Spring源码学习笔记（四）-Aop获取增强、切点

获取增强共两步，第一步获取所有增强（findCandidateAdvisors（）），第二步寻找适合该Bean的增强（findAdvisorsThatCanApply）。
在上一章中，

//获取增强
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);

AbstractAdvisorAutoProxyCreator.java

//获取增强
protected Object[] getAdvicesAndAdvisorsForBean(Class beanClass, String beanName, TargetSource targetSource) {
        //获取所有可用的增强
        List advisors = findEligibleAdvisors(beanClass, beanName);
        if (advisors.isEmpty()) {
            return DO_NOT_PROXY;
        }
        return advisors.toArray();

    }
    //增强获取
    protected List findEligibleAdvisors(Class beanClass, String beanName) {
        //获取所有增强
        List candidateAdvisors = findCandidateAdvisors();
        //获取适用的增强
        List eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
        extendAdvisors(eligibleAdvisors);
        if (!eligibleAdvisors.isEmpty()) {
            eligibleAdvisors = sortAdvisors(eligibleAdvisors);
        }
        return eligibleAdvisors;
    }

AnnotationAwareAspectAutoProxyCreator.java

@Override
protected List findCandidateAdvisors() {
     // 在这里调用父类方法加载配置文件中的 AOP 声明（XML的支持）
   List advisors = super.findCandidateAdvisors();
   // 增强注册（注解增强）
   advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
   return advisors;
}

BeanFactoryAspectJAdvisorsBuilder.java

public List buildAspectJAdvisors() {
        List<String> aspectNames = null;

        synchronized (this) {
            aspectNames = this.aspectBeanNames;
            if (aspectNames == null) {
                List advisors = new LinkedList();
                aspectNames = new LinkedList<String>();
                //获取所有的Bean
                String[] beanNames =
    BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.beanFactory, Object.class, true, false);
                //遍历所有的bean
                for (String beanName : beanNames) {
                    //不是增强的直接略过
                    if (!isEligibleBean(beanName)) {
                        continue;
                    }
                //获取Bean类型
                    Class beanType = this.beanFactory.getType(beanName);
                    if (beanType == null) {
                        continue;
                    }
                    //判断是否存在Aspect注解
                    if (this.advisorFactory.isAspect(beanType)) {
                        aspectNames.add(beanName);
                    //创建Bean的元数据，增强 切点 类属性等                     AspectMetadata amd = new AspectMetadata(beanType, beanName);
                        if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) {
                            MetadataAwareAspectInstanceFactory factory =
                                    new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
                   //获取增强
                            List classAdvisors = this.advisorFactory.getAdvisors(factory);
                            if (this.beanFactory.isSingleton(beanName)) {
                            //缓存增强
                                this.advisorsCache.put(beanName, classAdvisors);
                            }
                            else {
                            //缓存增强
                                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;
            }
        }
        //没有增强直接返回空
        if (aspectNames.isEmpty()) {
            return Collections.emptyList();
        }
        //在缓存中直接获取
        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;
    }

ReflectiveAspectJAdvisorFactory.java

@Override
//获取增强
    public List getAdvisors(MetadataAwareAspectInstanceFactory maaif) {
    //获取标记类
        final Class aspectClass = maaif.getAspectMetadata().getAspectClass();
        //获取标记名
        final String aspectName = maaif.getAspectMetadata().getAspectName();
    //验证
        validate(aspectClass);

        // We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
        // so that it will only instantiate once.
        final MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
                new LazySingletonAspectInstanceFactoryDecorator(maaif);

        final List advisors = new LinkedList();
        //遍历方法
        for (Method method : getAdvisorMethods(aspectClass)) {
            Advisor advisor = getAdvisor(method, lazySingletonAspectInstanceFactory, advisors.size(), aspectName);
            if (advisor != null) {
                advisors.add(advisor);
            }
        }

        // 如果增强不为空，且设置延迟加载，需要在首位加入同步实例化增强器（SyntheticInstantiationAdvisor）
        if (!advisors.isEmpty() && lazySingletonAspectInstanceFactory.getAspectMetadata().isLazilyInstantiated()) {
            Advisor instantiationAdvisor = new SyntheticInstantiationAdvisor(lazySingletonAspectInstanceFactory);
            advisors.add(0, instantiationAdvisor);
        }

        // 获取 DeclareParents 注解
        for (Field field : aspectClass.getDeclaredFields()) {
            Advisor advisor = getDeclareParentsAdvisor(field);
            if (advisor != null) {
                advisors.add(advisor);
            }
        }

        return advisors;
    }
    //获取切点
    @Override
    public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aif,
            int declarationOrderInAspect, String aspectName) {
//验证
        validate(aif.getAspectMetadata().getAspectClass());
//切点信息获取
        AspectJExpressionPointcut ajexp =
                getPointcut(candidateAdviceMethod, aif.getAspectMetadata().getAspectClass());
        if (ajexp == null) {
            return null;
        }
        //生成切点增强
        return new InstantiationModelAwarePointcutAdvisorImpl(
                this, ajexp, aif, candidateAdviceMethod, declarationOrderInAspect, aspectName);
    }
//获取信息
private AspectJExpressionPointcut getPointcut(Method candidateAdviceMethod, Class candidateAspectClass) {
//获取方法注解
        AspectJAnnotation aspectJAnnotation =
                AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(candidateAdviceMethod);
        if (aspectJAnnotation == null) {
            return null;
        }
        //提取方法注解详细信息，封装
        AspectJExpressionPointcut ajexp =
                new AspectJExpressionPointcut(candidateAspectClass, new String[0], new Class[0]);
        ajexp.setExpression(aspectJAnnotation.getPointcutExpression());
        return ajexp;
    }
@Override
//获取增强
    public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut ajexp,
            MetadataAwareAspectInstanceFactory aif, int declarationOrderInAspect, String aspectName) {
        //获取注解的类 
        Class candidateAspectClass = aif.getAspectMetadata().getAspectClass();
        //验证
        validate(candidateAspectClass);
        //获取方法上的注解
        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;
        //根据不同的注解类封装增强器
        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;
    }

AbstractAdvisorAutoProxyCreator.java

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

   ProxyCreationContext.setCurrentProxiedBeanName(beanName);
   try {
      // 过滤已经得到的 advisors
      return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
   }
   finally {
      ProxyCreationContext.setCurrentProxiedBeanName(null);
   }
}

AopUtils.java

public static List findAdvisorsThatCanApply(List candidateAdvisors, Class clazz) {
   if (candidateAdvisors.isEmpty()) {
      return candidateAdvisors;
   }
   List eligibleAdvisors = new LinkedList();
   // 首先处理引介增强
   for (Advisor candidate : candidateAdvisors) {
      if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
         eligibleAdvisors.add(candidate);
      }
   }
   boolean hasIntroductions = !eligibleAdvisors.isEmpty();
   for (Advisor candidate : candidateAdvisors) {
      // 引介增强已经处理
      if (candidate instanceof IntroductionAdvisor) {
         continue;
      }
      // 对于普通 bean 的处理 canApply匹配方法
      if (canApply(candidate, clazz, hasIntroductions)) {
         eligibleAdvisors.add(candidate);
      }
   }
   return eligibleAdvisors;
}
//匹配
public static boolean canApply(Advisor advisor, Class targetClass, boolean hasIntroductions) {
   if (advisor instanceof IntroductionAdvisor) {
       //正则匹配
      return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
   }
   else if (advisor instanceof PointcutAdvisor) {
      PointcutAdvisor pca = (PointcutAdvisor) advisor;
      return canApply(pca.getPointcut(), targetClass, hasIntroductions);
   }
   else {
      return true;
   }
}