代理对象的创建时机位于Bean的初始化之后，调用Bean的后置处理器AnnotationAwareAspectJAutoProxyCreator的postProcessAfterInitialization方法

postProcessAfterInitialization

org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#postProcessAfterInitialization

  1. public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
  2.     if (bean != null) {
  3.         // 先从缓存中获取代理对象
  4.         Object cacheKey = getCacheKey(bean.getClass(), beanName);
  5.         if (this.earlyProxyReferences.remove(cacheKey) != bean) {
  6.             // 按需生成代理对象
  7.             return wrapIfNecessary(bean, beanName, cacheKey);
  8.         }
  9.     }
  10.     return bean;
  11. }

按需生成代理对象，org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator#wrapIfNecessary

  1. protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
  2.     if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
  3.         return bean;
  4.     }
  5.     if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
  6.         return bean;
  7.     }
  8.     if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
  9.         this.advisedBeans.put(cacheKey, Boolean.FALSE);
  10.         return bean;
  11.     }
  13.     // Create proxy if we have advice.
  14.     /**
  15.      * @see AbstractAdvisorAutoProxyCreator#getAdvicesAndAdvisorsForBean(java.lang.Class, java.lang.String, org.springframework.aop.TargetSource)
  16.      */
  17.     // 获取与当前Bean匹配的切面
  18.     Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
  19.     if (specificInterceptors != DO_NOT_PROXY) {
  20.         this.advisedBeans.put(cacheKey, Boolean.TRUE);
  21.         // 创建代理
  22.         Object proxy = createProxy(
  23.                 bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
  24.         this.proxyTypes.put(cacheKey, proxy.getClass());
  25.         return proxy;
  26.     }
  28.     // 缓存
  29.     this.advisedBeans.put(cacheKey, Boolean.FALSE);
  30.     return bean;
  31. }

解析@Aspect注解，生成Advisor

找被切面增强的Advisor

  1. @Override
  2. @Nullable
  3. protected Object[] getAdvicesAndAdvisorsForBean(
  4.         Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
  6.     List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
  7.     if (advisors.isEmpty()) {
  8.         return DO_NOT_PROXY;
  9.     }
  10.     return advisors.toArray();
  11. }

AbstractAdvisorAutoProxyCreator#findEligibleAdvisors

  1. protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
  2.     /**
  3.      * @see AnnotationAwareAspectJAutoProxyCreator#findCandidateAdvisors()
  4.      */
  5.     // 获取容器中所有的切面Advisor
  6.     // 这里返回的切面中的方法已经是有序的了，
  7.     //先按注解顺序（Around.class, Before.class, After.class, AfterReturning.class, AfterThrowing.class），再按方法名称
  8.     List<Advisor> candidateAdvisors = findCandidateAdvisors();
  9.     // 获取所有能够作用于当前Bean上的Advisor
  10.     List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
  11.     /**
  12.      * @see AspectJAwareAdvisorAutoProxyCreator#extendAdvisors(java.util.List)
  13.      */
  14.     // 往集合第一个位置加入了一个DefaultPointcutAdvisor
  15.     extendAdvisors(eligibleAdvisors);
  16.     if (!eligibleAdvisors.isEmpty()) {
  17.         /**
  18.          * @see AspectJAwareAdvisorAutoProxyCreator#sortAdvisors(java.util.List)
  19.          */
  20.         // 这里是对切面进行排序，例如有@Order注解或者实现了Ordered接口
  21.         eligibleAdvisors = sortAdvisors(eligibleAdvisors);
  22.     }
  23.     return eligibleAdvisors;
  24. }

findCandidateAdvisors

  1. protected List<Advisor> findCandidateAdvisors() {
  2.     // Add all the Spring advisors found according to superclass rules.
  3.     // 获取容器中所有的切面Advisor
  4.     List<Advisor> advisors = super.findCandidateAdvisors();
  5.     // Build Advisors for all AspectJ aspects in the bean factory.
  6.     if (this.aspectJAdvisorsBuilder != null) {
  7.         // 这里还需要解析@Aspect注解，生成Advisor
  8.         advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
  9.     }
  10.     return advisors;
  11. }

findAdvisorsThatCanApply

org.springframework.aop.support.AopUtils#findAdvisorsThatCanApply

  1. public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
  2.     if (candidateAdvisors.isEmpty()) {
  3.         return candidateAdvisors;
  4.     }
  5.     List<Advisor> eligibleAdvisors = new ArrayList<>();
  6.     // InstantiationModelAwarePointcutAdvisorImpl
  7.     for (Advisor candidate : candidateAdvisors) {
  8.         if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
  9.             // IntroductionAdvisor类型为引入切面，具体类型为DeclareParentsAdvisor
  10.             eligibleAdvisors.add(candidate);
  11.         }
  12.     }
  13.     boolean hasIntroductions = !eligibleAdvisors.isEmpty();
  14.     for (Advisor candidate : candidateAdvisors) {
  15.         if (candidate instanceof IntroductionAdvisor) {
  16.             // already processed
  17.             continue;
  18.         }
  19.         // PointCut中的ClassFilter.match 匹配类
  20.         // PointCut中的MethodMatcher.match 匹配方法
  21.         if (canApply(candidate, clazz, hasIntroductions)) {
  22.             // @Aspect，类型为InstantiationModelAwarePointcutAdvisorImpl
  23.             eligibleAdvisors.add(candidate);
  24.         }
  25.     }
  26.     return eligibleAdvisors;
  27. }

创建代理对象

在为业务逻辑组件创建代理对象的时候，使用的是cglib来创建动态代理的。当然了，如果业务逻辑类有实现接口，那么就使用jdk来创建动态代理。

  1. protected Object createProxy(Class<?> beanClass, @Nullable String beanName,
  2.         @Nullable Object[] specificInterceptors, TargetSource targetSource) {
  4.     if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
  5.         AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
  6.     }
  8.     // 创建代理工厂
  9.     ProxyFactory proxyFactory = new ProxyFactory();
  10.     proxyFactory.copyFrom(this);
  12.     if (!proxyFactory.isProxyTargetClass()) {
  13.         // 进来说明proxyTargetClass=false，指定JDK代理
  14.         if (shouldProxyTargetClass(beanClass, beanName)) {
  15.             // 进来这里说明BD中有个属性preserveTargetClass=true，可以BD中属性设置的优先级最高
  16.             proxyFactory.setProxyTargetClass(true);
  17.         }
  18.         else {
  19.             // 这里会判断bean有没有实现接口，没有就只能使用CGlib
  20.             evaluateProxyInterfaces(beanClass, proxyFactory);
  21.         }
  22.     }
  24.     Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
  25.     proxyFactory.addAdvisors(advisors); // 切面
  26.     proxyFactory.setTargetSource(targetSource); // 目标对象
  27.     customizeProxyFactory(proxyFactory);
  29.     proxyFactory.setFrozen(this.freezeProxy);
  30.     if (advisorsPreFiltered()) {
  31.         proxyFactory.setPreFiltered(true);
  32.     }
  34.     // 使用JDK或者CGlib创建代理对象
  35.     return proxyFactory.getProxy(getProxyClassLoader());
  36. }