SpringAop 流程源码阅读

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AOP的核心概念

由来

AOP是切面的意思,面向对象的思想,设计出来的结构都是树状的,最大程度的提升代码的复用率、扩展性、易读性。但是这里有个问题,树状结构大家都是知道是一种关系型结构,擅长处理关系结构,扩展等方面适合业务功能核心代码的开发。但是对于一些重复的、每个功能都需要用到的功能比如,日志、监控、权限、统计、事务等横向的功能(所有功能都需要的),使用面向对象的思想处理起来的结果就是导致代码重复率高、不易扩展、阅读体验比较差,每次都要看非业务代码。这种情况就适合用切面来处理。因为这个过程和织布机,横向织入横线的过程一样,所以这个过程被称为织入。

关键点

切面的核心点,就是切入点,point,我们需要一个切入点 point cut,围绕这个点进行一些增强处理,可能是前,后,或者环绕式的,这些具体的增强就是advice,而切面 aspect 是包含这两个部分的。但是切面生成之后,如果放到合适的地方,就是需要织入 weaving。

spring中的应用

面向对象的设计中,一个类有两部分组成,成员变量,成员方法。成员变量是属性,运行时标识当前对象的状态,成员方法是action,标识这个类可以做哪些事情。所以AOP增强的最小单位就是成员方法,是对方法的增强。但是方法属于类,所以切入点的通过规则表达式(可以理解过正则表达式)来选定类+方法,具体规则看
所以增强的单位肯定也是方法,可以理解为方法增强。最后的织入过程,我们都知道设计模式中的代理模式,这里就是基于代理模式的思想,通过spring的IOC机制生成代理对象,spring通过IOC获取的都是代理对象,所以很方便的就完成了织入过程。
基于以上的概念,spring aop是分开设计了4种接口

spring中的设计

切入点,主要是用来解析表达式,并且进行类、方法的 match操作,PointCut
增强器,主要用来对方法进行增强:Advice
切面,切入点和增强器的组合具体是流程控制: PointCutAdvisor
织入,获取目标对象是否需要进行代理,如果需要则获取需要进行代理的切面(可能有多个),生成代理对象放入到容器中替换目标对象,AutoProxyCreator

类图

Demo

主入口 main

public class InstalmentApiServer 
  public static void main(String[] args) 
    System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
    log.info("starting main");
    ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]
        "classpath:context/applicationContext.xml",
 , false);
    IHello testA = (IHello) context.getBean("testA");
    testA.sayHello();

xml 配置文件

<?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:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd"
    default-lazy-init="false">
  
  <aop:aspectj-autoproxy/>
  <bean id="testA" class="com.xiaomi.mifi.instalment.api.server.TestA" init-method="initMethod"> </bean>
  <bean id="logAspect" class="com.xiaomi.mifi.instalment.api.server.LogAspect" />
  <!--注册annotation-->
  <context:annotation-config/>
</beans>

切面 LogAspect

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class LogAspect 
  @Around("execution(* com..*(..))")
  private Object errorHandlerAround(ProceedingJoinPoint joinPoint) throws Throwable 
    System.out.println("-----------> LogAspect before");
    Object rs =  joinPoint.proceed();
    System.out.println("-----------> LogAspect After");
    return rs;
  

HelloImpl

public class HelloImpl implements  IHello
  @Override
  public void sayHello() 
    System.out.println("hello world");
  

TestA

import org.springframework.beans.factory.InitializingBean;
import javax.annotation.PostConstruct;

public class TestA implements InitializingBean , IHello

  public TestA() 
    System.out.println("---->TestA constructor this is ");
  

  @PostConstruct
  public void init() 
    System.out.println("PostConstruct");
  

  public void initMethod() 
    System.out.println("initMethod");
  

  public void fooA() 
    System.out.println("----> TestA.fooA this is ");
  

  public void foo() 
    System.out.println("----> TestA.foo this is ");
  

  @Override
  public void afterPropertiesSet() throws Exception 
    System.out.println("afterPropertiesSet");
  

  @Override
  public void sayHello() 
    System.out.println("----> TestA sayHello implement ");
  

开启aop配置

这个触发操作是由于配置

// spring 配置文件, 启动spring AOP
<beans  // aop 命令空间
       xmlns:aop="http://www.springframework.org/schema/aop"
      http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd"
    default-lazy-init="false">
   // 开启  aop配置
<aop:aspectj-autoproxy/>

aop地址空间映射

org.springframework.aop.config.AopNamespaceHandler
这个类用来解析xml配置文件中,aop开头的配置
这个aop命令空间(http://www.springframework.org/schema/aop) 是如何映射到这个类是通过配置文件spring.handlers,来完成的,这个文件在
srping-aop-4.3.30.jar包的,META-INF 目录下面的,spring会加载所有这个名称的文件,用来解析xml文件中的命令空间的
文件内容

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

aop属性解析

org.springframework.aop.config.AopNamespaceHandler

@Override
public void init() 
   // In 2.0 XSD as well as in 2.5+ XSDs
   registerBeanDefinitionParser("config", new ConfigBeanDefinitionParser());
   // 属性  aspectj-autoproxy 的解析
   registerBeanDefinitionParser("aspectj-autoproxy", new AspectJAutoProxyBeanDefinitionParser());
   registerBeanDefinitionDecorator("scoped-proxy", new ScopedProxyBeanDefinitionDecorator());

   // Only in 2.0 XSD: moved to context namespace in 2.5+
   registerBeanDefinitionParser("spring-configured", new SpringConfiguredBeanDefinitionParser());

aop解析细节

具体的细节就是使用AnnotationAwareAspectJAutoProxyCreator类,去向
BeanDefinitionRegistry把beanDefinition注册到工厂类中,bean的创建过程是先创建bena的定义,通过bean的定义再生成的对象。
通过下面的方法完成类:AnnotationAwareAspectJAutoProxyCreator的注册,所有aop的增强都是通过这个类来完成的如果是通过@Aspect注解,注解的切面。
该类的优先级别是最高级别的,先执行

return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);

生成代理类

AbstractAutoProxyCreator
是 AnnotationAwareAspectJAutoProxyCreator 的祖先类的,实现对类的增强是流程主入口。
AnnotationAwareAspectJAutoProxyCreator本身只处理和Aspect注解相关的事情,充分体现面向对象
抽象、继承,的特点,体现了高扩展能力。

主流程

org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator
AbstractAutowireCapableBeanFactory.initializeBean
->applyBeanPostProcessorsAfterInitialization
开始执行 .postProcessAfterInitialization

// spring 解决单例循环依赖的时候,会提前注册一个BeanFactory,这里会提前生成代理类
@Override
public Object getEarlyBeanReference(Object bean, String beanName) throws BeansException 
   Object cacheKey = getCacheKey(bean.getClass(), beanName);
   // 写入这个map的原因,是为了保证单例,这里提前生成了代理类(因为循环依赖),
   // A->B->A , 这种情况下,在创建B的时候,会调用这里提前生成A的代理类,
   // 这个时候B里面的对A的引用已经是新的代理类了,但是A本身的还在初始化的过程中还没完成
   // 需要完成A的初始化,但是还不能重新生成新的代理类否则就不是单例了,所以这里记录
   // 在postProcessAfterInitialization的时候,对比引用,如果一样,就不重新生成代理类了
   // 同时这个方法只会被调用一次,因为单例对象生成过成中会加锁,而且进行缓存,保证创建完成之后
   // 只会从缓存里面取。同时最终A初始化完成之后,会把最终返回的引用对象体会为这里生成的代理对象,保证单例
   this.earlyProxyReferences.put(cacheKey, bean);
   // 生成代理类的具体实现
   return wrapIfNecessary(bean, beanName, cacheKey);


// 正常的非循环依赖的对象,都从这里进行AOP的增强
// 这里的循环依赖指的是单例循环依赖(非构造函数依赖)
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException 
   if (bean != null) 
      Object cacheKey = getCacheKey(bean.getClass(), beanName);
      // 1, 如果是循环依赖则remove返回的bean ,和 当前是bean地址一样,这里是false,直接结束
      // 2, 非循环依赖,那这里remove返回的是null,而bean不为空是先决条件,所以这里返回 true,进行类的增强,生成代理类
      if (this.earlyProxyReferences.remove(cacheKey) != bean) 
         // 生成代理类的具体实现
         return wrapIfNecessary(bean, beanName, cacheKey);
      
   
   return bean;


// 生成代理类
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;
   
   if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) 
      this.advisedBeans.put(cacheKey, Boolean.FALSE);
      return bean;
   

   // Create proxy if we have advice.
   //获取需要增强的切面
   Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
   if (specificInterceptors != DO_NOT_PROXY) 
      // 缓存该类,需要 AOP 增强
      this.advisedBeans.put(cacheKey, Boolean.TRUE);
      // 生成代理类对象
      Object proxy = createProxy(
            bean.getClass(), beanName, specificInterceptors
             // 被代理的对象,在代理类最后调用
            , new SingletonTargetSource(bean));
       // 缓存
      this.proxyTypes.put(cacheKey, proxy.getClass());
      return proxy;
   
   // 缓存该类,不需要 AOP 增强
   this.advisedBeans.put(cacheKey, Boolean.FALSE);
   return bean;


// 生成代理类
protected Object createProxy(
      Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) 
   // 设置属性,把原始类名称,设置到 BeanDefiniiton的属性中
   if (this.beanFactory instanceof ConfigurableListableBeanFactory) 
      AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
   

   ProxyFactory proxyFactory = new ProxyFactory();
   proxyFactory.copyFrom(this);
   // 检查类,是需要代理类,还是代理接口,因为有的类没有接口,只能代理类
   // java JDK proxy只能代理接口,如果是代理类需要使用cgLib生成子类才行
   if (!proxyFactory.isProxyTargetClass()) 
       // 检查类属性是否有生命
      if (shouldProxyTargetClass(beanClass, beanName)) 
         proxyFactory.setProxyTargetClass(true);
      
      else 
         // 如果实现的类是内部类,最后也会代理类
         // proxyFactory.setProxyTargetClass(true);
         evaluateProxyInterfaces(beanClass, proxyFactory);
      
   
   // 生成最终的增强器
   Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
   proxyFactory.addAdvisors(advisors);
   proxyFactory.setTargetSource(targetSource);
   customizeProxyFactory(proxyFactory);

   proxyFactory.setFrozen(this.freezeProxy);
   if (advisorsPreFiltered()) 
      proxyFactory.setPreFiltered(true);
   
    // 生成代理对象
   return proxyFactory.getProxy(getProxyClassLoader());


// 检查是否需要代理类
protected void evaluateProxyInterfaces(Class<?> beanClass, ProxyFactory proxyFactory) 
   Class<?>[] targetInterfaces = ClassUtils.getAllInterfacesForClass(beanClass, getProxyClassLoader());
   boolean hasReasonableProxyInterface = false;
   for (Class<?> ifc : targetInterfaces) 
      if (!isConfigurationCallbackInterface(ifc) && !isInternalLanguageInterface(ifc) &&
            ifc.getMethods().length > 0) 
         hasReasonableProxyInterface = true;
         break;
      
   
   // 有需要代理的接口,则添加代理接口,这里有个问题,就是只能代理接口的方法,
  //   非接口方法无法代理,即使符合pointCut的条件
   if (hasReasonableProxyInterface) 
      // Must allow for introductions; can't just set interfaces to the target's interfaces only.
      for (Class<?> ifc : targetInterfaces) 
         proxyFactory.addInterface(ifc);
      
   
   else 
     // 否则只能代理类
      proxyFactory.setProxyTargetClass(true);
   


// 生成最终的advisor 
protected Advisor[] buildAdvisors(String beanName, Object[] specificInterceptors) 
   // Handle prototypes correctly...
   // 通过配置文件配置的,目前都是通过注解,所以这里一般都是空的
   Advisor[] commonInterceptors = resolveInterceptorNames();

   List<Object> allInterceptors = new ArrayList<Object>();
   if (specificInterceptors != null) 
      allInterceptors.addAll(Arrays.asList(specificInterceptors));
      if (commonInterceptors.length > 0) 
         if (this.applyCommonInterceptorsFirst) 
            allInterceptors.addAll(0, Arrays.asList(commonInterceptors));
         
         else 
            allInterceptors.addAll(Arrays.asList(commonInterceptors));
         
      
   
   Advisor[] advisors = new Advisor[allInterceptors.size()];
   for (int i = 0; i < allInterceptors.size(); i++) 
      // wrap 是进行一次适配的过程,因为要兼容老的切面,所以进行一次兼容处理
      advisors[i] = this.advisorAdapterRegistry.wrap(allInterceptors.get(i));
   
   return advisors;

获取该对象需要增强的切面

org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator
是 org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator
的子类,提供和切面相关的逻辑

@Override
protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) 
   List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
   if (advisors.isEmpty()) 
      return DO_NOT_PROXY;
   
   return advisors.toArray();



protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) 
   // 获取所有的切面, 注意是逻辑见AnnotationAwareAspectJAutoProxyCreator
   List<Advisor> candidateAdvisors = findCandidateAdvisors();
   // 取出符合该对象的切面
   List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
   // 扩展切面,这个是因为有一些切面比较老,需要去兼容一些,做一些适配
   extendAdvisors(eligibleAdvisors);
   if (!eligibleAdvisors.isEmpty()) 
      // 切面排序,决定执行先后顺序
      eligibleAdvisors = sortAdvisors(eligibleAdvisors);
   
   return eligibleAdvisors;

获取Aspect所有的切面

对Aspect注解,进行解析,获取所有的Aspect注解,切面
以及表达式
org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator
主流程

@Override
protected List<Advisor> findCandidateAdvisors() 
   // 先调用父类接口,兼容父类
   List<Advisor> advisors = super.findCandidateAdvisors();
   // 获取Aspect注解的切面
   advisors.addAll(this.aspectJAdvisorsBuilder.buildAspectJAdvisors());
   return advisors;


// 获取增强列表, 
// 来自类:org.springframework.aop.aspectj.annotation.BeanFactoryAspectJAdvisorsBuilder
public List<Advisor> buildAspectJAdvisors() 
   List<String> aspectNames = this.aspectBeanNames;

   if (aspectNames == null) 
      // 加锁,防止重复操作
      synchronized (this) 
          aspectNames = this.aspectBeanNames;
           // double check 
         if (aspectNames == null) 
            List<Advisor> advisors = new LinkedList<Advisor>();
            aspectNames = new LinkedList<String>();
           // 由于Aspect注解本身无法直接识别,所以通过这种方式获取所有的已经
            // 这个地方会获取所有的bean,包含继承Object的子类,由于Asject注解,的类本身是没有类型的
            // 所以这里使用Object获取所有的,调用这个方法会进行缓存
            //所以没有直接调用this.beanFactory.getBeanDefinitionNames 这个方法
           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;
               
               // 判断是否有Aspect注解
               if (this.advisorFactory.isAspect(beanType)) 
                  aspectNames.add(beanName);
                  AspectMetadata amd = new AspectMetadata(beanType, beanName);
                  if (amd.getAjType().getPerClause().getKind() == PerClauseKind.SINGLETON) 
                     // 创建工厂类,这个工厂类只包含当前aspect一个beanName,为了后续生成advice使用
                    MetadataAwareAspectInstanceFactory factory =
                           new BeanFactoryAspectInstanceFactory(this.beanFactory, beanName);
                    // 解析Aspect注解的类,获取方法上面的注解,每个增强方法都是一个切面增强
                    // 具体的可以看下代码细节,比较简单就是解析 Around After before这些注解
                    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();
   
   List<Advisor> advisors = new LinkedList<Advisor>();
   for (String aspectName : aspectNames) 
      // 单例
      List<Advisor> cachedAdvisors = this.advisorsCache.get(aspectName);
      if (cachedAdvisors != null) 
         advisors.addAll(cachedAdvisors);
      
      else 
         // 非单例的每次都需要通过工厂类生成新的对象
         MetadataAwareAspectInstanceFactory factory = this.aspectFactoryCache.get(aspectName);
         advisors.addAll(this.advisorFactory.getAdvisors(factory));
      
   
   return advisors;

获取类里面的增强器

// 获取@aspect 注解类中的 advice 
@Override
public List<Advisor> getAdvisors(MetadataAwareAspectInstanceFactory aspectInstanceFactory) 
   Class<?> aspectClass = aspectInstanceFactory.getAspectMetadata().getAspectClass();
   String aspectName = aspectInstanceFactory.getAspectMetadata().getAspectName();
   validate(aspectClass);

   // We need to wrap the MetadataAwareAspectInstanceFactory with a decorator
   // so that it will only instantiate once.
   // 为了延迟初始化对象
   MetadataAwareAspectInstanceFactory lazySingletonAspectInstanceFactory =
         new LazySingletonAspectInstanceFactoryDecorator(aspectInstanceFactory);

   List<Advisor> advisors = new ArrayList<Advisor>();
   // 过滤掉pointCut 切面注解, 
   for (Method method : getAdvisorMethods(aspectClass)) 
      // 获取所有的注解方法, @around @before等
      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;

// 
@Override
public Advisor getAdvisor(Method candidateAdviceMethod, MetadataAwareAspectInstanceFactory aspectInstanceFactory,
      int declarationOrderInAspect, String aspectName) 

   validate(aspectInstanceFactory.getAspectMetadata().getAspectClass());

   AspectJExpressionPointcut expressionPointcut = getPointcut(
         candidateAdviceMethod, aspectInstanceFactory.getAspectMetadata().getAspectClass());
   if (expressionPointcut == null) 
      return null;
   
    // 这里会根据注解 @around before after 生成不同的advice实现类
   return new InstantiationModelAwarePointcutAdvisorImpl(expressionPointcut, candidateAdviceMethod,
         this, aspectInstanceFactory, declarationOrderInAspect, aspectName);


// 
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;
  // A singleton aspect.
      this.pointcut = this.declaredPointcut;
      this.lazy = false;
      // 这里进行advice的初始化
      this.instantiatedAdvice = instantiateAdvice(this.declaredPointcut);
   

// 实例化增强器 advice
private Advice instantiateAdvice(AspectJExpressionPointcut pcut) 
                return this.aspectJAdvisorFactory.getAdvice(this.aspectJAdviceMethod, pcut,
                                this.aspectInstanceFactory, this.declarationOrder, this.aspectName);
        
// 根据不同的注解,生成不同的advice实例,代理的时候调用的是这个实例        
@Override
public Advice getAdvice(Method candidateAdviceMethod, AspectJExpressionPointcut expressionPointcut,
      MetadataAwareAspectInstanceFactory aspectInstanceFactory, int declarationOrder, String aspectName) 

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

   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;

   switch (aspectJAnnotation.getAnnotationType()) 
      case AtPointcut:
         if (logger.isDebugEnabled()) 
            logger.debug("Processing pointcut '" + candidateAdviceMethod.getName() + "'");
         
         return null;
         // around 注解,
      case AtAround:
         // 这里把facotyr作为参数放进去,是为了延迟获取实例化对象,等需要的时候再生成
         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);
   String[] argNames = this.parameterNameDiscoverer.getParameterNames(candidateAdviceMethod);
   if (argNames != null) 
      springAdvice.setArgumentNamesFromStringArray(argNames);
   
   springAdvice.calculateArgumentBindings();

   return springAdvice;

获取符合当前bean的切面

pointCut表达式文档

// 匹配符合条件的切面
protected List<Advisor> findAdvisorsThatCanApply(
      List<Advisor> candidateAdvisors, Class<?> beanClass, String beanName) 

   // 设置到 ThrealLocal里面,其他地方会调用这个来进行切面的匹配,从这里获取要增强的类
   // 决定是否要进行增强

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