Spring AOP 源码分析

【阅读前提】: 需了解AOP注解开发流程:链接

一、注解 @EnableAspectJAutoProxy

在配置类中添加注解@EnableAspectJAutoProxy,便开启了AOP(面向切面编程) 功能。此注解也是了解AOP源码的入口。

java">@EnableAspectJAutoProxy
@Configuration
public class MainConfigOfAOP {

【1】@EnableAspectJAutoProxy是什么?我们进入注解,查看其源码如下:发现调用EnableAspectJAutoProxy类,同时使用 @Import注解向容器中导入 AspectJAutoProxyRegistrar 组件:作用是给容器中注册自定义的Bean

@Import(AspectJAutoProxyRegistrar.class)
public @interface EnableAspectJAutoProxy {

【2】进入AspectJAutoProxyRegistrar类,调用registerBeanDefinitions中的register...Necessary方法注册组件。

class AspectJAutoProxyRegistrar implements ImportBeanDefinitionRegistrar {
	@Override
	public void registerBeanDefinitions(
			AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {

             //向容器(registry)中注入组件	
             AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);

【3】 进入register...Necessary方法,通过源码分析:该方法向容器中注册一个AnnotationAwareAspectJAutoProxyCreator(支持注解模式的面向切面自动代理创建器)组件,其名称为internalAutoProxyCreator。需要注意的是其注册的是一个BeanDefinitionBean的定义信息,并没有实例化。后续分析时会说到) 。

//debug 进来后,发现cls参数的值等于 AnnotationAwareAspectJAutoProxyCreator 这个参数也是直接写死的,如下:。
//registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
@Nullable
private static BeanDefinition registerOrEscalateApcAsRequired(
		Class<?> cls, BeanDefinitionRegistry registry, @Nullable Object source) {

	Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
	//AUTO_PROXY_CREATOR_BEAN_NAME == internalAutoProxyCreator 
	//因第一次进来,所以容器中不存在 internalAutoProxyCreator 
	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;
	}
	//创建一个新的对象封装 cls
	RootBeanDefinition beanDefinition = new RootBeanDefinition(cls);
	beanDefinition.setSource(source);
	beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE);
	beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
	//将封装的cls对象注册到容器中,并将名称定义为AUTO_PROXY_CREATOR_BEAN_NAME == internalAutoProxyCreator 就上上述判断的语句。
	//此时我们就应该分析 AnnotationAwareAspectJAutoProxyCreator对象的作用
	registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);
	return beanDefinition;
}

二、研究AnnotationAwareAspectJAutoProxyCreator

此自动代理创建器的内部功能,其等价于AOP的主要功能。 此类的继承结构如下:

我们进入自动代理的抽象父类AbstractAutoProxyCreator中发现,其实现了SmartInstantiationAwareBeanPostProcessor后置处理器(在bean初始化前后做一些操作,AOP的特点)和BeanFactoryAware自动装配BeanFactory

@SuppressWarnings("serial")
public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport
		implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {

AOP原理分析技巧:【看给容器中注册了什么组件, 这个组件什么时候工作,这个组件的功能是什么?】,研究透这些,原理也就清楚了。

我们从AbstractAutoProxyCreator父类向AnnotationAwareAspectJAutoProxyCreator子类的顺序,查看其内部关于后置处理器和自动装备的方法并加入断点:

【1】AbstractAutoProxyCreator:包含后置处理器前后的两个方法和自动装配的方法。

//后置处理器相关的方法1
@Override
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) {
	Object cacheKey = getCacheKey(beanClass, beanName);

	if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
		if (this.advisedBeans.containsKey(cacheKey)) {
			return null;
		}
		if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
			this.advisedBeans.put(cacheKey, Boolean.FALSE);
			return null;
		}
	}

//后置处理器相关的方法2
@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
	if (bean != null) {
		Object cacheKey = getCacheKey(bean.getClass(), beanName);
		if (this.earlyProxyReferences.remove(cacheKey) != bean) {
			return wrapIfNecessary(bean, beanName, cacheKey);
		}
	}
	return bean;
}

//自动装备相关的方法
@Override
public void setBeanFactory(BeanFactory beanFactory) {
	this.beanFactory = beanFactory;
}

【2】AbstractAdvisorAutoProxyCreator:重写了setBeanFactory方法。

//自动装备方法
@Override
public void setBeanFactory(BeanFactory beanFactory) {
	super.setBeanFactory(beanFactory);
	if (!(beanFactory instanceof ConfigurableListableBeanFactory)) {
		throw new IllegalArgumentException(
				"AdvisorAutoProxyCreator requires a ConfigurableListableBeanFactory: " + beanFactory);
	}
	initBeanFactory((ConfigurableListableBeanFactory) beanFactory);
}

【3】对 2中的initBeanFactory方法进行了重写。

@Override
protected void initBeanFactory(ConfigurableListableBeanFactory beanFactory) {
	super.initBeanFactory(beanFactory);
	if (this.aspectJAdvisorFactory == null) {
		this.aspectJAdvisorFactory = new ReflectiveAspectJAdvisorFactory(beanFactory);
	}
	this.aspectJAdvisorsBuilder =
			new BeanFactoryAspectJAdvisorsBuilderAdapter(beanFactory, this.aspectJAdvisorFactory);
}

三、Debug 测试类流程梳理

【1】创建 IOC 容器,传入主配置类MainConfigOfAOP

//获取容器中的类
ApplicationContext ApplicationContext = 
                                    new AnnotationConfigApplicationContext(MainConfigOfAOP.class);

【2】调用AnnotationConfigApplicationContext构造器:注册配置类和刷新容器(创建容器中的所有Bean,类似于初始化容器)

public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
        //创建对象
	this();
        //注册配置类
	register(annotatedClasses);
        //刷新容器
	refresh();
}

【3】调用refresh方法:主要查看registerBeanPostProcessors(beanFactory); 方法,其作用是注册bean后置处理器,用方便来拦截bean的创建。

@Override
public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
        ....
	// 注册 bean 后置处理器,用来拦截 bean 的创建
	registerBeanPostProcessors(beanFactory);
        ....
}

【4】进入registerBeanPostProcessors调用的方法:先获取 IOC 容器中已经定义了的需要创建对象的所有后置处理器BeanPostProcessor(已定义:指我们在解析配置类的时候@EnableAspectJAutoProxy会为我们注册一个AnnotationAwareAspectJAutoProxyCreator后置处理器的定义,包括默认的一些后置处理器的定义)例如:

上述列表中的internalAutoProxyCreator后置处理器,就是我们分析@EnableAspectJAutoProxy时注入的那个处理器。后置处理的注册分为以下三种情况:
 ■ 优先注册实现了PriorityOrdered(优先级)接口的BeanPostProcessors
 ■ 其次注册实现了Ordered接口的BeanPostProcessors
 ■ 注册所有常规Beanpstprocessors
internalAutoProxyCreator后置处理器实现了Ordered接口。分析代码可知:【根据bean定义名称internalAutoProxyCreatorbeanFactory中获取注入的后置处理器】调用的方法 = beanFactory.getBean(ppName, BeanPostProcessor.class);

public static void registerBeanPostProcessors(
			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
    //获取ioc容器中已经定义了的需要创建对象的所有 BeanPostProcessor
    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

    //也会注意一些其他后置处理器,bean 是在 beanPostProcessor 实例化期间创建的,即 bean 不适合由所有 beanPostProcessors 处理。这个其实不重要,可以省略...
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 +    postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
    //判断哪些后置处理器配置了优先级
    for (String ppName : postProcessorNames) {
        if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
	    BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
	    priorityOrderedPostProcessors.add(pp);
	    if (pp instanceof MergedBeanDefinitionPostProcessor) {
	        internalPostProcessors.add(pp);
	    }
	}else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
	    orderedPostProcessorNames.add(ppName);
	}else {
	    nonOrderedPostProcessorNames.add(ppName);
	}
    }
    // 优先注册实现了 PriorityOrdered(优先级) 的 BeanPostProcessors
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // 其次注册实现了Ordered 接口的 BeanPostProcessors.
    List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
    for (String ppName : orderedPostProcessorNames) {
        //根据 bean定义的名称internalAutoProxyCreator 从 beanFactory 中获取注入的后置处理器
        BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
	orderedPostProcessors.add(pp);
	if (pp instanceof MergedBeanDefinitionPostProcessor) {
	    internalPostProcessors.add(pp);
	}
    }
    sortPostProcessors(orderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, orderedPostProcessors);

    // 注册所有常规beanpstprocessors。
    List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
        for (String ppName : nonOrderedPostProcessorNames) {
	    BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
	    nonOrderedPostProcessors.add(pp);
	    if (pp instanceof MergedBeanDefinitionPostProcessor) {
	        internalPostProcessors.add(pp);
	    }
	}
	registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

    // 最后,重新注册所有内部beanpstprocessors。
    sortPostProcessors(internalPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, internalPostProcessors);

【5】进入上述所说的beanFactory.getBean(ppName, BeanPostProcessor.class); 方法如下:因第一次进入容器,因此获取不到实例。会通过 getSingleton方法创建BeanPostProcessor的实例,并保存到容器中。

@Override
public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
	return doGetBean(name, requiredType, null, false);
}


//上述方法内部调用的是 doGetBean(name, requiredType, null, false); 代码如下:
@SuppressWarnings("unchecked")
protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
		@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
        //因为第一次获取,容器中不存在此实例。因此 sharedInstance==null
	Object sharedInstance = getSingleton(beanName);
	if (sharedInstance != null && args == null) {
        ...
        }else {
	    // 创建 bean 实例
	    if (mbd.isSingleton()) {
	        sharedInstance = getSingleton(beanName, () -> {
	        try {
		    return createBean(beanName, mbd, args);
	        }catch (BeansException ex) {
		    destroySingleton(beanName);
		    throw ex;
	        }
	    });
	    bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
	    }
    }

【6】创建internalAutoProxyCreatorAnnotationAwareAspectJAutoProxyCreator实例。步骤如下:

//1、创建bean的实例
createBean(beanName, mbd, args);
//2、给Bean 的各属性赋值
populateBean(beanName, mbd, instanceWrapper);
//3、初始化 bean ,比较重要,因为后置处理器就是在此前后进行工作的
exposedObject = initializeBean(beanName, exposedObject, mbd);

【7】重点是:初始化initializeBean方法,查看实现的步骤如下:

//1、调用 invokeAwareMethods 处理Aware 接口的方法回调,beanName=internalAutoProxyCreator 实现了 BeanAware 接口
invokeAwareMethods(beanName, bean);
//2、应用后置处理器 BeforeInitialization
applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
//3、执行自定义的初始化方法
invokeInitMethods(beanName, wrappedBean, mbd);
//4、执行后置处理器的 After方法
applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);

//下面是上述方法的具体实现

//1、invokeAwareMethods 实现如下:
private void invokeAwareMethods(final String beanName, final Object bean) {
	if (bean instanceof Aware) {
                //.....
                //实现了 BeanFactoryAware 接口,因此执行 setBeanFactory.
                //bean==AnnotationAwareAspectJAutoProxyCreator
		if (bean instanceof BeanFactoryAware) {
			((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
		}
	}
}


//2、applyBeanPostProcessorsBeforeInitialization 实现如下:
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
    throws BeansException {

	Object result = existingBean;
        //获取所有的后置处理器,执行前置Before 处理器。
	for (BeanPostProcessor processor : getBeanPostProcessors()) {
		Object current = processor.postProcessBeforeInitialization(result, beanName);
		if (current == null) {
			return result;
		}
		result = current;
	}
	return result;
}

//3、invokeInitMethods 方法的具体实现
protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd)
		throws Throwable {

	boolean isInitializingBean = (bean instanceof InitializingBean);
	if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
		if (logger.isTraceEnabled()) {
			logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
		}
		if (System.getSecurityManager() != null) {
			try {
				AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
					((InitializingBean) bean).afterPropertiesSet();
					return null;
				}, getAccessControlContext());
			}
			catch (PrivilegedActionException pae) {
				throw pae.getException();
			}
		}
		else {
			((InitializingBean) bean).afterPropertiesSet();
		}
	}

	if (mbd != null && bean.getClass() != NullBean.class) {
		String initMethodName = mbd.getInitMethodName();
		if (StringUtils.hasLength(initMethodName) &&
				!(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
				!mbd.isExternallyManagedInitMethod(initMethodName)) {
			invokeCustomInitMethod(beanName, bean, mbd);
		}
	}
}

//4、applyBeanPostProcessorsAfterInitialization 具体实现
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
		throws BeansException {

	Object result = existingBean;
	for (BeanPostProcessor processor : getBeanPostProcessors()) {
		Object current = processor.postProcessAfterInitialization(result, beanName);
		if (current == null) {
			return result;
		}
		result = current;
	}
	return result;
}

【8】执行Aware初始化时,会调用setBeanFactory方法,我们追下去会发现调用的是AbstractAdvisorAutoProxyCreatorsetBeanFactory方法(就是我们分析AnnotationAwareAspectJAutoProxyCreator继承关系时的父类 )。

AnnotationAwareAspectJAutoProxyCreator(AbstractAdvisorAutoProxyCreator).setBeanFactory(BeanFactory)line:58
@Override
public void setBeanFactory(BeanFactory beanFactory) {
        //调用父类的 setBeanFactory
	super.setBeanFactory(beanFactory);
	if (!(beanFactory instanceof ConfigurableListableBeanFactory)) {
		throw new IllegalArgumentException(
				"AdvisorAutoProxyCreator requires a ConfigurableListableBeanFactory: " + beanFactory);
	}
        //AnnotationAwareAspectJAutoProxyCreator  方法对此进行了重写
	initBeanFactory((ConfigurableListableBeanFactory) beanFactory);
}

【9】进入initBeanFactory方法,我们知道此方法已被AnnotationAwareAspectJAutoProxyCreator重写:

//位于 AnnotationAwareAspectJAutoProxyCreator 类中
@Override
protected void initBeanFactory(ConfigurableListableBeanFactory beanFactory) {
	super.initBeanFactory(beanFactory);
	if (this.aspectJAdvisorFactory == null) {
                //创建了放射的通知工厂
		this.aspectJAdvisorFactory = new ReflectiveAspectJAdvisorFactory(beanFactory);
	}
	this.aspectJAdvisorsBuilder =
			new BeanFactoryAspectJAdvisorsBuilderAdapter(beanFactory, this.aspectJAdvisorFactory);
}

【10】最终BeanPostProcessor(AnnotationAwareAspectJAutoProxyCreator)创建成功,将其添加到beanFactory中。

for (String ppName : orderedPostProcessorNames) {
        //实例 pp==AnnotationAwareAspectJAutoProxyCreator 
	BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
        //放入 ordered后置处理器集合
	orderedPostProcessors.add(pp);
	if (pp instanceof MergedBeanDefinitionPostProcessor) {
		internalPostProcessors.add(pp);
	}
}
//将处理器按优先级排序
sortPostProcessors(orderedPostProcessors, beanFactory);
//调用注册方法
registerBeanPostProcessors(beanFactory, orderedPostProcessors);

//上述注册方法的内部代码
private static void registerBeanPostProcessors(
		ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
        //将后置处理器都添加到bean工厂
	for (BeanPostProcessor postProcessor : postProcessors) {
		beanFactory.addBeanPostProcessor(postProcessor);
	}
}

四、后置处理器创建后的操作

【1】以上是创建和注册AnnotationAwareAspectJAutoProxyCreator的过程。接下来就是对创建后的流程进行说明:AnnotationAwareAspectJAutoProxyCreator是继承InstantiationAwareBeanPostProcessor的后置处理器:我们在上面说的IOC容器初始化时,会调用 refresh方法:我们进入此方法看下,我们之前分析registerBeanPostProcessors方法,接下来分析finishBeanFactoryInitialization方法(实例所有剩余的单实例bean)完成BeanFactory初始化工作。

@Override
public void refresh() throws BeansException, IllegalStateException {
	synchronized (this.startupShutdownMonitor) {
	//......
	// 注册 bean后置处理器 来拦截 bean 的创建。
	registerBeanPostProcessors(beanFactory);
	//......
	// 初始化特定上下文子类中的其他特殊bean。
	onRefresh();
	//......
	// 实例化所有剩余的(非延迟初始化)单例。
	finishBeanFactoryInitialization(beanFactory);
}

【2】遍历获取容器中所有的Bean,依次创建对象 getBean(beanName); 流程:getBean->doGetBean()->getSingleton()getBean方法如下:先从缓存中获取当前bean,如果能获取到说明bean是之前被创建过的,直接使用,否则创建bean;只要是创建好的bean都会被缓存起来。

// 先检查单例缓存中是否有已存在手动注册的单例,如果存在说明之前bean已创建
Object sharedInstance = getSingleton(beanName);
//缓存中不存在 bean 时才创建该单例 bean
if (sharedInstance != null && args == null) {
	//...
}else{
	//创建bean实例。
	if (mbd.isSingleton()) {
		sharedInstance = getSingleton(beanName, () -> {
			try {
				return createBean(beanName, mbd, args);
			}
			catch (BeansException ex) {
				destroySingleton(beanName);
				throw ex;
			}
		});
		bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
	}
}

【2.1】进入创建bean的步骤:createBean方法,首先会调用resolveBeforeInstantiation方法,让beanPostProcessors后置处理器有机会返回代理对象而不是目标bean实例。如果能返回则直接使用,如果不能则调用doCreateBean方法来创建实例。

@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
			throws BeanCreationException {
        /*现获取类的基本信息 例如:
        Root bean: class [org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator]; 
        scope=singleton等等*/
        RootBeanDefinition mbdToUse = mbd;
	//......
	//让beanPostProcessors有机会返回代理而不是目标bean实例。		
	Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
	if (bean != null) {
		return bean;
	}
	//通过此方法,先调用 aware、前置处理器、bean初始化、后置处理器 ,之前有分析过。
	Object beanInstance = doCreateBean(beanName, mbdToUse, args);
}

BeanPostProcessor是在Bean对象创建完成初始化前后调用的】
InstantiationAwareBeanPostProcessor是在创建bean实例之前先尝试用后置处理器返回代理对象】
 后置处理器与后置处理器不同,具体什么时候调用,需要根据不同情况而定。

【2.1.1】分析resolveBeforeInstantiation方法(让beanPostProcessors有机会返回代理对象):我们分析的AnnotationAwareAspectJAutoProxyCreator就是InstantiationAwareBeanPostProcessor类型的后置处理器。会在任何bean创建之前先尝试返回bean的代理实例。

@Nullable
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
	bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
	if (bean != null) {
		bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
	}
}

//上面两个方法的源码展示
@Nullable
protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
	//获取所有的后置处理器
	for (BeanPostProcessor bp : getBeanPostProcessors()) {
		//如果后置处理器是 InstantiationAwareBeanPostProcessor 类型的处理器则执行 postProcessBeforeInstantiation 方法。
		//我们分析的 AnnotationAwareAspectJAutoProxyCreator 就是 InstantiationAwareBeanPostProcessor 类型的处理器
		if (bp instanceof InstantiationAwareBeanPostProcessor) {
			InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
			//***** 后续分析
			Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
			if (result != null) {
				return result;
			}
		}
	}
	return null;
}

【2.1.1.1】接着分析上述的postProcessBeforeInstantiation方法:内容较多,放在五中分析。

【2.1.2】分析doCreateBean方法,之前有介绍过,我们在看下源码:就是对创建的目标类前后对后置处理器的方法进行初始化。才是真正创建一个bean的实例。

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
			throws BeanCreationException {
    //创建 bean 实例
    instanceWrapper = createBeanInstance(beanName, mbd, args);
    //bean 属性赋值
    populateBean(beanName, mbd, instanceWrapper);
    //初始化 bean
    exposedObject = initializeBean(beanName, exposedObject, mbd);
}


//初始化方法 initializeBean 的源码
protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
	//初始化 aware 接口的类
	invokeAwareMethods(beanName, bean);
	//后置处理器 Before 方法初始化
	wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
	//初始化类
	invokeInitMethods(beanName, wrappedBean, mbd);
	//后置处理器 after 方法初始化
	wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
	//返回创建好的类
	return wrappedBean;
}

五、postProcessBeforeInstantiation方法分析

【1】每个bean创建之前,调用此方法。我们主要观察业务逻辑MathCalculator类和切面LogAspects类的创建。

//当bean = MathCalculator or LogAspects 我们着重分析此方法,其他的略过
@Override
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) {
	Object cacheKey = getCacheKey(beanClass, beanName);
        
	if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
                //判断当前 bean 是否在 advisedBeans 中(保存了所有需要增加的 bean:意思就是添加了切面的内容),第一次进行肯定是不包含的所以会跳过
		if (this.advisedBeans.containsKey(cacheKey)) {
			return null;
		}
                //isInfrastructureClass 判断当前类是否为基础类型的,也就是实现了 Advice、Pointcut、Advisor、AopInfrastructureBean 
                //或者是否为切面注解标注的类 (@Aspect),第一个 MathCalculator = false
                //shouldSkip 是否需要跳过:内部是获取候选的增强器(也就是切面内的通知方法)
                //将所有的增强器封装成了 List<Advisor> 集合,增强器的类型是 InstantiationModelAwarePointcutAdvisor
		if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
			this.advisedBeans.put(cacheKey, Boolean.FALSE);
			return null;
		}
	}
        // targetSource = null
	TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
	if (targetSource != null) {
		if (StringUtils.hasLength(beanName)) {
			this.targetSourcedBeans.add(beanName);
		}
		Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
		Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
		this.proxyTypes.put(cacheKey, proxy.getClass());
		return proxy;
	}
        //直接返回空,进入我们配置类中,创建 MathCalculator 对象
	return null;
}

【2】上述代码中的shouldSkip源码:

@Override
protected boolean shouldSkip(Class<?> beanClass, String beanName) {
	//获取所有的增强器 考虑通过缓存方面名称列表进行优化
	List<Advisor> candidateAdvisors = findCandidateAdvisors();
	for (Advisor advisor : candidateAdvisors) {
                //我们的增强器都是 InstantiationModelAwarePointcutAdvisor 类型的,不是AspectJPointcutAdvisor 所以跳过
		if (advisor instanceof AspectJPointcutAdvisor &&
				((AspectJPointcutAdvisor) advisor).getAspectName().equals(beanName)) {
			return true;
		}
	}
        //父类直接返回 false
	return super.shouldSkip(beanClass, beanName);
}

【3】创建完MathCalculator后,调用postProcessAfterInitialization

@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
	if (bean != null) {
                // cacheKey = calculator
		Object cacheKey = getCacheKey(bean.getClass(), beanName);
                //判断之前是否代理过
		if (this.earlyProxyReferences.remove(cacheKey) != bean) {
                        //包装目标类,如果需要的话
			return wrapIfNecessary(bean, beanName, cacheKey);
		}
	}
	return bean;
}

【3.1】查看包装方法wrapIfNecessary的源码:分析后得出如下结论:以后容器中获取到的就是这个组件的代理对象,执行目标方法的时候,代理对象就会执行通知方法的流程

protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
    //...... 省略的都是判断是否为切面类或以代理类
    //如果需要就创建代理类
    //getAdvicesAndAdvisorsForBean 获取能在当前类使用的增强器
    Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
    if (specificInterceptors != DO_NOT_PROXY) {
        //保存当前 bean 在advisedBeans 表示当前bean 被处理了
        this.advisedBeans.put(cacheKey, Boolean.TRUE);
        //创建代理对象 ****重点,返回的是一个通过 Cglib 代理的对象
	Object proxy = createProxy(
		bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
		this.proxyTypes.put(cacheKey, proxy.getClass());
		return proxy;
	}

	this.advisedBeans.put(cacheKey, Boolean.FALSE);
	return bean;

【3.1.1】进入当前类使用的增强器方法:getAdvicesAndAdvisorsForBean

@Override
@Nullable
protected Object[] getAdvicesAndAdvisorsForBean(
		Class<?> beanClass, String beanName, @Nullable TargetSource targetSource) {
        //获取可用的增强器
	List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName);
	if (advisors.isEmpty()) {
		return DO_NOT_PROXY;
	}
	return advisors.toArray();
}

【3.1.1.1】进入获取可用增强器的方法:findEligibleAdvisors

protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) {
        //获取后置增强器
	List<Advisor> candidateAdvisors = findCandidateAdvisors();
        //找到能在当前bean中使用的增强器(找那些方法能够切入到当前方法的)
	List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
	extendAdvisors(eligibleAdvisors);
	if (!eligibleAdvisors.isEmpty()) {
                //对增强器进行了排序
		eligibleAdvisors = sortAdvisors(eligibleAdvisors);
	}
	return eligibleAdvisors;
}

//上面获取当前bean中使用的增强器的方法源码
protected List<Advisor> findAdvisorsThatCanApply(
		List<Advisor> candidateAdvisors, Class<?> beanClass, String beanName) {

	ProxyCreationContext.setCurrentProxiedBeanName(beanName);
	try {
                //通过 AopUtils工具类获取所有的通知方法
		return AopUtils.findAdvisorsThatCanApply(candidateAdvisors, beanClass);
	}
	finally {
		ProxyCreationContext.setCurrentProxiedBeanName(null);
	}
}

//工具类方法源码展示
public static List<Advisor> findAdvisorsThatCanApply(List<Advisor> candidateAdvisors, Class<?> clazz) {
	if (candidateAdvisors.isEmpty()) {
		return candidateAdvisors;
	}
	List<Advisor> eligibleAdvisors = new ArrayList<>();
	for (Advisor candidate : candidateAdvisors) {
                //我们的增强器不是此类型
		if (candidate instanceof IntroductionAdvisor && canApply(candidate, clazz)) {
			eligibleAdvisors.add(candidate);
		}
	}
	boolean hasIntroductions = !eligibleAdvisors.isEmpty();
	for (Advisor candidate : candidateAdvisors) {
		if (candidate instanceof IntroductionAdvisor) {
			// already processed
			continue;
		}
                //判断增强器是否可用,我们的都是可用的
		if (canApply(candidate, clazz, hasIntroductions)) {
                        //将所有可以使用的增强器,加入到可用的增强器集合中
			eligibleAdvisors.add(candidate);
		}
	}
	return eligibleAdvisors;
}

//判断是否为可用的增强器的方法 canApply源码:
public static boolean canApply(Advisor advisor, Class<?> targetClass, boolean hasIntroductions) {
	if (advisor instanceof IntroductionAdvisor) {
		return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
	}
        //查看切面的方法是否都能匹配
	else if (advisor instanceof PointcutAdvisor) {
		PointcutAdvisor pca = (PointcutAdvisor) advisor;
		return canApply(pca.getPointcut(), targetClass, hasIntroductions);
	}
	else {
		// It doesn't have a pointcut so we assume it applies.
		return true;
	}
}

【3.1.2】进入代理对象的创建方法:createProxy

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

	if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
		AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
	}
        //创建代理工厂
	ProxyFactory proxyFactory = new ProxyFactory();
	proxyFactory.copyFrom(this);

	if (!proxyFactory.isProxyTargetClass()) {
		if (shouldProxyTargetClass(beanClass, beanName)) {
			proxyFactory.setProxyTargetClass(true);
		}
		else {
			evaluateProxyInterfaces(beanClass, proxyFactory);
		}
	}
        //获取所有的增强器,并保存在代理工厂
	Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
	proxyFactory.addAdvisors(advisors);
	proxyFactory.setTargetSource(targetSource);
	customizeProxyFactory(proxyFactory);

	proxyFactory.setFrozen(this.freezeProxy);
	if (advisorsPreFiltered()) {
		proxyFactory.setPreFiltered(true);
	}
        //使用代理工厂创建对象
	return proxyFactory.getProxy(getProxyClassLoader());
}

【3.1.2.1】进入代理工厂创建对象的方法proxyFactory.getProxy的源码:

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

//进入 createAopProxy().getProxy 内部的内部方法
@Override
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.");
		}
                //创建 JDK 代理或者 Cglib 代理。如果实现了接口则使用 JDK 代理,否则Cglib 代理
		if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
			return new JdkDynamicAopProxy(config);
		}
		return new ObjenesisCglibAopProxy(config);
	}
	else {
		return new JdkDynamicAopProxy(config);
	}
}

六、目标方法执行

【1】容器中保存了组件的代理对象(cglib增强后的对象),这个对象里面保存了详细信息(比如:增强器,目标对象…)

【2】CglibAopProxy.intercept(); 拦截目标方法执行如下:主要是根据ProxyFactory对象获取将要执行的目标方法的拦截器链。
 1)、如果没有拦截器链,直接执行目标方法。
 2)、如果有拦截器链,吧需要执行的目标对象,目标方法,拦截器链等信息传入创建一个CglibMethodInvocation对象,并调用retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed(); 方法。

@Override
@Nullable
public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
	Object oldProxy = null;
	boolean setProxyContext = false;
	Object target = null;
	TargetSource targetSource = this.advised.getTargetSource();
	try {
		if (this.advised.exposeProxy) {
			oldProxy = AopContext.setCurrentProxy(proxy);
			setProxyContext = true;
		}
		target = targetSource.getTarget();
		Class<?> targetClass = (target != null ? target.getClass() : null);
                //根据 ProxyFactory 对象获取将要执行的目标方法的拦截器链
		List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
		Object retVal;
                //如果没有拦截器链,直接执行目标方法。
		if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) {
			Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
			retVal = methodProxy.invoke(target, argsToUse);
		}
                //如果有拦截器链,吧需要执行的目标对象,目标方法,拦截器链等信息传入创建一个 CglibMethodInvocation 对象,并调用如下方法。
		else {
			retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();
		}
		retVal = processReturnType(proxy, target, method, retVal);
		return retVal;
	}
	finally {
		//......
	}
}

【3】 拦截器链:List<Object> chain = advised.getInterceptorsAndDynamicInterceptionAdvice的源码展示:
 1)、List<Object> interceptorList中保存了所有拦截器,总计5个。一个默认的ExposeInvocationInterceptor和 4个增强器。
 2)、遍历所有的增强器,将其转为Interceptor(拦截器):registry.getInterceptors(advisor);

@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
		Advised config, Method method, @Nullable Class<?> targetClass) {

	//......
	//获取所有的增强器进行遍历
	for (Advisor advisor : advisors) {
		//判断是否为切面的增强器
		if (advisor instanceof PointcutAdvisor) {
			//......
                        //将增强器转化为 MethodInterceptor
                        MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
                        if (mm.isRuntime()) {
				for (MethodInterceptor interceptor : interceptors) {
					interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
				}
			}
			else {
				interceptorList.addAll(Arrays.asList(interceptors));
			}
		}
		else if (advisor instanceof IntroductionAdvisor) {
			IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
			if (config.isPreFiltered() || ia.getClassFilter().matches(actualClass)) {
				Interceptor[] interceptors = registry.getInterceptors(advisor);
				interceptorList.addAll(Arrays.asList(interceptors));
			}
		}
		else {
			Interceptor[] interceptors = registry.getInterceptors(advisor);
			interceptorList.addAll(Arrays.asList(interceptors));
		}
	}

	return interceptorList;
}

 3)、将增强器转为MethodInterceptor,转化方式如下:最终返回拦截器链(每一个通知方法又被包装为方法拦截器,后期都是利用MethodInterceptor机制)。

@Override
public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
	List<MethodInterceptor> interceptors = new ArrayList<>(3);
	Advice advice = advisor.getAdvice();
        //如果是 MethodInterceptor 直接加入到 list 中
	if (advice instanceof MethodInterceptor) {
		interceptors.add((MethodInterceptor) advice);
	}
        //如果不是则,使用 AdvisorAdapter 将增强器转为 MethodInterceptor
	for (AdvisorAdapter adapter : this.adapters) {
		if (adapter.supportsAdvice(advice)) {
			interceptors.add(adapter.getInterceptor(advisor));
		}
	}
	if (interceptors.isEmpty()) {
		throw new UnknownAdviceTypeException(advisor.getAdvice());
	}
	return interceptors.toArray(new MethodInterceptor[0]);
}

【4】拦截器链有了之后,创建CglibMethodInvocation并执行proceed方法:

retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();

七、拦截器链的触发过程

【1】拦截器链展示:除了默认的方法ExposeInvocationInterceptor剩下的 4个都是我们切面中的方法。

【2】如果没有拦截器执行目标方法执行代理对象CglibMethodInvocationproceed方法:

retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();

【3】进入proceed方法:

@Override
@Nullable
public Object proceed() throws Throwable {
	//判断连接器栏的长度是否 == 0,此方法会在拦截器链的最后一个链时调用
	if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
                //执行目标方式,输入为:MathCalculator...div...
		return invokeJoinpoint();
	}
	//获取下标=0的拦截器 ExposeInvocationInterceptor
	Object interceptorOrInterceptionAdvice =
			this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
	if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
		//下标0 跳过......
	}
	else {
		// this=ReflectiveMethodInvocation
		return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
	}
}

【4】进入[MethodInterceptor] interceptorOrInterceptionAdvice).invoke(this); 方法:会循环调用list中的拦截器,直到后置处理器:AspectJMethodBeforeAdvice

//ThreadLocal 线程共享数据 (共享 MethodInvocation)
private static final ThreadLocal<MethodInvocation> invocation =
		new NamedThreadLocal<>("Current AOP method invocation");

@Override
public Object invoke(MethodInvocation mi) throws Throwable {
	//获取 invocation 
	MethodInvocation oldInvocation = invocation.get();
        //将当前方法,放入 invocation
	invocation.set(mi);
	try {
                //执行 cglib 的proceed() 就获取到了下标为1的拦截器 AspectJAfterThrowingAdvice
		return mi.proceed();
	}
	finally {
                //执行后置通知
		invocation.set(oldInvocation);
	}
}

【5】 当advice=AspectJMethodBeforeAdvice后置处理器时,invoke方法如下:

@Override
public Object invoke(MethodInvocation mi) throws Throwable {
        //执行后置处理器的 before 方法
        //输出如下:div运行。。。@Before:参数列表是:{[2, 3]}
	this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis());
        //进入上述展示的 processd 方法,此时进入第一个判断语句,执行目标方法
	return mi.proceed();
}

【6】 后置处理器的After方法执行的invoke方法展示:最终执行结果的返回方法。

@Override
public Object invoke(MethodInvocation mi) throws Throwable {
	try {
		return mi.proceed();
	}
	finally {
                //执行 after 方法:div结束。。。@After
		invokeAdviceMethod(getJoinPointMatch(), null, null);
	}
}

【7】上述分析的流程图如下:根据链表循环向下执行,当最后一个后置处理器的before执行完成后,进行目标方法,并进行回流执行拦截器的目标方法。

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