spring源码解析三（ aop）

主要分三块

1、aop增强器的解析

2、代理对象的生成

3、代理对象方法的调用

一、aop增强器的解析

1、首先EnableAspectJAutoProxy从入手

@Configuration
@EnableAspectJAutoProxy(exposeProxy = true, proxyTargetClass = true)
//EnableAspectJAutoProxy表示开启aop，导入aop处理器
//exposeProxy 表示暴露对象，设置为true后，可以通过AopContext.currentProxy()获取到代理对象
//proxyTargetClass  设置为true，表示使用cglib代理
public class MainConfig {

    @Bean
    public Calculate XXX() {
        return new XXX();
    }
}

点击进入EnableAspectJAutoProxy

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(AspectJAutoProxyRegistrar.class)
public @interface EnableAspectJAutoProxy {

    boolean proxyTargetClass() default false;
  
    boolean exposeProxy() default false;

}

import导入了AspectJAutoProxyRegistrar组件，之前说过import导入组件的方式 IOC导入容器的方式，AspectJAutoProxyRegistrar实现了ImportBeanDefinitionRegistrar ，可以注册bean定义

class AspectJAutoProxyRegistrar implements ImportBeanDefinitionRegistrar {

 
    @Override
    public void registerBeanDefinitions(
            AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        //注册aop后置处理器AnnotationAwareAspectJAutoProxyCreator
        AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);
        //获取EnableAspectJAutoProxy配置的属性
        AnnotationAttributes enableAspectJAutoProxy =
                AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);
        if (enableAspectJAutoProxy.getBoolean("proxyTargetClass")) {
            AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
        }
        if (enableAspectJAutoProxy.getBoolean("exposeProxy")) {
            AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);
        }
    }

2、注册 AnnotationAwareAspectJAutoProxyCreator

public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry) {
        return registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry, null);
    }

public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
        return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
    }

private static BeanDefinition registerOrEscalateApcAsRequired(Class<?> cls, BeanDefinitionRegistry registry, Object source) {
        Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
        //判断是否包含该类，包含的话判断已经存在的和当前的优先级，如果当前的优先级高，就用当前的 
        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;
        }
        //注册AnnotationAwareAspectJAutoProxyCreator
        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;
    }

注册了AnnotationAwareAspectJAutoProxyCreator的bean定义

 可以看到AnnotationAwareAspectJAutoProxyCreator实现了BeanPostProcessor和InstantiationAwareBeanPostProcessor ，前面的文章中Spring后置处理器中有介绍InstantiationAwareBeanPostProcessor， 

在geBean源码中，我们可以发现Object bean = resolveBeforeInstantiation(beanName, mbdToUse);，这里有调用InstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation()方法。

3、AnnotationAwareAspectJAutoProxyCreator.postProcessBeforeInstantiation()

public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
        Object cacheKey = this.getCacheKey(beanClass, beanName);
        // 判断TargetSource缓存中是否包含当前bean，如果不包含，则判断当前bean是否是已经被代理的bean，
        // 如果代理过，则不对当前传入的bean进行处理，如果没代理过，则判断当前bean是否为系统bean，或者是
        // 切面逻辑不会包含的bean，如果是，则将当前bean缓存到advisedBeans中，否则继续往下执行。
        // 经过这一步的处理之后，只有在TargetSource中没有进行缓存，并且应该被切面逻辑环绕，但是目前还未
        // 生成代理对象的bean才会通过此方法。
        if (beanName == null || !this.targetSourcedBeans.contains(beanName)) {
            if (this.advisedBeans.containsKey(cacheKey)) {
                return null;
            }
            //若是基础的class ||或者是否应该跳过 shouldSkip直接返回false
            //是不是Advice PointCut Advisor AopInfrastructureBean Aspect满足任意返回ture
            if (this.isInfrastructureClass(beanClass) || this.shouldSkip(beanClass, beanName)) {
                ////把cacheKey 存放在advisedBeans中
                this.advisedBeans.put(cacheKey, Boolean.FALSE);
                return null;
            }
        }
        // 获取封装当前bean的TargetSource对象，如果不存在，则直接退出当前方法，否则从TargetSource
        // 如果没有实现这个接口，正常情况下不会有，暂时也没接触过，不知道这个接口用来干嘛的
        // 获取当前bean对象，并且判断是否需要将切面逻辑应用在当前bean上。
        if (beanName != null) {
            TargetSource targetSource = this.getCustomTargetSource(beanClass, beanName);
            if (targetSource != null) {
                this.targetSourcedBeans.add(beanName);
                // 获取能够应用当前bean的切面逻辑
                Object[] specificInterceptors = this.getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
                // 根据切面逻辑为当前bean生成代理对象
                Object proxy = this.createProxy(beanClass, beanName, specificInterceptors, targetSource);
                this.proxyTypes.put(cacheKey, proxy.getClass());
                return proxy;
            }
        }
        return null;
    }

4、shouldSkip()

protected boolean shouldSkip(Class<?> beanClass, String beanName) {
        // TODO: Consider optimization by caching the list of the aspect names
        //找到候选的增强器
        //主要的逻辑就在这，解析所有的bean定义，获取Advisor放入缓存中去，在真正创建代理的时候可以直接从缓存中获取
    List<Advisor> candidateAdvisors = findCandidateAdvisors(); 

    for (Advisor advisor : candidateAdvisors) {
        //判断是不是AspectJPointcutAdvisor的实例
        if (advisor instanceof AspectJPointcutAdvisor) {
             if (((AbstractAspectJAdvice) advisor.getAdvice()).getAspectName().equals(beanName)) {
                 return true;
             }
        }
    }
    return super.shouldSkip(beanClass, beanName);
}

protected boolean shouldSkip(Class<?> beanClass, String beanName) {
   return false;
}

5、findCandidateAdvisors()

protected List<Advisor> findCandidateAdvisors() {
        // Add all the Spring advisors found according to superclass rules.
        //这里返回的是实现Advisor接口的类，我们熟悉的配置mybatis事务的时候有见过advisor

        List<Advisor> advisors = super.findCandidateAdvisors();
        // Build Advisors for all AspectJ aspects in the bean factory.
        //配置的切面Aspect是在这里创建增强器的
        advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
        return advisors;
    }

public List<Advisor> buildAspectJAdvisors() {
        List<String> aspectNames = this.aspectBeanNames;

        if (aspectNames == null) {
            synchronized (this) {
                aspectNames = this.aspectBeanNames;
                if (aspectNames == null) {
                    List<Advisor> advisors = new LinkedList<Advisor>();
                    aspectNames = new LinkedList<String>();
                    //找到所有被spring管理的类
                    String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
                            this.beanFactory, Object.class, true, false);
                    //遍历
                    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);
                        if (beanType == null) {
                            continue;
                        }
                        //判断是不是Aspect注解的
                        if (this.advisorFactory.isAspect(beanType)) {
                            aspectNames.add(beanName);
                            AspectMetadata amd = new AspectMetadata(beanType, beanName);
                            if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
                                MetadataAwareAspectInstanceFactory factory =
                                        new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
                                //在这里生成advisors
                                List<Advisor> classAdvisors = this.advisorFactory.getAdvisors(factory);
                                if (this.beanFactory.isSingleton(beanName)) {
                                    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();
        }
        //缓存中有增强器，从缓存中获取返回
        List<Advisor> advisors = new LinkedList<Advisor>();
        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;
    }

6、getAdvisors()

public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) {
        //获取切面类
        Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
        //获取切面名称
        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 ArrayList<Advisor>();
        //获取切面类排除@PointCut标志的所有方法
        for (Method method : getAdvisorMethods(aspectClass)) {
            //每一个方法都调用getAdvisor方法来获取增强器
            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.
        for (Field field : aspectClass.getDeclaredFields()) {
            Advisor advisor = getDeclareParentsAdvisor(field);
            if (advisor != null) {
                advisors.add(advisor);
            }
        }

        return advisors;
    }


public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
      int declarationOrderInAspect, String aspectName) {

   validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());
   //获取aspectj的切点表达式
   AspectJExpressionPointcut expressionPointcut = getPointcut(
         candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
   if (expressionPointcut == null) {
      return null;
   }
   //创建advisor实现类
   return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
         this, aspectInstanceFactory, declarationOrderInAspect, aspectName);
}

private AspectJExpressionPointcut getPointcut(Method candidateAdviceMethod, Class<?> candidateAspectClass) {
        //获取切面注解Around.class, Before.class, After.class, AfterReturning.class, AfterThrowing.class
        AspectJAnnotation<?> aspectJAnnotation =
                AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
        if (aspectJAnnotation == null) {
            return null;
        }
        //获取切点表达式对象 
        AspectJExpressionPointcut ajexp =
                new AspectJExpressionPointcut(candidateAspectClass, new String[0], new Class<?>[0]);
        ajexp.setExpression(aspectJAnnotation.getPointcutExpression());
        ajexp.setBeanFactory(this.beanFactory);
        return ajexp;
    }

public InstantiationModelAwarePointcutAdvisorImpl(AspectJExpressionPointcut declaredPointcut,
            Method aspectJAdviceMethod, AspectJAdvisorFactory aspectJAdvisorFactory,
            MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {

        this.declaredPointcut = declaredPointcut;
        this.declaringClass = aspectJAdviceMethod.getDeclaringClass();
        this.methodName = aspectJAdviceMethod.getName();
        this.parameterTypes = aspectJAdviceMethod.getParameterTypes();
        this.aspectJAdviceMethod = aspectJAdviceMethod;
        this.aspectJAdvisorFactory = aspectJAdvisorFactory;
        this.aspectInstanceFactory = aspectInstanceFactory;
        this.declarationOrder = declarationOrder;
        this.aspectName = aspectName;

        if (aspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
            // Static part of the pointcut is a lazy type.
            Pointcut preInstantiationPointcut = Pointcuts.union(
                    aspectInstanceFactory.getAspectMetadata().getPerClausePointcut(), this.declaredPointcut);

            // Make it dynamic: must mutate from pre-instantiation to post-instantiation state.
            // If it's not a dynamic pointcut, it may be optimized out
            // by the Spring AOP infrastructure after the first evaluation.
            this.pointcut = new PerTargetInstantiationModelPointcut(
                    this.declaredPointcut, preInstantiationPointcut, aspectInstanceFactory);
            this.lazy = true;
        }
        else {
            // A singleton aspect.
            this.pointcut = this.declaredPointcut;
            this.lazy = false;
            //实例化切面
            this.instantiatedAdvice = instantiateAdvice(this.declaredPointcut);
        }
    }

private Advice instantiateAdvice(AspectJExpressionPointcut pcut) {
        return this.aspectJAdvisorFactory.getAdvice(this.aspectJAdviceMethod, pcut,
                this.aspectInstanceFactory, this.declarationOrder, this.aspectName);
    }

public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut expressionPointcut,
            MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) {

        Class<?> candidateAspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
        validate(candidateAspectClass);
        //获取切面注解 
        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;

         //判断注解的类型

switch (aspectJAnnotation.getAnnotationType()) {
            //是切点的返回null
            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);
        //获取方法的参数列表
        String[] argNames = this.parameterNameDiscoverer.getParameterNames(candidateAdviceMethod);
        if (argNames != null) {
            //为切面设置参数
            springAdvice.setArgumentNamesFromStringArray(argNames);
        }
        springAdvice.calculateArgumentBindings();

        return springAdvice;
    }

二、代理对象的生成

AnnotationAwareAspectJAutoProxyCreator实现了BeanPostProcessor，所以在bean初始化完成后会调用postProcessAfterInitialization方法

1、postProcessAfterInitialization()

public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if (bean != null) {

            Object cacheKey = this.getCacheKey(bean.getClass(), beanName);
            if (!this.earlyProxyReferences.contains(cacheKey)) {
                return this.wrapIfNecessary(bean, beanName, cacheKey);
            }
        }

        return bean;
    }

2、wrapIfNecessary()

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;
        }
        //判断当前bean是不是基础类型的bean,或者指定类型的bean 不需要代理
        //shoulaSkip在上面也解析过一次，所以这里一般是从缓存中获取
        if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
            this.advisedBeans.put(cacheKey, Boolean.FALSE);
            return bean;
        }

        // Create proxy if we have advice.
        //获取增强器
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
        if (specificInterceptors != DO_NOT_PROXY) {
            this.advisedBeans.put(cacheKey, Boolean.TRUE);
            //创建代理
            Object proxy = createProxy(
                    bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
            this.proxyTypes.put(cacheKey, proxy.getClass());
            return proxy;
        }
        //放入缓存中
        this.advisedBeans.put(cacheKey, Boolean.FALSE);
        return bean;
    }

3.1、getAdvicesAndAdvisorsForBean()

protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) {
        //查找符合条件的增强器
        List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
        if (advisors.isEmpty()) {
            return DO_NOT_PROXY;
        }
        return advisors.toArray();
    }

protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
        //找到候选的增强器,shouldSkip有该方法，从换从中获取
        List<Advisor> candidateAdvisors = findCandidateAdvisors();
        //从候选的中选出能用的增强器
        List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
        extendAdvisors(eligibleAdvisors);
        if (!eligibleAdvisors.isEmpty()) {
            eligibleAdvisors = sortAdvisors(eligibleAdvisors);
        }
        return eligibleAdvisors;
    }

protected List<Advisor> findAdvisorsThatCanApply(
            List<Advisor> candidateAdvisors, Class<?> beanClass, String beanName) {

        ProxyCreationContext.setCurrentProxiedBeanName(beanName);
        try {
            //获取能用的增强器
            return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
        }
        finally {
            ProxyCreationContext.setCurrentProxiedBeanName(null);
        }
    }

public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
        if (candidateAdvisors.isEmpty()) {
            return candidateAdvisors;
        }
        List<Advisor> eligibleAdvisors = new LinkedList<Advisor>();
        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;
            }
            if (canApply(candidate, clazz, hasIntroductions)) {
                eligibleAdvisors.add(candidate);
            }
        }
        return eligibleAdvisors;
    }

//判断是当前的增强器是否能用 通过方法匹配来计算当前是否合适当前类的增强器
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;
            return canApply(pca.getPointcut(), targetClass, hasIntroductions);
        }
        else {
            // It doesn't have a pointcut so we assume it applies.
            return true;
        }
    }

public static boolean canApply(Pointcut pc, Class<?> targetClass, boolean hasIntroductions) {
        Assert.notNull(pc, "Pointcut must not be null");
        if (!pc.getClassFilter().matches(targetClass)) {
            return false;
        }
        //创建一个方法匹配器
        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;
        }
        //获取本身和接口 
        Set<Class<?>> classes = new LinkedHashSet<Class<?>>(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
        classes.add(targetClass);
        for (Class<?> clazz : classes) {
            //获取所有的方法 进行匹配
            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;
    }

3.2 createProxy()

protected Object createProxy(
            Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {
        //获取容器的类型
        if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
            AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
        }

        ProxyFactory proxyFactory = new ProxyFactory();
        proxyFactory.copyFrom(this);
        //判断是否配置了proxyTargetClass
        if (!proxyFactory.isProxyTargetClass()) {
            if (shouldProxyTargetClass(beanClass, beanName)) {
                proxyFactory.setProxyTargetClass(true);
            }
            else {
                //检测 beanClass 是否实现了接口，若未实现，则将 proxyFactory 的成员变量 proxyTargetClass 设为 true
                evaluateProxyInterfaces(beanClass, proxyFactory);
            }
        }
         //获取容器中的方法增强器
        Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
        proxyFactory.addAdvisors(advisors);
        proxyFactory.setTargetSource(targetSource);
        customizeProxyFactory(proxyFactory);

        proxyFactory.setFrozen(this.freezeProxy);
        if (advisorsPreFiltered()) {
            proxyFactory.setPreFiltered(true);
        }
        //创建代理对象
        return proxyFactory.getProxy(getProxyClassLoader());
    }

public Object getProxy(ClassLoader classLoader) {
        return createAopProxy().getProxy(classLoader);
    }

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.");
            }
            //是接口用jdk代理
            if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
                return new JdkDynamicAopProxy(config);
            }
            //cglib代理
            return new ObjenesisCglibAopProxy(config);
        }
        //jdk代理
        else {
            return new JdkDynamicAopProxy(config);
        }
    }

//创建jdk代理
public Object getProxy(ClassLoader classLoader) {
        if (logger.isDebugEnabled()) {
            logger.debug("Creating JDK dynamic proxy: target source is " + this.advised.getTargetSource());
        }
        Class<?>[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true);
        findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
        return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
    }

三、代理对象方法的调用

这里看下jdk动态代理的调用

org.springframework.aop.framework.JdkDynamicAopProxy#invoke

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        MethodInvocation invocation;
        Object oldProxy = null;
        boolean setProxyContext = false;

        TargetSource targetSource = this.advised.targetSource;
        Class<?> targetClass = null;
        Object target = null;

        try {
            //equal()方法
            if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
                // The target does not implement the equals(Object) method itself.
                return equals(args[0]);
            }
            //hashcode()方法
            else if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
                // The target does not implement the hashCode() method itself.
                return hashCode();
            }
            //方法的类是不是DecoratingProxy
            else if (method.getDeclaringClass() == DecoratingProxy.class) {
                // There is only getDecoratedClass() declared -> dispatch to proxy config.
                return AopProxyUtils.ultimateTargetClass(this.advised);
            }
           //有没有实现Advised
            else if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&
                    method.getDeclaringClass().isAssignableFrom(Advised.class)) {
                // Service invocations on ProxyConfig with the proxy config...
                return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);
            }

            Object retVal;
            //是不是有配置exposeProxy,為true的放入threadLocal中，然后就可以通过AopContext.currentProxy()拿到代理对象
            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.
            //获取被代理对象
            target = targetSource.getTarget();
            if (target != null) {
                targetClass = target.getClass();
            }

            // Get the interception chain for this method.
            //把增强器转为方法拦截器链
            List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);

            // Check whether we have any advice. If we don't, we can fallback on direct
            // reflective invocation of the target, and avoid creating a MethodInvocation.
            //若方法拦截器为空，则直接反射调用目标方法
            if (chain.isEmpty()) {
                // 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 = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
            }
            else {
                // We need to create a method invocation...
                //创建方法拦截器调用链
                invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
                // Proceed to the joinpoint through the interceptor chain.
                //执行方法拦截器调用链
                retVal = invocation.proceed();
            }

            // Massage return value if necessary.
            //获取方法返回值
            Class<?> returnType = method.getReturnType();
            if (retVal != null && retVal == target &&
                    returnType != Object.class && returnType.isInstance(proxy) &&
                    !RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
                // Special case: it returned "this" and the return type of the method
                // is type-compatible. Note that we can't help if the target sets
                // a reference to itself in another returned object.
                //如果方法返回值是this，则将代理对象赋值给retVal
                retVal = proxy;
            }
            //如果方法返回值为基础类型并且不是void，但是返回了null，则报错
            else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {
                throw new AopInvocationException(
                        "Null return value from advice does not match primitive return type for: " + method);
            }
            return retVal;
        }
        finally {
            if (target != null && !targetSource.isStatic()) {
                // Must have come from TargetSource.
                targetSource.releaseTarget(target);
            }
            if (setProxyContext) {
                // Restore old proxy.
                AopContext.setCurrentProxy(oldProxy);
            }
        }
    }