首页 > 文章列表 > 关于Spring的AnnotationAwareAspectJAutoProxyCreator类解析

关于Spring的AnnotationAwareAspectJAutoProxyCreator类解析

java
220 2023-05-12

通过查看@EnableAspectJAutoProxy 注解的源码,如下所示。

package org.springframework.context.annotation;

import java.lang.annotation.Documented;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

@Target(ElementType.TYPE)

@Retention(RetentionPolicy.RUNTIME)

@Documented

@Import(AspectJAutoProxyRegistrar.class)

public @interface EnableAspectJAutoProxy {

 boolean proxyTargetClass() default false;

 boolean exposeProxy() default false;

}

得知,@EnableAspectJAutoProxy注解是通过使用@Import(AspectJAutoProxyRegistrar.class) 给容器中注册一个名字叫做internalAutoProxyCreator = AnnotationAwareAspectJAutoProxyCreator的组件。

并且我们也分析了AnnotationAwareAspectJAutoProxyCreato类的核心继承关系,如下所示。

  AnnotationAwareAspectJAutoProxyCreator

       --AspectJAwareAdvisorAutoProxyCreator

         --AbstractAdvisorAutoProxyCreator

           --AbstractAutoProxyCreator

             -- ProxyProcessorSupport, SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware

查看继承关系可以发现,此类实现了AwareBeanPostProcessor接口,这两个接口都和Spring bean的初始化有关,由此推测此类主要处理方法都来自这两个接口的实现方法。同时该类也实现了order方法。

那今天,我们就来看看AnnotationAwareAspectJAutoProxyCreator 类的调用流程,具体来说,就是看看 ``AnnotationAwareAspectJAutoProxyCreator` 作为BeanPostProcessor做了哪些工作,作为BeanFactoryAware做了哪些工作。

分析AbstractAutoProxyCreator类

AnnotationAwareAspectJAutoProxyCreator类的继承关系上可以看出, 是在AbstractAutoProxyCreator类开始实现 SmartInstantiationAwareBeanPostProcessor接口和 BeanFactoryAware 接口的。

所以,我们先来看看 AbstractAutoProxyCreator 类进行分析。

AbstractAutoProxyCreator 类的定义我们可以看出,AbstractAutoProxyCreator类直接实现了SmartInstantiationAwareBeanPostProcessor 接口和 BeanFactoryAware 接口。

public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport

		implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {

既然 AbstractAutoProxyCreator 实现了 BeanFactoryAware 接口, 那么 AbstractAutoProxyCreator 类中就一定存在setBeanFactory()方法,如下所示。

@Override

public void setBeanFactory(BeanFactory beanFactory) {

    this.beanFactory = beanFactory;

}

@Nullable

protected BeanFactory getBeanFactory() {

    return this.beanFactory;

}

果然,我们在 AbstractAutoProxyCreator 类中找到了setBeanFactory()方法和getBeanFactory()方法。

另外,在 AbstractAutoProxyCreator 类中还存在与BeanPostProcessor后置处理器有关的方法,分别为:postProcessBeforeInstantiation()、postProcessAfterInstantiation()、postProcessProperties()、postProcessBeforeInitialization()、postProcessAfterInitialization()。整体源代码如下所示。

@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;

        }

    }

    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;

    }

    return null;

}

@Override

public boolean postProcessAfterInstantiation(Object bean, String beanName) {

    return true;

}

@Override

public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {

    return pvs;

}

@Override

public Object postProcessBeforeInitialization(Object bean, String beanName) {

    return bean;

}

@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;

}

也就是说,在AbstractAutoProxyCreator 类中,存在后置处理器的逻辑。

到这,我们就在AbstractAutoProxyCreator 类中看到了BeanFactoryAware 的实现和后置处理器的实现。

接下来,我们再来看看AbstractAutoProxyCreator 的子类 AbstractAdvisorAutoProxyCreator类。

分析AbstractAdvisorAutoProxyCreator类

AbstractAdvisorAutoProxyCreator类中,我们会看到如下代码。

@Override

public void setBeanFactory(BeanFactory beanFactory) {

    super.setBeanFactory(beanFactory);

    if (!(beanFactory instanceof ConfigurableListableBeanFactory)) {

        throw new IllegalArgumentException(

            "AdvisorAutoProxyCreator requires a ConfigurableListableBeanFactory: " + beanFactory);

    }

    initBeanFactory((ConfigurableListableBeanFactory) beanFactory);

}

说明在AbstractAdvisorAutoProxyCreator类中重写了setBeanFactory()方法。并且在AbstractAdvisorAutoProxyCreator类的setBeanFactory()方法中,首先会调用AbstractAutoProxyCreator 类中的setBeanFactory()方法。

在setBeanFactory()方法中会调用initBeanFactory()方法,initBeanFactory()方法的实现如下所示。

protected void initBeanFactory(ConfigurableListableBeanFactory beanFactory) {

    this.advisorRetrievalHelper = new BeanFactoryAdvisorRetrievalHelperAdapter(beanFactory);

}

initBeanFactory()方法的实现比较简单,这里,我就不多说了。

另外,我们并没有在AbstractAdvisorAutoProxyCreator类中找到与后置处理器相关的方法。

接下来,我们继续分析AbstractAdvisorAutoProxyCreator类的子类AspectJAwareAdvisorAutoProxyCreator类。

分析AspectJAwareAdvisorAutoProxyCreator类

通过查看AspectJAwareAdvisorAutoProxyCreator类的源码,我们得知,在 AspectJAwareAdvisorAutoProxyCreator类中没有与后置处理器相关的代码。所以,我们继续向上分析 AspectJAwareAdvisorAutoProxyCreator类的子类 AnnotationAwareAspectJAutoProxyCreator

分析AnnotationAwareAspectJAutoProxyCreator类

AnnotationAwareAspectJAutoProxyCreator类中,我们可以找到一个initBeanFactory()方法,如下所示。

@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);

}

看到这里,小伙伴们对于setBeanFactory的调用流程有点清晰了吧?其实setBeanFactory()的调用流程为:首先会执行 AbstractAdvisorAutoProxyCreator类中的setBeanFactory()方法,在AbstractAdvisorAutoProxyCreator类中的setBeanFactory()方法中会调用其父类AbstractAutoProxyCreator 中的setBeanFactory()方法,然后在AbstractAdvisorAutoProxyCreator类中的setBeanFactory()方法中调用initBeanFactory()方法。由于在子类AnnotationAwareAspectJAutoProxyCreator中重写了initBeanFactory()方法,最终调用的就是AnnotationAwareAspectJAutoProxyCreator类中的initBeanFactory()方法。这么说有点绕,我们来看一张图吧。

注意,上图中的AbstractAdvisorAutoProxyCreator类中的setBeanFactory()方法作为程序调用的入口,它会依次调用AbstractAutoProxyCreator#setBeanFactory()AnnotationAwareAspectJAutoProxyCreator#initBeanFactory() ,然后,再由 AnnotationAwareAspectJAutoProxyCreator#initBeanFactory() 调用 AbstractAdvisorAutoProxyCreator#initBeanFactory()

除此之外,我们在AnnotationAwareAspectJAutoProxyCreator类中,并没有发现与后置处理器相关的代码了。