Spring源码解析-aop

spring核心IOC和AOP，终于到aop，看起来真心费力。

demo

<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自定义标签分析

aop采用自定义标签解析。

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

标签的处理AopNamespaceHandler:

//AopNamespaceHandler
public class AopNamespaceHandler extends NamespaceHandlerSupport {
     

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

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

}

之前自定义标签看过，遇到自定义自定义标签，首先uri找到namespacehandler，调用init方法注册标签的解析beanDefinitionparser，然后调用beanDefinitionParser的parser解析返回beanDefinition注册到beanfactory里面去。
aop这里注册了不同的标签解析handler，主要看下aspectj-autoproxy的handlerAspectJAutoProxyBeanDefinitionParser。

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

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

    BeanDefinition beanDefinition = AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(
            parserContext.getRegistry(), parserContext.extractSource(sourceElement));
    //设置proxy-target-class和expose-proxy2个属性
    useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement);
    //注册组件，然后fire
    registerComponentIfNecessary(beanDefinition, parserContext);
}

//AopConfigUtils
public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
    //注册或升级解析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");
    //如果已经有，就比较优先级，改变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);
    //注册beanDefinition，最终aop通过这个bean来实现
    registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);
    return beanDefinition;
}

这里只是注册了一个解析bean，没有真正实现aop的功能，功能实现通过注册的bean：AnnotationAwareAspectJAutoProxyCreator在getbean的时候通过BeanPostProcessor实现。

AnnotationAwareAspectJAutoProxyCreator

AnnotationAwareAspectJAutoProxyCreator是实现了BeanPostProcessor（初始化前，初始化后处理器）和InstantiationAwareBeanPostProcessor（实例化前，实例化后处理器）2个接口来实现aop功能。

大致看下方法实现：

//AbstractAutoProxyCreator
public Object postProcessBeforeInstantiation(Class beanClass, String beanName) throws BeansException {
    Object cacheKey = getCacheKey(beanClass, beanName); //缓存取现

    if (!this.targetSourcedBeans.contains(cacheKey)) {
        //是否处理过或者不需要
        if (this.advisedBeans.contains(cacheKey) || this.nonAdvisedBeans.contains(cacheKey)) {
            return null;
        }
        //是否基础类或者跳过
        //isInfrastructureClass判断是否Advisor、Advice、AopInfrastructureBean
        //shouldSkip子类实现，如果aspect切面类和要代理的类名相同，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.
    // 自定义的TargetSource，如果你需要在运行时，动态切换代理实例或者新生成一个，就可以试试这个玩意
    TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
    if (targetSource != null) {
        this.targetSourcedBeans.add(beanName);
        //获取bean适配的Advice
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
        //创建代理
        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个方法

//获取适合的advise
getAdvicesAndAdvisorsForBean

//创建代理类
createProxy

getAdvicesAndAdvisorsForBean获取适合的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();
}

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

逻辑清晰，首先获取所有的advisor，然后找到匹配当前bean的advisor。

findCandidateAdvisors获取所有的advisor

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

findCandidateAdvisors获取xml里面配置的advisor分2步：
1. 从beanfactory中获取beanNameType为Advisor的所有beanNames；
2. 从beanfactory中getBean，创建这些advisor的bean。

buildAspectJAdvisors获取注解Aspect的advisor

// BeanFactoryAspectJAdvisorsBuilder
// 获取注解Aspect的advisor
public List buildAspectJAdvisors() {
    List aspectNames = null;

    synchronized (this) {
        aspectNames = this.aspectBeanNames;
        if (aspectNames == null) {
            List advisors = new LinkedList();
            aspectNames = new LinkedList();
            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;
                }
                // 过滤类型必须为Aspect类型
                if (this.advisorFactory.isAspect(beanType)) {
                    aspectNames.add(beanName);
                    // AspectMetadata是aspect的元数据
                    AspectMetadata amd = new AspectMetadata(beanType, beanName);
                    // 默认就是SINGLETON
                    if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
                        // factory的实现可以保证AspectMetadata实例化一次
                        MetadataAwareAspectInstanceFactory factory =
                                new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
                        // 获取注解Aspect的advisor
                        List 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;
    }

    //如果已经处理过了，直接从缓存取
    List advisors = new LinkedList();
    for (String aspectName : aspectNames) {
        List 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;
}

首先看是否解析过Aspect元数据，没解析过就重头开始，解析过就从缓存里面取wrap的factory，获取advisor。

getAdvisors

//ReflectiveAspectJAdvisorFactory
public List getAdvisors(MetadataAwareAspectInstanceFactory maaif) {
    // 都是通过Aspect元数据的来解析，解析标记Aspect的类的class
    final Class aspectClass = maaif.getAspectMetadata().getAspectClass();
    // 获取name
    final String aspectName = maaif.getAspectMetadata().getAspectName();
    // 校验aspect类的是否有注解Aspect，为Singleton
    validate(aspectClass);

    // We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
    // so that it will only instantiate once.
    // 保证元数据Aspect生成的实例唯一
    final MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
            new LazySingletonAspectInstanceFactoryDecorator(maaif);

    final List advisors = new LinkedList();
    // doWithMethods的时候不但解析本Aspect，如果有Superclass，也会，如果不是superlclass，是接口的话，解析所有接口的
    ReflectionUtils.doWithMethods(aspectClass, new ReflectionUtils.MethodCallback() {
        public void doWith(Method method) throws IllegalArgumentException {
            // Exclude pointcuts
            // 不解析pointCut注解，这个注解是在匹配canApplay的getClassFilter过滤时处理
            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不为空，且配置的是延迟初始化，加入同步实例化advisor
    if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
        Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
        advisors.add(0, instantiationAdvisor);
    }

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

    return advisors;
}

看到处理方式是对Aspect类的非pointcut方法进行解析：

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

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

    // 方法注解上的注解表达式
    // 注解:Before, Around, After, AfterReturning, AfterThrowing, Pointcut
    AspectJExpressionPointcut ajexp =
            getPointcut(candidateAdviceMethod, aif.getAspectMetadata().getAspectClass());
    if (ajexp == null) {
        return null;
    }
    // 封装advisor，构造会区分不同注解的Advice
    return new InstantiationModelAwarePointcutAdvisorImpl(
            this, ajexp, aif, candidateAdviceMethod, declarationOrderInAspect, aspectName);
}

//获取注解表达式
private AspectJExpressionPointcut getPointcut(Method candidateAdviceMethod, Class candidateAspectClass) {
    // 注解:Before, Around, After, AfterReturning, AfterThrowing, Pointcut
    AspectJAnnotation aspectJAnnotation =
            AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
    if (aspectJAnnotation == null) {
        return null;
    }
    // 解析注解表达式，只是单纯注解上表达式，不会关联pointcut
    AspectJExpressionPointcut ajexp =
            new AspectJExpressionPointcut(candidateAspectClass, new String[0], new Class[0]);
    ajexp.setExpression(aspectJAnnotation.getPointcutExpression());
    return ajexp;
}

注意在解析method上注解表达式后会根据统一封装成InstantiationModelAwarePointcutAdvisorImpl，该类的构造会区分不同的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;
}

不同的注解对应不同的封装。虽然都是Advice的封装，但是AspectJMethodBeforeAdvice、AspectJAfterReturningAdvice不是通过MethodInterceptor实现，其他几个是通过MethodInterceptor的invoke实现，
不过最后的最后所有Advice都会统一封装成MethodInterceptor的实现类。

记得一点：所有的Advice最后都会封装成MethodInterceptor实现类。

findAdvisorsThatCanApply匹配当前bean的advisor

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

    ProxyCreationContext.setCurrentProxiedBeanName(beanName);
    try {
        //  在找到所有advisor后，再查找匹配当前要代理bean的advisor
        return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
    }
    finally {
        ProxyCreationContext.setCurrentProxiedBeanName(null);
    }
}

// AopUtils
public static List findAdvisorsThatCanApply(List candidateAdvisors, Class clazz) {
    if (candidateAdvisors.isEmpty()) {
        return candidateAdvisors;
    }
    List eligibleAdvisors = new LinkedList();
    for (Advisor candidate : candidateAdvisors) {
        // 引介增强
        if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
            eligibleAdvisors.add(candidate);
        }
    }
    boolean hasIntroductions = !eligibleAdvisors.isEmpty();
    for (Advisor candidate : candidateAdvisors) {
        // 过滤处理过的
        if (candidate instanceof IntroductionAdvisor) {
            // already processed
            continue;
        }
        // 匹配
        if (canApply(candidate, clazz, hasIntroductions)) {
            eligibleAdvisors.add(candidate);
        }
    }
    return eligibleAdvisors;
}

// 查找是否匹配
public static boolean canApply(Advisor advisor, Class targetClass, boolean hasIntroductions) {
    // 引介增强
    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;
    }
}

里面有个特殊的引介IntroductionAdvisor，当已经有一个类，你想在运行时动态的为这个类增加一些运行方法（相当于又实现了其他接口方法），就可以尝试引介advisor。

canApply

// AopUtils
public static boolean canApply(Pointcut pc, Class targetClass, boolean hasIntroductions) {
    // 在getClassFilter调用中buildPointcutExpression方法完成PointCut注解的解析，这里是匹配类级别
    if (!pc.getClassFilter().matches(targetClass)) {
        return false;
    }

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

    // 获取目标代理类的所有实现接口
    Set classes = new HashSet(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
    classes.add(targetClass);
    for (Class clazz : classes) {
        Method[] methods = clazz.getMethods();
        for (Method method : methods) {
            // 匹配方法级
            if ((introductionAwareMethodMatcher != null &&
                    introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions)) ||
                    methodMatcher.matches(method, targetClass)) {
                return true;
            }
        }
    }

    return false;
}

这里首先完成pointcut注解的解析，然后匹配类级别，然后对目标类的每个实现方法，完成方法级别的匹配，里面太复杂，看了几遍，还是有些细节没把握好。

createProxy创建代理类

在找到目标类的所有匹配的advisor后，开始创建代理对象。

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

    ProxyFactory proxyFactory = new ProxyFactory();
    // Copy our properties (proxyTargetClass etc) inherited from ProxyConfig.
    // 复制一些属性 other.optimize; proxyTargetClass\optimize\exposeProxy\frozen\opaque
    proxyFactory.copyFrom(this);

    // 给定的bean是否使用targetClass作为target还是接口代理
    // 基本是proxyTargetClass和bean配置的preserveTargetClass2个属性值
    if (!shouldProxyTargetClass(beanClass, beanName)) {
        // Must allow for introductions; can't just set interfaces to
        // the target's interfaces only.
        // 加入所有实现接口
        Class[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, this.proxyClassLoader);
        for (Class targetInterface : targetInterfaces) {
            proxyFactory.addInterface(targetInterface);
        }
    }

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

    proxyFactory.setTargetSource(targetSource);
    customizeProxyFactory(proxyFactory); //子类实现，可以更改一些设置

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

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

buildAdvisors

// AbstractAutoProxyCreator
protected Advisor[] buildAdvisors(String beanName, Object[] specificInterceptors) {
    // Handle prototypes correctly...
    // 解析this.interceptorNames中的Advisor，通过beanName获取bean，加到advisor里面，说实话，暂时没看到有调用设置的地方，可以pass先
    // 可以配置一些通用的
    Advisor[] commonInterceptors = resolveInterceptorNames();

    List