注意: 先明白beanPostProcessor的作用,才能夠明白aop的加載時機
在bean實例化完成之前和完成之後分別會自動BeanPostProcessor接口的postProcessBeforeInitialization和postProcessAfterInitialization方法。
advisorCreator,繼承 spring ioc的擴展接口 beanPostProcessor,主要用來掃描獲取 advisor。
beanPostProcessor作用: Spring容器中完成bean實例化、配置以及其他初始化方法前後要添加一些自己邏輯處理。
我們需要定義一個或多個BeanPostProcessor接口實現類,然後註冊到Spring IoC容器中。
advisor:顧問的意思,封裝了spring aop中的切點和通知。 就是我們常用的@Aspect 註解標記得類
advice:通知,也就是aop中增強的方法。
AbstractAutoProxyCreator:Spring 爲Spring AOP 模塊暴露的可擴展抽象類,也是 AOP 中最核心的抽象類。Nepxion Matrix 框架便是基於此類對AOP進行擴展和增強。
BeanNameAutoProxyCreator:根據指定名稱創建代理對象(阿里大名鼎鼎的連接池框架druid也基於此類做了擴展)。通過設置 advisor,可以對指定的 beanName 進行代理。支持模糊匹配。
AbstractAdvisorAutoProxyCreator:功能比較強大,默認掃描所有Advisor的實現類。相對於根據Bean名稱匹配,該類更加靈活。動態的匹配每一個類,判斷是否可以被代理,並尋找合適的增強類,以及生成代理類。
DefaultAdvisorAutoProxyCreator:AbstractAdvisorAutoProxyCreator的默認實現類。可以單獨使用,在框架中使用AOP,儘量不要手動創建此對象。
AspectJAwareAdvisorAutoProxyCreator:Aspectj的實現方式,也是Spring Aop中最常用的實現方式,如果用註解方式,則用其子類AnnotationAwareAspectJAutoProxyCreator。
AnnotationAwareAspectJAutoProxyCreator:目前最常用的AOP使用方式。spring aop 開啓註解方式之後,該類會掃描所有@Aspect()註釋的類,生成對應的advisor。目前SpringBoot框架中默認支持的方式,自動配置。
圖片來自於: https://www.cnblogs.com/yuxiang1/archive/2018/06/19/9199730.html
1: 創建AnnotationAwareAspectJAutoProxyCreator
對象
2: 掃描容器中的切面,創建PointcutAdvisor
對象
3: 生成代理類
PointcutAdvisor
對象的過程:可以看到在AbstractAutoProxyCreator類中的上層接口實現了BeanPostProcessor接口,
對於下面兩個方法, 重寫的第一個方法,其主要目的在於如果用戶使用了自定義的TargetSource對象,則直接使用該對象生成目標對象,而不會使用Spring的默認邏輯生成目標對象,並且這裏會判斷各個切面邏輯是否可以應用到當前bean上,如果可以,則直接應用,也就是說TargetSource爲使用者在Aop中提供了一個自定義生成目標bean邏輯的方式,並且會應用相應的切面邏輯。對於第二個方法,其主要作用在於Spring生成某個bean之後,將相關的切面邏輯應用到該bean上,
瞭解細緻的TargetSource原理請參考:
https://blog.csdn.net/zxfryp909012366/article/details/82881659
1. 以下是bean實例化之後, 初始化之前操作postProcessBeforeInstantiation
在AbstractAutoProxyCreator類中實現BeanPostProcessor中的下面方法中:
@Override
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
Object cacheKey = getCacheKey(beanClass, beanName);
if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
//advisedBeans用於存儲不可代理的bean,如果包含直接返回
if (this.advisedBeans.containsKey(cacheKey)) {
return null;
}
//判斷當前bean是否可以被代理,然後存入advisedBeans
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.
//獲取封裝當前bean的TargetSource對象,如果不存在,則直接退出當前方法,否則從TargetSource
// 中獲取當前bean對象,並且判斷是否需要將切面邏輯應用在當前bean上。
TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
if (targetSource != null) {
if (StringUtils.hasLength(beanName)) {
this.targetSourcedBeans.add(beanName);
}
// 獲取能夠應用當前bean的切面邏輯
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
// 對生成的代理對象進行緩存
this.proxyTypes.put(cacheKey, proxy.getClass());
//如果最終可以獲得代理類,則返回代理類,直接執行實例化後置通知方法
return proxy;
}
return null;
}
================================================================================================
2. 以下是bean初始完成之後創建代理對象過程:postProcessAfterInitialization
在AbstractAutoProxyCreator類中實現BeanPostProcessor中的下面方法中:
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (bean != null) {
//緩存鍵:1.beanName不爲空的話,使用beanName(FactoryBean會在見面加上"&")
//2.如果beanName爲空,使用Class對象作爲緩存的key
Object cacheKey = getCacheKey(bean.getClass(), beanName);
if (!this.earlyProxyReferences.contains(cacheKey)) {
//如果條件符合,則爲bean生成代理對象
return wrapIfNecessary(bean, beanName, cacheKey);
}
}
return bean;
}
wrapIfNecessary:
代碼流程:
1. 如果已經處理過,且該bean沒有被代理過,則直接返回該bean
2.如果該bean是內部基礎設置類Class 或 配置了該bean不需要代理,則直接返回bean(返回前標記該bean已被處理過)
3.獲取所有適合該bean的增強Advisor
如果增強不爲null,則爲該bean創建代理對象,並返回結果
標記該bean已經被處理過
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
//如果已經處理過(targetSourcedBeans存放已經增強過的bean)
if (beanName != null && this.targetSourcedBeans.contains(beanName)) {
return bean;
}
//advisedBeans的key爲cacheKey,value爲boolean類型,表示是否進行過代理
//已經處理過的bean,不需要再次進行處理,節省時間
if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
return bean;
}
//是否是內部基礎設置類Class || 配置了指定bean不需要代理,如果是的話,直接緩存。
if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
// 獲取當前對象所有適用的Advisor.加入當前對象是orderController,那麼找到所有切點是他的對應的@Aspect註解的類
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
//如果獲取的增強不爲null,則爲該bean創建代理(DO_NOT_PROXY=null)
if (specificInterceptors != DO_NOT_PROXY) {
this.advisedBeans.put(cacheKey, Boolean.TRUE);
//創建代理對象時候會用到是否進行JDK代理或者CGLIB代理
Object proxy = createProxy(
bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
this.proxyTypes.put(cacheKey, proxy.getClass());
return proxy;
}
//標記該cacheKey已經被處理過
this.advisedBeans.put(cacheKey, Boolean.FALSE);
return bean;
}
AspectJAwareAdvisorAutoProxyCreator的實現wrapIfNecessary方法中判斷是否爲基礎類的方法:
protected boolean isInfrastructureClass(Class<?> beanClass) {
//如果bean繼承自Advice、Pointcut、Advisor、AopInfrastructureBean
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;
}
從上面代碼可以看出,繼承自Advice、Pointcut、Advisor、AopInfrastructureBean無法被增強
AnnotationAwareAspectJAutoProxyCreator 繼承了AspectJAwareAdvisorAutoProxyCreator 類 調用父類方法時候
在isInfrastructureClass時候,同時加了isAspect方法實現:
public boolean isAspect(Class<?> clazz) {
//如果bean帶有@Aspect註解,或被Ajc(AspectJ編譯器)編譯
return (hasAspectAnnotation(clazz) && !compiledByAjc(clazz));
}
綜上,如果一個bean繼承自Advice、Pointcut、Advisor、AopInfrastructureBean 或者 帶有@Aspect註解,或被Ajc(AspectJ編譯器)編譯都會被認定爲內部基礎設置類
在AnnotationUtils類中的findAnnotation方法中,判斷這個bean上的註解類型是不是@Aspect
以上②邏輯原文: https://blog.csdn.net/finalcola/article/details/82108745
同時AspectJAwareAdvisorAutoProxyCreator的實現wrapIfNecessary方法中判斷是否要進行代理的方法getAdvicesAndAdvisorsForBean同時會調用
findEligibleAdvisors處理兩件事:
protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
//找到Spring中Advisor的實現類(findCandidateAdvisors)
//將所有擁有@Aspect註解的類轉換爲advisors(aspectJAdvisorsBuilder.buildAspectJAdvisors)
List<Advisor> candidateAdvisors = findCandidateAdvisors();
/* findAdvisorsThatCanApply
找到當前對象適合的所有Advisor。整個過程比較簡單:
遍歷所有的advisor。
查看當前advisor的pointCut是否適用於當前對象,如果是,進入候選隊列,否則跳過。*/
List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
//添加一個默認的advisor,執行時用到。
extendAdvisors(eligibleAdvisors);
if (!eligibleAdvisors.isEmpty()) {
eligibleAdvisors = sortAdvisors(eligibleAdvisors);
}
return eligibleAdvisors;
}
findCandidateAdvisors:
protected List<Advisor> findCandidateAdvisors() {
// Add all the Spring advisors found according to superclass rules.
List<Advisor> advisors = super.findCandidateAdvisors();
// Build Advisors for all AspectJ aspects in the bean factory.
advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
return advisors;
}
super.findCandidateAdvisors()
方法最終調用的是BeanFactoryAdvisorRetrievalHelper.findAdvisorBeans()
方法,我們首先看看該方法的實現:
public List<Advisor> findAdvisorBeans() {
String[] advisorNames = null;
synchronized (this) {
advisorNames = this.cachedAdvisorBeanNames;
if (advisorNames == null) {
// 獲取當前BeanFactory中所有實現了Advisor接口的bean的名稱
advisorNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
this.beanFactory, Advisor.class, true, false);
this.cachedAdvisorBeanNames = advisorNames;
}
}
if (advisorNames.length == 0) {
return new LinkedList<>();
}
// 對獲取到的實現Advisor接口的bean的名稱進行遍歷
List<Advisor> advisors = new LinkedList<>();
for (String name : advisorNames) {
// isEligibleBean()是提供的一個hook方法,用於子類對Advisor進行過濾,這裏默認返回值都是true
if (isEligibleBean(name)) {
// 如果當前bean還在創建過程中,則略過,其創建完成之後會爲其判斷是否需要織入切面邏輯
if (this.beanFactory.isCurrentlyInCreation(name)) {
if (logger.isDebugEnabled()) {
logger.debug("Skipping currently created advisor '" + name + "'");
}
} else {
try {
// 將當前bean添加到結果中
advisors.add(this.beanFactory.getBean(name, Advisor.class));
} catch (BeanCreationException ex) {
// 對獲取過程中產生的異常進行封裝
Throwable rootCause = ex.getMostSpecificCause();
if (rootCause instanceof BeanCurrentlyInCreationException) {
BeanCreationException bce = (BeanCreationException) rootCause;
String bceBeanName = bce.getBeanName();
if (bceBeanName != null &&
this.beanFactory.isCurrentlyInCreation(bceBeanName)) {
if (logger.isDebugEnabled()) {
logger.debug("Skipping advisor '" + name +
"' with dependency on currently created bean: "
+ ex.getMessage());
}
continue;
}
}
throw ex;
}
}
}
}
return advisors;
}
然後其中的 buildAspectJAdvisors
方法,會觸發ReflectiveAspectJAdvisorFactory
中的getAdvisors
方法:
@Override
public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) {
//從 aspectMetadata 中獲取 Aspect()標註的類 class對象
Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
//獲取Aspect()標註的類名
String aspectName = aspectInstanceFactory.getAspectMetadata().getAspectName();
validate(aspectClass);
// We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
// so that it will only instantiate once.
MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
new LazySingletonAspectInstanceFactoryDecorator(aspectInstanceFactory);
List<Advisor> advisors = new LinkedList<>();
//遍歷該類所有方法,根據方法判斷是否能獲取到對應 pointCut,如果有,則生成 advisor 對象
for (Method method : getAdvisorMethods(aspectClass)) {
//這裏繼續看下面的解析
Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), 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.
//獲取 @DeclareParents 註解修飾的屬性(並不常用)
for (Field field : aspectClass.getDeclaredFields()) {
Advisor advisor = getDeclareParentsAdvisor(field);
if (advisor != null) {
advisors.add(advisor);
}
}
return advisors;
}
繼續來看getAdvisor
方法:
@Override
@Nullable
public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
int declarationOrderInAspect, String aspectName) {
validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());
//根據候選方法名,來獲取對應的 pointCut
AspectJExpressionPointcut expressionPointcut = getPointcut(
candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
if (expressionPointcut == null) {
return null;
}
//如果能獲取到 pointCut,則將切點表達式 expressionPointcut、當前
對象ReflectiveAspectJAdvisorFactory、 方法名等包裝成 advisor 對象
return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
}
InstantiationModelAwarePointcutAdvisorImpl
的構造方法會觸發構造通知對象:
public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut expressionPointcut,
MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {
//......
//根據註解類型,匹配對應的通知類型
switch (aspectJAnnotation.getAnnotationType()) {
//前置通知
case AtBefore:
springAdvice = new AspectJMethodBeforeAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
//最終通知
case AtAfter:
springAdvice = new AspectJAfterAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
//後置通知
case AtAfterReturning:
springAdvice = new AspectJAfterReturningAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterReturning afterReturningAnnotation = (AfterReturning) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterReturningAnnotation.returning())) {
springAdvice.setReturningName(afterReturningAnnotation.returning());
}
break;
//異常通知
case AtAfterThrowing:
springAdvice = new AspectJAfterThrowingAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
AfterThrowing afterThrowingAnnotation = (AfterThrowing) aspectJAnnotation.getAnnotation();
if (StringUtils.hasText(afterThrowingAnnotation.throwing())) {
springAdvice.setThrowingName(afterThrowingAnnotation.throwing());
}
break;
//環繞通知
case AtAround:
springAdvice = new AspectJAroundAdvice(
candidateAdviceMethod, expressionPointcut, aspectInstanceFactory);
break;
//切面
case AtPointcut:
if (logger.isDebugEnabled()) {
logger.debug("Processing pointcut '" + candidateAdviceMethod.getName() + "'");
}
return null;
default:
throw new UnsupportedOperationException(
"Unsupported advice type on method: " + candidateAdviceMethod);
}
//......
}
可以看到,根據@Aspect
類中方法的註解類型,生成對應的advice
,並通過通知的構造方法,將通知增強方法,切面表達式傳入到通知當中。
到這裏InstantiationModelAwarePointcutAdvisorImpl
對象構造完畢。
原文:https://blog.csdn.net/uftjtt/article/details/80076733
Spring XML關於ProxyFactoryBean使用配置:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd">
<!-- 業務Bean -->
<bean name="conferenceService" class="com.lanhuigu.spring.ConferenceServiceImpl"></bean>
<!--配置Advice-->
<bean name="logAdvice" class="com.lanhuigu.spring.aop.LoggerAdvice"></bean>
<!--配置ProxyFactoryBean-->
<bean name="aopMethod" class="org.springframework.aop.framework.ProxyFactoryBean">
<!-- 指定通知器 -->
<property name="interceptorNames">
<list>
<value>logAdvice</value>
</list>
</property>
<!-- 需要增強的類 -->
<property name="target" ref="conferenceService"/>
</bean>
</beans>
AopProxy代理對象的生成過程:
最後我們回到最初的AbstractAutoProxyCreator中的createProxy方法中
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();
//獲取當前類中的屬性
proxyFactory.copyFrom(this);
//檢查proxyTargeClass設置以及preserveTargetClass屬性
//決定對於給定的bean是否應該使用targetClass而不是他的接口代理
if (!proxyFactory.isProxyTargetClass()) {
if (shouldProxyTargetClass(beanClass, beanName)) {
proxyFactory.setProxyTargetClass(true);
}
else {
//用來添加代理接口
evaluateProxyInterfaces(beanClass, proxyFactory);
}
}
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
//加入增強器
proxyFactory.addAdvisors(advisors);
//設置要代理的類
proxyFactory.setTargetSource(targetSource);
//定製代理
customizeProxyFactory(proxyFactory);
//用來控制代理工廠被設置後是否還允許修改通知,缺省值爲false
proxyFactory.setFrozen(this.freezeProxy);
if (advisorsPreFiltered()) {
proxyFactory.setPreFiltered(true);
}
return proxyFactory.getProxy(getProxyClassLoader());
}
從上面代碼我們看到對於代理類的創建及處理spring是委託給了ProxyFactory處理的,而在此函數中主要是對ProxyFactory的初始化操作,進而對創建代理做準備,這些初始化操作包括以下內容:
(1)獲取當前類中的屬性
(2)添加代理接口
下面是添加代理接口evaluateProxyInterfaces的函數:
protected void evaluateProxyInterfaces(Class<?> beanClass, ProxyFactory proxyFactory) {
Class<?>[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, getProxyClassLoader());
boolean hasReasonableProxyInterface = false;
for (Class<?> ifc : targetInterfaces) {
if (!isConfigurationCallbackInterface(ifc) && !isInternalLanguageInterface(ifc) &&
ifc.getMethods().length > 0) {
hasReasonableProxyInterface = true;
break;
}
}
if (hasReasonableProxyInterface) {
// Must allow for introductions; can't just set interfaces to the target's interfaces only.
for (Class<?> ifc : targetInterfaces) {
proxyFactory.addInterface(ifc);
}
}
else {
proxyFactory.setProxyTargetClass(true);
}
}
(3)封裝Advisor並加入到ProxyFactory中
(4)設置要代理的類
(5)在spring中還爲子類提供了定製的函數customizeProxyFactory,子類可以在此函數中進行對ProxyFactory的進一步封裝
(6)進行獲取代理操作
在createProxy方法最後返回的getProxy方法中可以看到
public Object getProxy(@Nullable ClassLoader classLoader) {
return createAopProxy().getProxy(classLoader);
}
在上面的getProxy方法中createAopProxy方法,其實現是在DefaultAopProxyFactory中,我們進入到方法內:
@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)) {
return new JdkDynamicAopProxy(config);
}
return new ObjenesisCglibAopProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}
配置類AopAutoConfiguration:
1.5x版本:
@Configuration
@EnableAspectJAutoProxy(proxyTargetClass = true)
@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = false)
public static class CglibAutoProxyConfiguration {
}
2.x版本:
@Configuration
@EnableAspectJAutoProxy(proxyTargetClass = true)
@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = true)
public static class CglibAutoProxyConfiguration {
}
可以看到,在SpringBoot2.x中最主要的變化就是proxy-target-class默認爲true,意味着類代理的時候全部走cglib代理方式,只有爲接口代理時才走jdk代理(注意:這裏爲接口代理,不是指代理目標類是否實現了接口)。所以,在使用springboot2.x的版本中,除了代理目標類是接口外,其餘的代理方式全部採用cglib類型。
總結
Springboot通過自動裝配AopAutoConfiguration配置類,默認自動開啓 AOP 功能。通過註冊 AnnotationAwareAspectJAutoProxyCreator類,來掃描創建所有的Advisor,再通過 Advisor在 Spring IOC的擴展接口中來創建代理類。