyClassLoader());
}// 构建AOP通知
protected Advisor[] buildAdvisors(String beanName, Object[] specificInterceptors) {Advisor[] commonInterceptors = resolveInterceptorNames();List