spring核心IOC和AOP，終於到aop，看起來真心費力。

demo

<?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:ss="http://www.springframework.org/schema/security"
       xmlns:jee="http://www.springframework.org/schema/jee"
 

       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd
    http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/security http://www.springframework.org/schema/security/spring-security.xsd
    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd"
 

       default-autowire="byName">

    <aop:aspectj-autoproxy />

        <bean id="test" class="qbb.aop.TestBean" />
        <bean class="qbb.aop.AspectJTest" />

</beans>

public class TestBean {

    private  String testStr = "testStr";

    public String getTestStr() {
        return
 
 testStr;
    }

    public void setTestStr(String testStr) {
        this.testStr = testStr;
    }

    public void cout(){
        System.out.println("test");
    }
}

@Aspect
public class AspectJTest {

    @Pointcut("execution(* *.cout(..))")
    public  void test(){
    }

    @Before("test()")
    public void beforeTest(){
        System.out.println("beforeTest");
    }

    @After("test()")
    public void afterTest(){
        System.out.println("afterTest");
    }

    @Around("test()")
    public Object arroundTest(ProceedingJoinPoint p){
        System.out.println("before1");
        Object o = null;
        try {
            o = p.proceed();
        }catch (Throwable e){
            e.printStackTrace();
        }
        System.out.println("after1");
        return o;
    }

}

test

public class AopTest {

    public static void main(String[] args){
        ApplicationContext ctx = new ClassPathXmlApplicationContext("spring-aop.xml");
        TestBean testBean = (TestBean) ctx.getBean("test");
        testBean.cout();
    }

}

aop自定義標籤分析

aop採用自定義標籤解析。

http\://www.springframework.org/schema/aop=org.springframework.aop.config.AopNamespaceHandler

http\://www.springframework.org/schema/aop/spring-aop-2.0.xsd=org/springframework/aop/config/spring-aop-2.0.xsd
http\://www.springframework.org/schema/aop/spring-aop-2.5.xsd=org/springframework/aop/config/spring-aop-2.5.xsd
http\://www.springframework.org/schema/aop/spring-aop-3.0.xsd=org/springframework/aop/config/spring-aop-3.0.xsd
http\://www.springframework.org/schema/aop/spring-aop-3.1.xsd=org/springframework/aop/config/spring-aop-3.1.xsd
http\://www.springframework.org/schema/aop/spring-aop.xsd=org/springframework/aop/config/spring-aop-3.1.xsd

標籤的處理AopNamespaceHandler:

//AopNamespaceHandler
public class AopNamespaceHandler extends NamespaceHandlerSupport {

    public void init() {
        // In 2.0 XSD as well as in 2.1 XSD.
        //處理xml中的配置advisor
        registerBeanDefinitionParser("config", new ConfigBeanDefinitionParser());
        //註解的Aspect解析
        registerBeanDefinitionParser("aspectj-autoproxy", new AspectJAutoProxyBeanDefinitionParser());
        //下面2個沒用過
        registerBeanDefinitionDecorator("scoped-proxy", new ScopedProxyBeanDefinitionDecorator());

        // Only in 2.0 XSD: moved to context namespace as of 2.1
        registerBeanDefinitionParser("spring-configured", new SpringConfiguredBeanDefinitionParser());
    }

}

之前自定義標籤看過，遇到自定義自定義標籤，首先uri找到namespacehandler，呼叫init方法註冊標籤的解析beanDefinitionparser，然後呼叫beanDefinitionParser的parser解析返回beanDefinition註冊到beanfactory裡面去。
aop這裡註冊了不同的標籤解析handler，主要看下aspectj-autoproxy的handlerAspectJAutoProxyBeanDefinitionParser。

//AspectJAutoProxyBeanDefinitionParser
public BeanDefinition parse(Element element, ParserContext parserContext) {
    //解析aspectj-autoproxy標籤
    AopNamespaceUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(parserContext, element);
    //解析子標籤
    extendBeanDefinition(element, parserContext);
    return null;
}

//AopNamespaceUtils
public static void registerAspectJAnnotationAutoProxyCreatorIfNecessary(
        ParserContext parserContext, Element sourceElement) {

    BeanDefinition beanDefinition = AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(
            parserContext.getRegistry(), parserContext.extractSource(sourceElement));
    //設定proxy-target-class和expose-proxy2個屬性
    useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement);
    //註冊元件，然後fire
    registerComponentIfNecessary(beanDefinition, parserContext);
}

//AopConfigUtils
public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
    //註冊或升級解析bean:AnnotationAwareAspectJAutoProxyCreator
    return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
}

private static BeanDefinition registerOrEscalateApcAsRequired(Class cls, BeanDefinitionRegistry registry, Object source) {
    Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
    //如果已經有，就比較優先順序，改變beanClassName
    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);
    //註冊beanDefinition，最終aop通過這個bean來實現
    registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);
    return beanDefinition;
}

這裡只是註冊了一個解析bean，沒有真正實現aop的功能，功能實現通過註冊的bean：AnnotationAwareAspectJAutoProxyCreator在getbean的時候通過BeanPostProcessor實現。

AnnotationAwareAspectJAutoProxyCreator

AnnotationAwareAspectJAutoProxyCreator是實現了BeanPostProcessor（初始化前，初始化後處理器）和InstantiationAwareBeanPostProcessor（例項化前，例項化後處理器）2個介面來實現aop功能。

大致看下方法實現：

//AbstractAutoProxyCreator
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
    Object cacheKey = getCacheKey(beanClass, beanName); //快取取現

    if (!this.targetSourcedBeans.contains(cacheKey)) {
        //是否處理過或者不需要
        if (this.advisedBeans.contains(cacheKey) || this.nonAdvisedBeans.contains(cacheKey)) {
            return null;
        }
        //是否基礎類或者跳過
        //isInfrastructureClass判斷是否Advisor、Advice、AopInfrastructureBean
        //shouldSkip子類實現，如果aspect切面類和要代理的類名相同，那就skip
        if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
            this.nonAdvisedBeans.add(cacheKey);
            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.
    // 自定義的TargetSource，如果你需要在執行時，動態切換代理例項或者新生成一個，就可以試試這個玩意
    TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
    if (targetSource != null) {
        this.targetSourcedBeans.add(beanName);
        //獲取bean適配的Advice
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
        //建立代理
        Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
        this.proxyTypes.put(cacheKey, proxy.getClass());
        return proxy;
    }

    return null;
}

public boolean postProcessAfterInstantiation(Object bean, String beanName) {
    return true;
}

public Object postProcessBeforeInitialization(Object bean, String beanName) {
    return bean;
}

public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    if (bean != null) {
        Object cacheKey = getCacheKey(bean.getClass(), beanName);
        if (!this.earlyProxyReferences.contains(cacheKey)) {
            return wrapIfNecessary(bean, beanName, cacheKey);
        }
    }
    return bean;
}

//是否需要aop解析
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
    if (this.targetSourcedBeans.contains(beanName)) {
        return bean;
    }
    if (this.nonAdvisedBeans.contains(cacheKey)) {
        return bean;
    }
    if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
        this.nonAdvisedBeans.add(cacheKey);
        return bean;
    }

    // Create proxy if we have advice.
    Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
    if (specificInterceptors != DO_NOT_PROXY) {
        this.advisedBeans.add(cacheKey);
        Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
        this.proxyTypes.put(cacheKey, proxy.getClass());
        return proxy;
    }

    this.nonAdvisedBeans.add(cacheKey);
    return bean;
}

最重要的2個方法

//獲取適合的advise
getAdvicesAndAdvisorsForBean

//建立代理類
createProxy

getAdvicesAndAdvisorsForBean獲取適合的advise

//AbstractAdvisorAutoProxyCreator
protected Object[] getAdvicesAndAdvisorsForBean(Class beanClass, String beanName, TargetSource targetSource) {
    List advisors = findEligibleAdvisors(beanClass, beanName);
    if (advisors.isEmpty()) {
        return DO_NOT_PROXY;
    }
    return advisors.toArray();
}

//獲取匹配的Advisor
protected List<Advisor> findEligibleAdvisors(Class beanClass, String beanName) {
    //獲取所有Advisor
    List<Advisor> candidateAdvisors = findCandidateAdvisors();
    //獲取匹配的
    List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
    extendAdvisors(eligibleAdvisors);
    if (!eligibleAdvisors.isEmpty()) {
        eligibleAdvisors = sortAdvisors(eligibleAdvisors);
    }
    return eligibleAdvisors;
}

邏輯清晰，首先獲取所有的advisor，然後找到匹配當前bean的advisor。

findCandidateAdvisors獲取所有的advisor

// AnnotationAwareAspectJAutoProxyCreator
// 獲取所有的advisor
protected List<Advisor> findCandidateAdvisors() {
    // Add all the Spring advisors found according to superclass rules.
    // 獲取xml裡面配置advisor
    List<Advisor> advisors = super.findCandidateAdvisors();
    // Build Advisors for all AspectJ aspects in the bean factory.
    // 獲取aspect註解的advisor
    advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
    return advisors;
}

findCandidateAdvisors獲取xml裡面配置的advisor分2步：
1. 從beanfactory中獲取beanNameType為Advisor的所有beanNames；
2. 從beanfactory中getBean，建立這些advisor的bean。

buildAspectJAdvisors獲取註解Aspect的advisor

// BeanFactoryAspectJAdvisorsBuilder
// 獲取註解Aspect的advisor
public List<Advisor> buildAspectJAdvisors() {
    List<String> aspectNames = null;

    synchronized (this) {
        aspectNames = this.aspectBeanNames;
        if (aspectNames == null) {
            List<Advisor> advisors = new LinkedList<Advisor>();
            aspectNames = new LinkedList<String>();
            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);
                if (beanType == null) {
                    continue;
                }
                // 過濾型別必須為Aspect型別
                if (this.advisorFactory.isAspect(beanType)) {
                    aspectNames.add(beanName);
                    // AspectMetadata是aspect的元資料
                    AspectMetadata amd = new AspectMetadata(beanType, beanName);
                    // 預設就是SINGLETON
                    if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
                        // factory的實現可以保證AspectMetadata例項化一次
                        MetadataAwareAspectInstanceFactory factory =
                                new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
                        // 獲取註解Aspect的advisor
                        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.EMPTY_LIST;
    }

    //如果已經處理過了，直接從快取取
    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;
}

首先看是否解析過Aspect元資料，沒解析過就重頭開始，解析過就從快取裡面取wrap的factory，獲取advisor。

getAdvisors

//ReflectiveAspectJAdvisorFactory
public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory maaif) {
    // 都是通過Aspect元資料的來解析，解析標記Aspect的類的class
    final Class<?> aspectClass = maaif.getAspectMetadata().getAspectClass();
    // 獲取name
    final String aspectName = maaif.getAspectMetadata().getAspectName();
    // 校驗aspect類的是否有註解Aspect，為Singleton
    validate(aspectClass);

    // We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
    // so that it will only instantiate once.
    // 保證元資料Aspect生成的例項唯一
    final MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
            new LazySingletonAspectInstanceFactoryDecorator(maaif);

    final List<Advisor> advisors = new LinkedList<Advisor>();
    // doWithMethods的時候不但解析本Aspect，如果有Superclass，也會，如果不是superlclass，是介面的話，解析所有介面的
    ReflectionUtils.doWithMethods(aspectClass, new ReflectionUtils.MethodCallback() {
        public void doWith(Method method) throws IllegalArgumentException {
            // Exclude pointcuts
            // 不解析pointCut註解，這個註解是在匹配canApplay的getClassFilter過濾時處理
            if (AnnotationUtils.getAnnotation(method, Pointcut.class) == null) {
                // 解析方法上的advisor
                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.
    // advisor不為空，且配置的是延遲初始化，加入同步例項化advisor
    if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
        Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
        advisors.add(0, instantiationAdvisor);
    }

    // Find introduction fields.
    // declareParents註解
    for (Field field : aspectClass.getDeclaredFields()) {
        Advisor advisor = getDeclareParentsAdvisor(field);
        if (advisor != null) {
            advisors.add(advisor);
        }
    }

    return advisors;
}

看到處理方式是對Aspect類的非pointcut方法進行解析：

//ReflectiveAspectJAdvisorFactory
public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aif,
        int declarationOrderInAspect, String aspectName) {

    validate(aif.getAspectMetadata().getAspectClass());

    // 方法註解上的註解表示式
    // 註解:Before, Around, After, AfterReturning, AfterThrowing, Pointcut
    AspectJExpressionPointcut ajexp =
            getPointcut(candidateAdviceMethod, aif.getAspectMetadata().getAspectClass());
    if (ajexp == null) {
        return null;
    }
    // 封裝advisor，構造會區分不同註解的Advice
    return new InstantiationModelAwarePointcutAdvisorImpl(
            this, ajexp, aif, candidateAdviceMethod, declarationOrderInAspect, aspectName);
}

//獲取註解表示式
private AspectJExpressionPointcut getPointcut(Method candidateAdviceMethod, Class<?> candidateAspectClass) {
    // 註解:Before, Around, After, AfterReturning, AfterThrowing, Pointcut
    AspectJAnnotation<?> aspectJAnnotation =
            AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
    if (aspectJAnnotation == null) {
        return null;
    }
    // 解析註解表示式，只是單純註解上表達式，不會關聯pointcut
    AspectJExpressionPointcut ajexp =
            new AspectJExpressionPointcut(candidateAspectClass, new String[0], new Class[0]);
    ajexp.setExpression(aspectJAnnotation.getPointcutExpression());
    return ajexp;
}

注意在解析method上註解表示式後會根據統一封裝成InstantiationModelAwarePointcutAdvisorImpl，該類的構造會區分不同的Advice：

// ReflectiveAspectJAdvisorFactory
public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut ajexp,
        MetadataAwareAspectInstanceFactory aif, int declarationOrderInAspect, String aspectName) {

    Class<?> candidateAspectClass = aif.getAspectMetadata().getAspectClass();
    validate(candidateAspectClass);

    AspectJAnnotation<?> aspectJAnnotation =
            AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
    if (aspectJAnnotation == null) {
        return null;
    }

    ...
    AbstractAspectJAdvice springAdvice;

    switch (aspectJAnnotation.getAnnotationType()) {
        case AtBefore:
            springAdvice = new AspectJMethodBeforeAdvice(candidateAdviceMethod, ajexp, aif);
            break;
        case AtAfter:
            springAdvice = new AspectJAfterAdvice(candidateAdviceMethod, ajexp, aif);
            break;
        case AtAfterReturning:
            springAdvice = new AspectJAfterReturningAdvice(candidateAdviceMethod, ajexp, aif);
            AfterReturning afterReturningAnnotation = (AfterReturning) aspectJAnnotation.getAnnotation();
            if (StringUtils.hasText(afterReturningAnnotation.returning())) {
                springAdvice.setReturningName(afterReturningAnnotation.returning());
            }
            break;
        case AtAfterThrowing:
            springAdvice = new AspectJAfterThrowingAdvice(candidateAdviceMethod, ajexp, aif);
            AfterThrowing afterThrowingAnnotation = (AfterThrowing) aspectJAnnotation.getAnnotation();
            if (StringUtils.hasText(afterThrowingAnnotation.throwing())) {
                springAdvice.setThrowingName(afterThrowingAnnotation.throwing());
            }
            break;
        case AtAround:
            springAdvice = new AspectJAroundAdvice(candidateAdviceMethod, ajexp, aif);
            break;
        case AtPointcut:
            if (logger.isDebugEnabled()) {
                logger.debug("Processing pointcut '" + candidateAdviceMethod.getName() + "'");
            }
            return null;
        default:
            throw new UnsupportedOperationException(
                    "Unsupported advice type on method " + candidateAdviceMethod);
    }

    // Now to configure the advice...
    springAdvice.setAspectName(aspectName);
    springAdvice.setDeclarationOrder(declarationOrderInAspect);
    String[] argNames = this.parameterNameDiscoverer.getParameterNames(candidateAdviceMethod);
    if (argNames != null) {
        springAdvice.setArgumentNamesFromStringArray(argNames);
    }
    springAdvice.calculateArgumentBindings();
    return springAdvice;
}

不同的註解對應不同的封裝。雖然都是Advice的封裝，但是AspectJMethodBeforeAdvice、AspectJAfterReturningAdvice不是通過MethodInterceptor實現，其他幾個是通過MethodInterceptor的invoke實現，
不過最後的最後所有Advice都會統一封裝成MethodInterceptor的實現類。

記得一點：所有的Advice最後都會封裝成MethodInterceptor實現類。

findAdvisorsThatCanApply匹配當前bean的advisor

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

    ProxyCreationContext.setCurrentProxiedBeanName(beanName);
    try {
        //  在找到所有advisor後，再查詢匹配當前要代理bean的advisor
        return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
    }
    finally {
        ProxyCreationContext.setCurrentProxiedBeanName(null);
    }
}

// AopUtils
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) {
        // 引介增強
        if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
            eligibleAdvisors.add(candidate);
        }
    }
    boolean hasIntroductions = !eligibleAdvisors.isEmpty();
    for (Advisor candidate : candidateAdvisors) {
        // 過濾處理過的
        if (candidate instanceof IntroductionAdvisor) {
            // already processed
            continue;
        }
        // 匹配
        if (canApply(candidate, clazz, hasIntroductions)) {
            eligibleAdvisors.add(candidate);
        }
    }
    return eligibleAdvisors;
}

// 查詢是否匹配
public static boolean canApply(Advisor advisor, Class<?> targetClass, boolean hasIntroductions) {
    // 引介增強
    if (advisor instanceof IntroductionAdvisor) {
        return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
    }
    else if (advisor instanceof PointcutAdvisor) {
        // 一般的advisor
        PointcutAdvisor pca = (PointcutAdvisor) advisor;
        return canApply(pca.getPointcut(), targetClass, hasIntroductions);
    }
    else {
        // It doesn't have a pointcut so we assume it applies.
        return true;
    }
}

裡面有個特殊的引介IntroductionAdvisor，當已經有一個類，你想在執行時動態的為這個類增加一些執行方法（相當於又實現了其他介面方法），就可以嘗試引介advisor。

canApply

// AopUtils
public static boolean canApply(Pointcut pc, Class<?> targetClass, boolean hasIntroductions) {
    // 在getClassFilter呼叫中buildPointcutExpression方法完成PointCut註解的解析，這裡是匹配類級別
    if (!pc.getClassFilter().matches(targetClass)) {
        return false;
    }

    MethodMatcher methodMatcher = pc.getMethodMatcher();
    IntroductionAwareMethodMatcher introductionAwareMethodMatcher = null;
    if (methodMatcher instanceof IntroductionAwareMethodMatcher) {
        introductionAwareMethodMatcher = (IntroductionAwareMethodMatcher) methodMatcher;
    }

    // 獲取目標代理類的所有實現介面
    Set<Class> classes = new HashSet<Class>(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
    classes.add(targetClass);
    for (Class<?> clazz : classes) {
        Method[] methods = clazz.getMethods();
        for (Method method : methods) {
            // 匹配方法級
            if ((introductionAwareMethodMatcher != null &&
                    introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions)) ||
                    methodMatcher.matches(method, targetClass)) {
                return true;
            }
        }
    }

    return false;
}

這裡首先完成pointcut註解的解析，然後匹配類級別，然後對目標類的每個實現方法，完成方法級別的匹配，裡面太複雜，看了幾遍，還是有些細節沒把握好。

createProxy建立代理類

在找到目標類的所有匹配的advisor後，開始建立代理物件。

// AbstractAutoProxyCreator
protected Object createProxy(
        Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {

    ProxyFactory proxyFactory = new ProxyFactory();
    // Copy our properties (proxyTargetClass etc) inherited from ProxyConfig.
    // 複製一些屬性 other.optimize; proxyTargetClass\optimize\exposeProxy\frozen\opaque
    proxyFactory.copyFrom(this);

    // 給定的bean是否使用targetClass作為target還是介面代理
    // 基本是proxyTargetClass和bean配置的preserveTargetClass2個屬性值
    if (!shouldProxyTargetClass(beanClass, beanName)) {
        // Must allow for introductions; can't just set interfaces to
        // the target's interfaces only.
        // 加入所有實現介面
        Class<?>[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, this.proxyClassLoader);
        for (Class<?> targetInterface : targetInterfaces) {
            proxyFactory.addInterface(targetInterface);
        }
    }

    // 對之前匹配的advisor處理下
    Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
    for (Advisor advisor : advisors) {
        proxyFactory.addAdvisor(advisor);
    }

    proxyFactory.setTargetSource(targetSource);
    customizeProxyFactory(proxyFactory); //子類實現，可以更改一些設定

    proxyFactory.setFrozen(this.freezeProxy);
    if (advisorsPreFiltered()) {
        proxyFactory.setPreFiltered(true);
    }

    // 獲取代理
    return proxyFactory.getProxy(this.proxyClassLoader);
}

buildAdvisors

// AbstractAutoProxyCreator
protected Advisor[] buildAdvisors(String beanName, Object[] specificInterceptors) {
    // Handle prototypes correctly...
    // 解析this.interceptorNames中的Advisor，通過beanName獲取bean，加到advisor裡面，說實話，暫時沒看到有呼叫設定的地方，可以pass先
    // 可以配置一些通用的
    Advisor[] commonInterceptors = resolveInterceptorNames();

    List<Object> allInterceptors = new ArrayList<Object>();
    if (specificInterceptors != null) {
        // 當前匹配的
        allInterceptors.addAll(Arrays.asList(specificInterceptors));
        if (commonInterceptors != null) {
            if (this.applyCommonInterceptorsFirst) {
                allInterceptors.addAll(0, Arrays.asList(commonInterceptors));
            }
            else {
                allInterceptors.addAll(Arrays.asList(commonInterceptors));
            }
        }
    }
    if (logger.isDebugEnabled()) {
        int nrOfCommonInterceptors = (commonInterceptors != null ? commonInterceptors.length : 0);
        int nrOfSpecificInterceptors = (specificInterceptors != null ? specificInterceptors.length : 0);
        logger.debug("Creating implicit proxy for bean '" + beanName + "' with " + nrOfCommonInterceptors +
                " common interceptors and " + nrOfSpecificInterceptors + " specific interceptors");
    }

    Advisor[] advisors = new Advisor[allInterceptors.size()];
    for (int i = 0; i < allInterceptors.size(); i++) {
        // wrap操作：統一封裝成advisor
        advisors[i] = this.advisorAdapterRegistry.wrap(allInterceptors.get(i));
    }
    return advisors;
}

// DefaultAdvisorAdapterRegistry
// 將攔截器，advisor、advice什麼的都統一封裝成advisor先
public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException {
    if (adviceObject instanceof Advisor) {
        return (Advisor) adviceObject;
    }
    if (!(adviceObject instanceof Advice)) {
        throw new UnknownAdviceTypeException(adviceObject);
    }
    Advice advice = (Advice) adviceObject;
    if (advice instanceof MethodInterceptor) {
        // So well-known it doesn't even need an adapter.
        return new DefaultPointcutAdvisor(advice);
    }
    for (AdvisorAdapter adapter : this.adapters) {
        // Check that it is supported.
        if (adapter.supportsAdvice(advice)) {
            return new DefaultPointcutAdvisor(advice);
        }
    }
    throw new UnknownAdviceTypeException(advice);
}

可以認為buildAdvisors，這一步是將所有攔截器、advisor、Advice什麼的都統一封裝成Advisor，方便後面處理。

getProxy建立代理物件

// ProxyFactory
public Object getProxy(ClassLoader classLoader) {
    // 建立代理，生成代理物件
    return createAopProxy().getProxy(classLoader);
}

createAopProxy建立代理

// ProxyFactory
protected final synchronized AopProxy createAopProxy() {
    if (!this.active) {
        activate();
    }
    return getAopProxyFactory().createAopProxy(this);
}

// DefaultAopProxyFactory
// 決定是jdk代理還是cglib代理
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()) {
            return new JdkDynamicAopProxy(config);
        }
        if (!cglibAvailable) {
            throw new AopConfigException(
                    "Cannot proxy target class because CGLIB2 is not available. " +
                    "Add CGLIB to the class path or specify proxy interfaces.");
        }
        return CglibProxyFactory.createCglibProxy(config);
    }
    else {
        return new JdkDynamicAopProxy(config);
    }
}

這裡主要是決定是jdk代理還是cglib代理。 jdk只能代理介面，所以如果目標類有實現介面的情況，aop配置proxyTargetClass=true，那就cglib，否則jdk代理，沒有實現介面，那隻能cglib代理。

JdkDynamicAopProxy

jdk動態代理通過InvocationHandler的invoke方法。

// JdkDynamicAopProxy
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 {
        // equals\hashCode方法，內部直接呼叫返回
        if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
            // The target does not implement the equals(Object) method itself.
            return equals(args[0]);
        }
        if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
            // The target does not implement the hashCode() method itself.
            return hashCode();
        }
        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;
        // 內部呼叫是否攔截，通過配置exposeProxy控制
        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 = targetSource.getTarget();
        if (target != null) {
            targetClass = target.getClass();
        }

        // Get the interception chain for this method.
        // 所有攔截器-會將之前沒有實現MethodInterceptor的advice全部轉為實現該介面的類
        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.
        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.
            // 攔截器鏈空，直接呼叫
            retVal = AopUtils.invokeJoinpointUsingReflection(target, method, args);
        }
        else {
            // We need to create a method invocation...
            invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
            // Proceed to the joinpoint through the interceptor chain.
            // 攔截器鏈呼叫
            retVal = invocation.proceed();
        }

        // Massage return value if necessary.
        if (retVal != null && retVal == target && method.getReturnType().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.
            retVal = proxy;
        }
        return retVal;
    }
    finally {
        if (target != null && !targetSource.isStatic()) {
            // Must have come from TargetSource.
            targetSource.releaseTarget(target);
        }
        if (setProxyContext) {
            // Restore old proxy.
            AopContext.setCurrentProxy(oldProxy);
        }
    }
}

getInterceptorsAndDynamicInterceptionAdvice

這一步主要是回去方法匹配的攔截器鏈。

// DefaultAdvisorChainFactory
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);
    boolean hasIntroductions = hasMatchingIntroductions(config, targetClass);
    AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
    // 對所有advisor迴圈判斷
    for (Advisor advisor : config.getAdvisors()) {
        if (advisor instanceof PointcutAdvisor) {
            // Add it conditionally.
            PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
            // 類是否匹配
            if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(targetClass)) {
                // 這裡做轉換，沒有實現methodInterceptor的做適配
                MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
                MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
                // 方法是否匹配