版权声明：Collected by Bro_Rabbit only for study https://blog.csdn.net/weixin_38240095/article/details/86494804
三、AOP相关
1. 开启基于注解的AOP代理
给配置类标注@EnableAspectJAutoProxy（当然，切面对象与被增强对象添加到容器中），相当于之前配置文件的<aop:aspectj-autoproxy/>
2. @EnableAspectJAutoProxy原理
注：很多形式相似的注解@Enablexxx表示开启xxx功能，深入时应该找出为容器注册的组件、组件工作时机、组件功能
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
//将AspectJAutoProxyRegistrar组件[源码在下一段]导入至容器,自定义给IoC注册代理一个组件:internalAutoProxyCreator=AnnotationAwareAspectJAutoProxyCreator[AOP核心]
@Import(AspectJAutoProxyRegistrar.class)
public @interface EnableAspectJAutoProxy {
/**
* Indicate whether subclass-based (CGLIB) proxies are to be created as opposed
* to standard Java interface-based proxies. The default is {@code false}.
*/
boolean proxyTargetClass() default false;
/**
* Indicate that the proxy should be exposed by the AOP framework as a {@code ThreadLocal}
* for retrieval via the {@link org.springframework.aop.framework.AopContext} class.
* Off by default, i.e. no guarantees that {@code AopContext} access will work.
* @since 4.3.1
*/
boolean exposeProxy() default false;
}
/**
* Registers an {@link org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator
* AnnotationAwareAspectJAutoProxyCreator} against the current {@link BeanDefinitionRegistry}
* as appropriate based on a given @{@link EnableAspectJAutoProxy} annotation.
*
* @author Chris Beams
* @author Juergen Hoeller
* @since 3.1
* @see EnableAspectJAutoProxy
*/
class AspectJAutoProxyRegistrar implements ImportBeanDefinitionRegistrar {
/**
* Register, escalate, and configure the AspectJ auto proxy creator based on the value
* of the @{@link EnableAspectJAutoProxy#proxyTargetClass()} attribute on the importing
* {@code @Configuration} class.
*/
@Override
public void registerBeanDefinitions(
AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);
AnnotationAttributes enableAspectJAutoProxy =
AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);
if (enableAspectJAutoProxy.getBoolean("proxyTargetClass")) {
AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
}
if (enableAspectJAutoProxy.getBoolean("exposeProxy")) {
AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);
}
}
}
/**
* Utility class for handling registration of AOP auto-proxy creators.
*
* <p>Only a single auto-proxy creator can be registered yet multiple concrete
* implementations are available. Therefore this class wraps a simple escalation
* protocol, allowing classes to request a particular auto-proxy creator and know
* that class, {@code or a subclass thereof}, will eventually be resident
* in the application context.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Mark Fisher
* @since 2.5
* @see AopNamespaceUtils
*/
public abstract class AopConfigUtils {
/**
* The bean name of the internally managed auto-proxy creator.
*/
public static final String AUTO_PROXY_CREATOR_BEAN_NAME =
"org.springframework.aop.config.internalAutoProxyCreator";
/**
* Stores the auto proxy creator classes in escalation order.
*/
private static final List<Class<?>> APC_PRIORITY_LIST = new ArrayList<Class<?>>();
/**
* Setup the escalation list.
*/
static {
APC_PRIORITY_LIST.add(InfrastructureAdvisorAutoProxyCreator.class);
APC_PRIORITY_LIST.add(AspectJAwareAdvisorAutoProxyCreator.class);
APC_PRIORITY_LIST.add(AnnotationAwareAspectJAutoProxyCreator.class);
}
public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) {
return registerAutoProxyCreatorIfNecessary(registry, null);
}
public static BeanDefinition registerAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
return registerOrEscalateApcAsRequired(InfrastructureAdvisorAutoProxyCreator.class, registry, source);
}
public static BeanDefinition registerAspectJAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) {
return registerAspectJAutoProxyCreatorIfNecessary(registry, null);
}
public static BeanDefinition registerAspectJAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
return registerOrEscalateApcAsRequired(AspectJAwareAdvisorAutoProxyCreator.class, registry, source);
}
public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) {
return registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry, null);
}
public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
}
public static void forceAutoProxyCreatorToUseClassProxying(BeanDefinitionRegistry registry) {
if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
BeanDefinition definition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
definition.getPropertyValues().add("proxyTargetClass", Boolean.TRUE);
}
}
public static void forceAutoProxyCreatorToExposeProxy(BeanDefinitionRegistry registry) {
if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
BeanDefinition definition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
definition.getPropertyValues().add("exposeProxy", Boolean.TRUE);
}
}
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;
}
private static int findPriorityForClass(Class<?> clazz) {
return APC_PRIORITY_LIST.indexOf(clazz);
}
private static int findPriorityForClass(String className) {
for (int i = 0; i < APC_PRIORITY_LIST.size(); i++) {
Class<?> clazz = APC_PRIORITY_LIST.get(i);
if (clazz.getName().equals(className)) {
return i;
}
}
throw new IllegalArgumentException(
"Class name [" + className + "] is not a known auto-proxy creator class");
}
}
AnnotationAwareAspectJAutoProxyCreator原理分析
AbstractAutoProxyCreator implements SmartInstantionAwareBeanPostProcessor, BeanFactoryAware，根据继承树可知，AnnotationAwareAspectJAutoProxyCreator具备一个后置处理器及自动装配工厂的功能特点
（1）沿着继承树简单分析
- AbstractAutoProxyCreator # setBeanFactory()
- AbstractAutoProxyCreator#具备业务逻辑的后置处理器相关(postProcessBeforeInstantiation / postProcessAfterInitialization) [Breakpoint]
- AbstractAdvisorAutoProxyCreator#setBeanFactory()重写父类逻辑[Breakpoint]，调用自定义initBeanFactory(ConfigurableListableBeanFactory)
- AnnotationAwareAspectJAutoProxyCreator#initBeanFactory()重写父类逻辑[Breakpoint]
（2）断点流程
[1] 创建IoC容器，传入配置类
[2] 注册配置类，刷新容器(核心方法refresh())
[3] registerBeanPostProcessors(BeanFactory) 注册后置处理器拦截Bean的创建
//org.springframework.context.support.PostProcessorRegistrationDelegate
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
//获取IoC容器中已经定义的所有BeanPostProcessor，还未创建其实例
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(beanFactory, priorityOrderedPostProcessors);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(beanFactory, orderedPostProcessors);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : nonOrderedPostProcessorNames) {
//doGetBean()->getSingleton()->getObject()->createBean()
//注册BeanPostProcessor，实际上就是创建BeanPostProcessor对象并保存在容器中
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
sortPostProcessors(beanFactory, internalPostProcessors);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
以创建internalAutoProxyCreator的BeanPostProcessor [AnnotationAwareAspectJAutoProxyCreator]为例
1) 创建Bean实例
2) populateBean，为其属性赋值
3) initializeBean，初始化Bean
<1> invokeAwareMethods：一系列Aware接口的检查，若实现则注入相应的底层组件，AnnotationAwareAspectJAutoProxyCreator的父类逻辑AbstractAdvisorAutoProxyCreator#setBeanFactory()在此被调用,AnnotationAwareAspectJAutoProxyCreator#initBeanFactory()又在setBeanFactory()中被调用
@Override
protected void initBeanFactory(ConfigurableListableBeanFactory beanFactory) {
super.initBeanFactory(beanFactory);
if (this.aspectJAdvisorFactory == null) {
this.aspectJAdvisorFactory = new ReflectiveAspectJAdvisorFactory(beanFactory);
}
this.aspectJAdvisorsBuilder =
new BeanFactoryAspectJAdvisorsBuilderAdapter(beanFactory, this.aspectJAdvisorFactory);
}
<2>applyBeanPostProcessorsBeforeInitialization
<3> invokeInitMethods
<4> applyBeanPostProcessorsAfterInitialization
4) 加入集合，【排序，】注册至BeanFactory
/**
* Register the given BeanPostProcessor beans.
*/
private static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
for (BeanPostProcessor postProcessor : postProcessors) {
beanFactory.addBeanPostProcessor(postProcessor);
}
}
以上是创建并注册AnnotationAwareAspectJAutoProxyCreator(另一种后置处理器InstantiationAwareBeanPostProcessor)的过程，注册完成后，其将作用于所有之后 创建的Bean的前后 （注意：不是初始化前后）
[4] 在[3]完成后执行finishBeanFactoryInitialization(beanFactory)，完成BeanFactory初始化工作，即创建并注册剩下的单实例Bean: beanFactory.preInstantiateSingletons()
遍历获取容器中所有beanDefinitionNames，依次创建对象getBean(beanName) -> doGetBean(…) -> getSingleton(…) [先从缓存中获取当前Bean，若能取到则说明之前已被创建，直接使用，否则新建并置入缓存] -> getObject(…) -> createBean(…) -> resolveBeforeInstantiation(…)[希望后置处理器返回一个代理对象applyBeanPostProcessorBeforeInstantiation/applyBeanPostProcessorAfterInitialization，若能返回则使用，否则再调用doCreateBean]
/**
* Central method of this class: creates a bean instance,
* populates the bean instance, applies post-processors, etc.
* @see #doCreateBean
*/
@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
if (logger.isDebugEnabled()) {
logger.debug("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;
// Make sure bean class is actually resolved at this point, and
// clone the bean definition in case of a dynamically resolved Class
// which cannot be stored in the shared merged bean definition.
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
"BeanPostProcessor before instantiation of bean failed", ex);
}
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
/**
* Apply before-instantiation post-processors, resolving whether there is a
* before-instantiation shortcut for the specified bean.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @return the shortcut-determined bean instance, or {@code null} if none
*/
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
Object bean = null;
if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
// Make sure bean class is actually resolved at this point.
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
Class<?> targetType = determineTargetType(beanName, mbd);
if (targetType != null) {
bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
if (bean != null) {
bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
}
}
}
mbd.beforeInstantiationResolved = (bean != null);
}
return bean;
}
/**
* Apply InstantiationAwareBeanPostProcessors to the specified bean definition
* (by class and name), invoking their {@code postProcessBeforeInstantiation} methods.
* <p>Any returned object will be used as the bean instead of actually instantiating
* the target bean. A {@code null} return value from the post-processor will
* result in the target bean being instantiated.
* @param beanClass the class of the bean to be instantiated
* @param beanName the name of the bean
* @return the bean object to use instead of a default instance of the target bean, or {@code null}
* @see InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation
*/
protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
if (result != null) {
return result;
}
}
}
return null;
}
结论：AnnotationAspectJAutoProxyCreator会在任何Bean创建之前先尝试返回实例（拦截）
AbstractAutoProxyCreator#具备业务逻辑的后置处理器相关（AnnotationAwareAspectJAutoProxyCreator的作用）
/**
* 每一个Bean创建之前调用
*/
@Override
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
Object cacheKey = getCacheKey(beanClass, beanName);
if (beanName == null || !this.targetSourcedBeans.contains(beanName)) {
//判断当前Bean是否存在于advisedBeans(保存所有需要增强的Bean)
if (this.advisedBeans.containsKey(cacheKey)) {
return null;
}
//【判断1】判断当前Bean的类型是否为“基础类型Advice/Pointcut/Advisor/AopInfrastructureBean” 或者 是否为切面（@Aspect）
//【判断2】是否需要跳过
if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return null;
}
}
// Create proxy here if we have a custom TargetSource.
// Suppresses unnecessary default instantiation of the target bean:
// The TargetSource will handle target instances in a custom fashion.
if (beanName != null) {
TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
if (targetSource != null) {
this.targetSourcedBeans.add(beanName);
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
}
return null;
}
/**
* 每一个Bean初始化后调用
* Create a proxy with the configured interceptors if the bean is
* identified as one to proxy by the subclass.
* @see #getAdvicesAndAdvisorsForBean
*/
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (bean != null) {
Object cacheKey = getCacheKey(bean.getClass(), beanName);
if (!this.earlyProxyReferences.contains(cacheKey)) {
//包装方法
return wrapIfNecessary(bean, beanName, cacheKey);
}
}
return bean;
}
/**
* Wrap the given bean if necessary, i.e. if it is eligible for being proxied.
* @param bean the raw bean instance
* @param beanName the name of the bean
* @param cacheKey the cache key for metadata access
* @return a proxy wrapping the bean, or the raw bean instance as-is
*/
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
if (beanName != null && this.targetSourcedBeans.contains(beanName)) {
return bean;
}
if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
return bean;
}
if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
// Create proxy if we have advice.[KEY]
// 获取当前Bean的所有增强器（通知方法）:从候选增强器中找到可以在当前Bean上使用的增强器的排序数组（AopUtils#findAdvisorsThatCanApply查找哪些通知方法需要切入当前Bean的方法）
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
if (specificInterceptors != DO_NOT_PROXY) {
//保存当前Bean在advisedBeans，表示已被处理
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;
}
/**
* Create an AOP proxy for the given bean.
* @param beanClass the class of the bean
* @param beanName the name of the bean
* @param specificInterceptors the set of interceptors that is
* specific to this bean (may be empty, but not null)
* @param targetSource the TargetSource for the proxy,
* already pre-configured to access the bean
* @return the AOP proxy for the bean
* @see #buildAdvisors
*/
protected Object createProxy(
Class<?> beanClass, String beanName, 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()) {
if (shouldProxyTargetClass(beanClass, beanName)) {
proxyFactory.setProxyTargetClass(true);
}
else {
evaluateProxyInterfaces(beanClass, proxyFactory);
}
}
//获取所有的增强器添加至proxyFactory中
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
for (Advisor advisor : advisors) {
proxyFactory.addAdvisor(advisor);
}
proxyFactory.setTargetSource(targetSource);
customizeProxyFactory(proxyFactory);
proxyFactory.setFrozen(this.freezeProxy);
if (advisorsPreFiltered()) {
proxyFactory.setPreFiltered(true);
}
return proxyFactory.getProxy(getProxyClassLoader());
}
/**
* Return whether the given bean class represents an infrastructure class
* that should never be proxied.
* <p>The default implementation considers Advices, Advisors and
* AopInfrastructureBeans as infrastructure classes.
* @param beanClass the class of the bean
* @return whether the bean represents an infrastructure class
* @see org.aopalliance.aop.Advice
* @see org.springframework.aop.Advisor
* @see org.springframework.aop.framework.AopInfrastructureBean
* @see #shouldSkip
*/
protected boolean isInfrastructureClass(Class<?> beanClass) {
boolean retVal = Advice.class.isAssignableFrom(beanClass) ||
Pointcut.class.isAssignableFrom(beanClass) ||
Advisor.class.isAssignableFrom(beanClass) ||
AopInfrastructureBean.class.isAssignableFrom(beanClass);
if (retVal && logger.isTraceEnabled()) {
logger.trace("Did not attempt to auto-proxy infrastructure class [" + beanClass.getName() + "]");
}
return retVal;
}
/**
* 子类AnnotationAwareAspectJAutoProxyCreator重写上面方法【实际调用】
*/
@Override
protected boolean isInfrastructureClass(Class<?> beanClass) {
// Previously we setProxyTargetClass(true) in the constructor, but that has too
// broad an impact. Instead we now override isInfrastructureClass to avoid proxying
// aspects. I'm not entirely happy with that as there is no good reason not
// to advise aspects, except that it causes advice invocation to go through a
// proxy, and if the aspect implements e.g the Ordered interface it will be
// proxied by that interface and fail at runtime as the advice method is not
// defined on the interface. We could potentially relax the restriction about
// not advising aspects in the future.
return (super.isInfrastructureClass(beanClass) || this.aspectJAdvisorFactory.isAspect(beanClass));
}
/**
*子类AnnotationAwareAspectJAutoProxyCreator重写方法【实际调用】
*/
@Override
protected boolean shouldSkip(Class<?> beanClass, String beanName) {
// TODO: Consider optimization by caching the list of the aspect names
// 获取候选的增强器（切面中的通知方法）集合，每一个增强器是InstantionModelAwarePointcutAdvisor
List<Advisor> candidateAdvisors = findCandidateAdvisors();
for (Advisor advisor : candidateAdvisors) {
if (advisor instanceof AspectJPointcutAdvisor) {
if (((AbstractAspectJAdvice) advisor.getAdvice()).getAspectName().equals(beanName)) {
return true;
}
}
}
//Super version returns false
return super.shouldSkip(beanClass, beanName);
}
//org.springframework.aop.framework.DefaultAopProxyFactory
@Override
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
Class<?> targetClass = config.getTargetClass();
if (targetClass == null) {
throw new AopConfigException("TargetSource cannot determine target class: " +
"Either an interface or a target is required for proxy creation.");
}
if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
//原生Jdk基于接口的动态代理
return new JdkDynamicAopProxy(config);
}
//cglib基于类的动态代理
return new ObjenesisCglibAopProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}
3. 代理对象执行目标方法
(1) 容器保存组件的代理对象（增强后的对象），其中保存了一系列详细信息（比如增强器、目标对象…）
(2) CglibAopProxy#DynamicAdvisedInterceptor#intercept()
@Override
public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
Object oldProxy = null;
boolean setProxyContext = false;
Class<?> targetClass = null;
Object target = null;
try {
if (this.advised.exposeProxy) {
// Make invocation available if necessary.
oldProxy = AopContext.setCurrentProxy(proxy);
setProxyContext = true;
}
// May be null. Get as late as possible to minimize the time we
// "own" the target, in case it comes from a pool...
target = getTarget();
if (target != null) {
targetClass = target.getClass();
}
//1. 获取将要执行的目标方法拦截器链 [KEY]
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
Object retVal;
// Check whether we only have one InvokerInterceptor: that is,
// no real advice, but just reflective invocation of the target.
//2. 如果没有拦截器链，直接执行目标方法
if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) {
// We can skip creating a MethodInvocation: just invoke the target directly.
// Note that the final invoker must be an InvokerInterceptor, so we know
// it does nothing but a reflective operation on the target, and no hot
// swapping or fancy proxying.
Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
retVal = methodProxy.invoke(target, argsToUse);
}
else {
// We need to create a method invocation...
//3. 如果由拦截器链，则使用需要执行的目标对象，目标方法，拦截器链等信息初始化一个CglibMethodInvocation，并调用proceed放行
retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();
}
retVal = processReturnType(proxy, target, method, retVal);
return retVal;
}
finally {
if (target != null) {
releaseTarget(target);
}
if (setProxyContext) {
// Restore old proxy.
AopContext.setCurrentProxy(oldProxy);
}
}
}
(3) 拦截器链的获取过程
<1>List<Object> interceptorList 保存所有拦截器(1+n)，1个默认的ExposeInvocationInterceptor和n个自定义的增强器Advisor
<2>遍历所有增强器，将其转换为Interceptor，registry.getInterceptors(advisor)，得到拦截器链
//org.springframework.aop.framework.DefaultAdvisorChainFactory
@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
Advised config, Method method, Class<?> targetClass) {
// This is somewhat tricky... We have to process introductions first,
// but we need to preserve order in the ultimate list.
List<Object> interceptorList = new ArrayList<Object>(config.getAdvisors().length);
Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
boolean hasIntroductions = hasMatchingIntroductions(config, actualClass);
AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
for (Advisor advisor : config.getAdvisors()) {
if (advisor instanceof PointcutAdvisor) {
// Add it conditionally.
PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
if (MethodMatchers.matches(mm, method, actualClass, hasIntroductions)) {
if (mm.isRuntime()) {
// Creating a new object instance in the getInterceptors() method
// isn't a problem as we normally cache created chains.
for (MethodInterceptor interceptor : interceptors) {
interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
}
}
else {
interceptorList.addAll(Arrays.asList(interceptors));
}
}
}
}
else if (advisor instanceof IntroductionAdvisor) {
IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
if (config.isPreFiltered() || ia.getClassFilter().matches(actualClass)) {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
else {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
return interceptorList;
}
//org.springframework.aop.framework.adapter.DefaultAdvisorAdapterRegistry
@Override
public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
List<MethodInterceptor> interceptors = new ArrayList<MethodInterceptor>(3);
Advice advice = advisor.getAdvice();
//如果是MethodInterceptor则直接加入到集合中
if (advice instanceof MethodInterceptor) {
interceptors.add((MethodInterceptor) advice);
}
//如果不是，使用AdvisorAdapter将增强其转为MethodInterceptor（针对切面的通知）
for (AdvisorAdapter adapter : this.adapters) {
if (adapter.supportsAdvice(advice)) {
interceptors.add(adapter.getInterceptor(advisor));
}
}
if (interceptors.isEmpty()) {
throw new UnknownAdviceTypeException(advisor.getAdvice());
}
//返回MethodInterceptor数组
return interceptors.toArray(new MethodInterceptor[interceptors.size()]);
}
(4) 拦截器链触发 proceed
//org.springframework.aop.framework.ReflectiveMethodInvocation
@Override
public Object proceed() throws Throwable {
// We start with an index of -1 and increment early.
// 【情况一】没有拦截器链时，0-1=-1，直接反射调用目标方法
// 【情况二】到了最后一个拦截器
if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
return invokeJoinpoint();
}
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
// Evaluate dynamic method matcher here: static part will already have
// been evaluated and found to match.
InterceptorAndDynamicMethodMatcher dm =
(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
return dm.interceptor.invoke(this);
}
else {
// Dynamic matching failed.
// Skip this interceptor and invoke the next in the chain.
return proceed();
}
}
else {
// It's an interceptor, so we just invoke it: The pointcut will have
// been evaluated statically before this object was constructed.
return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
}
/**
* Invoke the joinpoint using reflection.
* Subclasses can override this to use custom invocation.
* @return the return value of the joinpoint
* @throws Throwable if invoking the joinpoint resulted in an exception
*/
protected Object invokeJoinpoint() throws Throwable {
return AopUtils.invokeJoinpointUsingReflection(this.target, this.method, this.arguments);
}
//org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(MethodInvocation)
/*
* private static final ThreadLocal<MethodInvocation> invocation =
new NamedThreadLocal<MethodInvocation>("Current AOP method invocation");
*/
@Override
public Object invoke(MethodInvocation mi) throws Throwable {
MethodInvocation oldInvocation = invocation.get();
invocation.set(mi);
try {
//以ExposeInvocationInterceptor为例
//所有拦截器都会再调用proceed进行递归，当满足【情况二】后向逐层向上返回，切面方法将在调用proceed的前后进行调用，比如this.advice.before(mi.getMethod(),mi.getArguments(),mi.getThis());
return mi.proceed();
}
finally {
invocation.set(oldInvocation);
}
}
【AOP总结】
- @EnableAspectJAutoProxy 开启AOP功能
- 原理：向容器中注册一个关键组件AnnotationAwareAspectJProxyCreator
- AnnotationAwareAspectJAutoProxyCreator是一个后置处理器
- 容器的创建流程：
(1) registerBeanPostProcessors() 注册后置处理器，创建AnnotationAwareAspectJAutoProxyCreator
(2) finishBeanFactoryInitialization() 初始化剩下的单实例Bean
创建业务组件和切面组件
AnnotationAwareAspectJAutoProxyCreator拦截其余组件的创建
创建完成后，判断组件是否需要增强，若需要则将切面的通知方法包装为增强器Advisor，为业务逻辑组件创建一个代理对象 - 执行目标方法
(1) 代理对象执行目标方法
(2) CglibAopProxy.intercept()
得到目标方法的拦截器链(Advisor->Interceptor)
链式机制，向下递归执行，向上逐层返回