@[TOC]
系列文档索引
SpringAOP从入门到源码分析大全（一）熟悉动态代理 SpringAOP从入门到源码分析大全（二）熟悉ProxyFactory SpringAOP从入门到源码分析大全（三）ProxyFactory源码分析 SpringAOP从入门到源码分析大全（四）SpringAOP的源码分析 SpringAOP从入门到源码分析大全（五）手写一个编程式AOP
六、@EnableAspectJAutoProxy源码分析
1、AnnotationAwareAspectJAutoProxyCreator源码
使用@EnableAspectJAutoProxy，会引入一个AspectJAutoProxyRegistrar的Bean，这个Bean会注册AnnotationAwareAspectJAutoProxyCreator为BeanDefinition。
AnnotationAwareAspectJAutoProxyCreator集成了AbstractAutoProxyCreator，AbstractAutoProxyCreator实现了SmartInstantiationAwareBeanPostProcessor，在postProcessAfterInitialization方法中，会进行AOP。
注意！该方法中，如果有循环依赖的话，会对Bean提前AOP，循环依赖不是此处讨论的重点。
java
// org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#postProcessAfterInitialization
@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
if (bean != null) {
Object cacheKey = getCacheKey(bean.getClass(), beanName);
if (this.earlyProxyReferences.remove(cacheKey) != bean) {
return wrapIfNecessary(bean, beanName, cacheKey);
}
}
return bean;
}（1）wrapIfNecessary方法
java
// org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#wrapIfNecessary
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
return bean;
}
// advisedBeans表示已经判断过了的Bean，false表示不需要再进行AOP了（循环依赖会提前AOP）
if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
return bean;
}
// 当前正在创建的Bean不用进行AOP，比如切面Bean
if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
// Create proxy if we have advice.
// 判断当前bean是否存在匹配的advice，如果存在则要生成一个代理对象
// 此处根据类以及类中的方法区匹配到Interceptor（也就是Advice），然后生成代理对象，代理对象在执行的时候，还会根据当前参数进行匹配
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
if (specificInterceptors != DO_NOT_PROXY) {
// advisedBeans记录了某个Bean已经进行AOP了
this.advisedBeans.put(cacheKey, Boolean.TRUE);
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;
}（2）createProxy
这就是我们熟悉的，使用ProxyFactory，进行代理对象的创建了。
java
// org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#createProxy
protected Object createProxy(Class<?> beanClass, @Nullable String beanName,
@Nullable Object[] specificInterceptors, TargetSource targetSource) {
if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
}
ProxyFactory proxyFactory = new ProxyFactory();
proxyFactory.copyFrom(this);
if (proxyFactory.isProxyTargetClass()) {
// Explicit handling of JDK proxy targets and lambdas (for introduction advice scenarios)
if (Proxy.isProxyClass(beanClass) || ClassUtils.isLambdaClass(beanClass)) {
// Must allow for introductions; can't just set interfaces to the proxy's interfaces only.
for (Class<?> ifc : beanClass.getInterfaces()) {
proxyFactory.addInterface(ifc);
}
}
}
else {
// No proxyTargetClass flag enforced, let's apply our default checks...
if (shouldProxyTargetClass(beanClass, beanName)) {
proxyFactory.setProxyTargetClass(true);
}
else {
evaluateProxyInterfaces(beanClass, proxyFactory);
}
}
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
proxyFactory.addAdvisors(advisors);
proxyFactory.setTargetSource(targetSource);
customizeProxyFactory(proxyFactory);
proxyFactory.setFrozen(this.freezeProxy);
if (advisorsPreFiltered()) {
proxyFactory.setPreFiltered(true);
}
// Use original ClassLoader if bean class not locally loaded in overriding class loader
ClassLoader classLoader = getProxyClassLoader();
if (classLoader instanceof SmartClassLoader && classLoader != beanClass.getClassLoader()) {
classLoader = ((SmartClassLoader) classLoader).getOriginalClassLoader();
}
return proxyFactory.getProxy(classLoader);
}2、getAdvicesAndAdvisorsForBean查找所有Advisor
java
// org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#getAdvicesAndAdvisorsForBean
@Override
@Nullable
protected Object[] getAdvicesAndAdvisorsForBean(
Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
if (advisors.isEmpty()) {
return DO_NOT_PROXY;
}
return advisors.toArray();
}
// org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#findEligibleAdvisors
protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
// 找到所有的Advisor
List<Advisor> candidateAdvisors = findCandidateAdvisors();
// 进行筛选
List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
extendAdvisors(eligibleAdvisors);
// 对Advisor进行排序，按Ordered接口、@Order注解进行排序
if (!eligibleAdvisors.isEmpty()) {
eligibleAdvisors = sortAdvisors(eligibleAdvisors);
}
return eligibleAdvisors;
}（1）findCandidateAdvisors查找
又回到了AnnotationAwareAspectJAutoProxyCreator
java
// org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator#findCandidateAdvisors
@Override
protected List<Advisor> findCandidateAdvisors() {
// Add all the Spring advisors found according to superclass rules.
// 先找到所有Advisor类型的Bean对象，是父类的方法
List<Advisor> advisors = super.findCandidateAdvisors();
// Build Advisors for all AspectJ aspects in the bean factory.
// 再从所有切面中解析得到Advisor对象
if (this.aspectJAdvisorsBuilder != null) {
advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
}
return advisors;
}（2）查找AspectJ定义的Advisor
java
// org.springframework.aop.aspectj.annotation.BeanFactoryAspectJAdvisorsBuilder#buildAspectJAdvisors
public List<Advisor> buildAspectJAdvisors() {
List<String> aspectNames = this.aspectBeanNames;
if (aspectNames == null) {
synchronized (this) {
aspectNames = this.aspectBeanNames;
if (aspectNames == null) {
List<Advisor> advisors = new ArrayList<>();
aspectNames = new ArrayList<>();
// 把所有的Bean拿出来遍历，判断某个bean的类型是否是Aspect
String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
this.beanFactory, Object.class, true, false);
for (String beanName : beanNames) {
if (!isEligibleBean(beanName)) {
continue;
}
// We must be careful not to instantiate beans eagerly as in this case they
// would be cached by the Spring container but would not have been weaved.
Class<?> beanType = this.beanFactory.getType(beanName, false);
if (beanType == null) {
continue;
}
// (hasAspectAnnotation(clazz) && !compiledByAjc(clazz)); 是否有@Aspect
if (this.advisorFactory.isAspect(beanType)) {
aspectNames.add(beanName);
// 切面的注解信息
AspectMetadata amd = new AspectMetadata(beanType, beanName);
// 如果@Aspect不是perthis、pertarget，那么一个切面只会生成一个对象（单例）
// 并且会将该切面中所对应的Advisor对象进行缓存
if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
MetadataAwareAspectInstanceFactory factory =
new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
// 利用BeanFactoryAspectInstanceFactory来解析Aspect
List<Advisor> classAdvisors = this.advisorFactory.getAdvisors(factory);
if (this.beanFactory.isSingleton(beanName)) {
// 缓存切面所对应的所有Advisor对象
this.advisorsCache.put(beanName, classAdvisors);
}
else {
this.aspectFactoryCache.put(beanName, factory);
}
advisors.addAll(classAdvisors);
}
else {
// Per target or per this.
if (this.beanFactory.isSingleton(beanName)) {
throw new IllegalArgumentException("Bean with name '" + beanName +
"' is a singleton, but aspect instantiation model is not singleton");
}
MetadataAwareAspectInstanceFactory factory =
new PrototypeAspectInstanceFactory(this.beanFactory, beanName);
this.aspectFactoryCache.put(beanName, factory);
advisors.addAll(this.advisorFactory.getAdvisors(factory));
}
}
}
this.aspectBeanNames = aspectNames;
return advisors;
}
}
}
if (aspectNames.isEmpty()) {
return Collections.emptyList();
}
List<Advisor> advisors = new ArrayList<>();
for (String aspectName : aspectNames) {
List<Advisor> cachedAdvisors = this.advisorsCache.get(aspectName);
if (cachedAdvisors != null) {
advisors.addAll(cachedAdvisors);
}
else {
MetadataAwareAspectInstanceFactory factory = this.aspectFactoryCache.get(aspectName);
advisors.addAll(this.advisorFactory.getAdvisors(factory));
}
}
return advisors;
}（3）getAdvisors解析切面Bean
java
// org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory#getAdvisors
@Override
public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) {
Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
String aspectName = aspectInstanceFactory.getAspectMetadata().getAspectName();
validate(aspectClass);
// We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
// so that it will only instantiate once.
// 保证切面Bean对象只会实例化一次
// 一定要注意，这里是直接new出来一个LazySingletonAspectInstanceFactoryDecorator
// 也就是OrderService这个Bean在执行生命周期过程中，会需要判断要不要进行AOP，就会找到切面
// 发现切面如果是pertarget或perthis，那么就会进入到这个方法，就会new LazySingletonAspectInstanceFactoryDecorator
MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
new LazySingletonAspectInstanceFactoryDecorator(aspectInstanceFactory);
List<Advisor> advisors = new ArrayList<>();
// 获取切面类中没有加@Pointcut的方法，并进行排序，进行遍历生成Advisor
for (Method method : getAdvisorMethods(aspectClass)) {
// Prior to Spring Framework 5.2.7, advisors.size() was supplied as the declarationOrderInAspect
// to getAdvisor(...) to represent the "current position" in the declared methods list.
// However, since Java 7 the "current position" is not valid since the JDK no longer
// returns declared methods in the order in which they are declared in the source code.
// Thus, we now hard code the declarationOrderInAspect to 0 for all advice methods
// discovered via reflection in order to support reliable advice ordering across JVM launches.
// Specifically, a value of 0 aligns with the default value used in
// AspectJPrecedenceComparator.getAspectDeclarationOrder(Advisor).
Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, 0, aspectName);
if (advisor != null) {
advisors.add(advisor);
}
}
// If it's a per target aspect, emit the dummy instantiating aspect.
if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
advisors.add(0, instantiationAdvisor);
}
// Find introduction fields.
for (Field field : aspectClass.getDeclaredFields()) {
Advisor advisor = getDeclareParentsAdvisor(field);
if (advisor != null) {
advisors.add(advisor);
}
}
return advisors;
}（4）getAdvisor：根据某个方法生成Advisor
java
// org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory#getAdvisor
@Override
@Nullable
public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
int declarationOrderInAspect, String aspectName) {
validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());
// 拿到当前方法所对应的Pointcut对象，但是注意：如果当前方法上这么写@After("pointcut()")
AspectJExpressionPointcut expressionPointcut = getPointcut(
candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
if (expressionPointcut == null) {
return null;
}
// expressionPointcut 是Pointcut
// candidateAdviceMethod承载了advice
return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
}（5）findAdvisorsThatCanApply进行筛选（回到最初）
java
// org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#findAdvisorsThatCanApply
protected List<Advisor> findAdvisorsThatCanApply(
List<Advisor> candidateAdvisors, Class<?> beanClass, String beanName) {
ProxyCreationContext.setCurrentProxiedBeanName(beanName);
try {
return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
}
finally {
ProxyCreationContext.setCurrentProxiedBeanName(null);
}
}
// org.springframework.aop.support.AopUtils#findAdvisorsThatCanApply
public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
if (candidateAdvisors.isEmpty()) {
return candidateAdvisors;
}
List<Advisor> 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 processed
continue;
}
// canApply就是调用Pointcut的match方法进行匹配，先根据类再根据方法
if (canApply(candidate, clazz, hasIntroductions)) {
eligibleAdvisors.add(candidate);
}
}
return eligibleAdvisors;
}
// org.springframework.aop.support.AopUtils#canApply(org.springframework.aop.Pointcut, java.lang.Class<?>, boolean)
public static boolean canApply(Pointcut pc, Class<?> targetClass, boolean hasIntroductions) {
Assert.notNull(pc, "Pointcut must not be null");
if (!pc.getClassFilter().matches(targetClass)) { // 匹配类
return false;
}
MethodMatcher methodMatcher = pc.getMethodMatcher();
if (methodMatcher == MethodMatcher.TRUE) {
// No need to iterate the methods if we're matching any method anyway...
return true;
}
IntroductionAwareMethodMatcher introductionAwareMethodMatcher = null;
if (methodMatcher instanceof IntroductionAwareMethodMatcher) {
introductionAwareMethodMatcher = (IntroductionAwareMethodMatcher) methodMatcher;
}
Set<Class<?>> classes = new LinkedHashSet<>();
if (!Proxy.isProxyClass(targetClass)) {
classes.add(ClassUtils.getUserClass(targetClass));
}
classes.addAll(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
// 至少有一个方法与方法匹配器匹配
for (Class<?> clazz : classes) {
Method[] methods = ReflectionUtils.getAllDeclaredMethods(clazz);
for (Method method : methods) {
if (introductionAwareMethodMatcher != null ?
introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions) :
methodMatcher.matches(method, targetClass)) {
return true;
}
}
}
return false;
}（6）InstantiationModelAwarePointcutAdvisorImpl的getAdvice方法
java
// org.springframework.aop.aspectj.annotation.InstantiationModelAwarePointcutAdvisorImpl#getAdvice
@Override
public synchronized Advice getAdvice() {
if (this.instantiatedAdvice == null) {
// 根据方法生成Advice
this.instantiatedAdvice = instantiateAdvice(this.declaredPointcut);
}
return this.instantiatedAdvice;
}
private Advice instantiateAdvice(AspectJExpressionPointcut pointcut) {
Advice advice = this.aspectJAdvisorFactory.getAdvice(this.aspectJAdviceMethod, pointcut,
this.aspectInstanceFactory, this.declarationOrder, this.aspectName);
return (advice != null ? advice : EMPTY_ADVICE);
}
java
/// org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory#getAdvice
@Override
@Nullable
public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut expressionPointcut,
MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {
Class<?> candidateAspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
validate(candidateAspectClass);
// 拿到方法上的注解信息
AspectJAnnotation<?> aspectJAnnotation =
AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
if (aspectJAnnotation == null) {
return null;
}
// If we get here, we know we have an AspectJ method.
// Check that it's an AspectJ-annotated class
if (!isAspect(candidateAspectClass)) {
throw new AopConfigException("Advice must be declared inside an aspect type: " +
"Offending method '" + candidateAdviceMethod + "' in class [" +
candidateAspectClass.getName() + "]");
}
if (logger.isDebugEnabled()) {
logger.debug("Found AspectJ method: " + candidateAdviceMethod);
}
AbstractAspectJAdvice springAdvice;
// 挨个判断，进行挨个对应
switch (aspectJAnnotation.getAnnotationType()) {
case AtPointcut:
if (logger.isDebugEnabled()) {
logger.debug("Processing pointcut '" + candidateAdviceMethod.getName() + "'");
}
return null;
case AtAround:
springAdvice = new AspectJAroundAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
case AtBefore:
springAdvice = new AspectJMethodBeforeAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
case AtAfter:
springAdvice = new AspectJAfterAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
case AtAfterReturning:
springAdvice = new AspectJAfterReturningAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterReturning afterReturningAnnotation = (AfterReturning) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterReturningAnnotation.returning())) {
springAdvice.setReturningName(afterReturningAnnotation.returning());
}
break;
case AtAfterThrowing:
springAdvice = new AspectJAfterThrowingAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterThrowing afterThrowingAnnotation = (AfterThrowing) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterThrowingAnnotation.throwing())) {
springAdvice.setThrowingName(afterThrowingAnnotation.throwing());
}
break;
default:
throw new UnsupportedOperationException(
"Unsupported advice type on method: " + candidateAdviceMethod);
}
// Now to configure the advice...
springAdvice.setAspectName(aspectName);
springAdvice.setDeclarationOrder(declarationOrder);
String[] argNames = this.parameterNameDiscoverer.getParameterNames(candidateAdviceMethod);
if (argNames != null) {
springAdvice.setArgumentNamesFromStringArray(argNames);
}
springAdvice.calculateArgumentBindings();
return springAdvice;
}
所以，每个注解对应了一个MethodInterceptor
@Before对应的是AspectJMethodBeforeAdvice，在进行动态代理时会把AspectJMethodBeforeAdvice转成MethodBeforeAdviceInterceptor 先执行advice对应的方法 再执行MethodInvocation的proceed()，会执行下一个Interceptor，如果没有下一个Interceptor了，会执行target对应的方法
@After对应的是AspectJAfterAdvice，直接实现了MethodInterceptor 先执行MethodInvocation的proceed()，会执行下一个Interceptor，如果没有下一个Interceptor了，会执行target对应的方法 再执行advice对应的方法
@Around对应的是AspectJAroundAdvice，直接实现了MethodInterceptor 直接执行advice对应的方法，由@Around自己决定要不要继续往后面调用
@AfterThrowing对应的是AspectJAfterThrowingAdvice，直接实现了MethodInterceptor 先执行MethodInvocation的proceed()，会执行下一个Interceptor，如果没有下一个Interceptor了，会执行target对应的方法 如果上面抛了Throwable，那么则会执行advice对应的方法
@AfterReturning对应的是AspectJAfterReturningAdvice，在进行动态代理时会把AspectJAfterReturningAdvice转成AfterReturningAdviceInterceptor 先执行MethodInvocation的proceed()，会执行下一个Interceptor，如果没有下一个Interceptor了，会执行target对应的方法 执行上面的方法后得到最终的方法的返回值 再执行Advice对应的方法
3、总结
（1）AbstractAdvisorAutoProxyCreator
DefaultAdvisorAutoProxyCreator的父类是AbstractAdvisorAutoProxyCreator。
AbstractAdvisorAutoProxyCreator非常强大以及重要，只要Spring容器中存在这个类型的Bean，就相当于开启了AOP，AbstractAdvisorAutoProxyCreator实际上就是一个BeanPostProcessor，所以在创建某个Bean时，就会进入到它对应的生命周期方法中，比如：在某个Bean初始化之后，会调用wrapIfNecessary()方法进行AOP，底层逻辑是，AbstractAdvisorAutoProxyCreator会找到所有的Advisor，然后判断当前这个Bean是否存在某个Advisor与之匹配（根据Pointcut），如果匹配就表示当前这个Bean有对应的切面逻辑，需要进行AOP，需要产生一个代理对象。
（2）@EnableAspectJAutoProxy
这个注解主要就是往Spring容器中添加了一个AnnotationAwareAspectJAutoProxyCreator类型的Bean。 
AspectJAwareAdvisorAutoProxyCreator继承了AbstractAdvisorAutoProxyCreator，重写了findCandidateAdvisors()方法，AbstractAdvisorAutoProxyCreator只能找到所有Advisor类型的Bean对象，但是AspectJAwareAdvisorAutoProxyCreator除开可以找到所有Advisor类型的Bean对象，还能把@Aspect注解所标注的Bean中的@Before等注解及方法进行解析，并生成对应的Advisor对象。
所以，我们可以理解@EnableAspectJAutoProxy，其实就是像Spring容器中添加了一个AbstractAdvisorAutoProxyCreator类型的Bean，从而开启了AOP，并且还会解析@Before等注解生成Advisor。
（3）流程图
