AspectJAwareAdvisorAutoProxyCreator及为Bean生成署理机缘阐明

上篇文章说了，org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator这个类是Spring提供应开拓者的AOP的焦点类，软件开发，就是AspectJAwareAdvisorAutoProxyCreator完成了【类/接口–>署理】的转换进程，首先我们看一下AspectJAwareAdvisorAutoProxyCreator的条理布局：

这里最值得留意的一点是最左下角的谁人方框，我用几句话总结一下：

1. AspectJAwareAdvisorAutoProxyCreator是BeanPostProcessor接口的实现类
2. postProcessBeforeInitialization要领与postProcessAfterInitialization要领实此刻父类AbstractAutoProxyCreator中
3. postProcessBeforeInitialization要领是一个空实现
4. 逻辑代码在postProcessAfterInitialization要领中

基于以上的阐明，将Bean生成署理的机缘已经一目了然了：在每个Bean初始化之后，假如需要，挪用AspectJAwareAdvisorAutoProxyCreator中的postProcessBeforeInitialization为Bean生成署理。

署理工具实例化—-判定是否为<bean>生成署理

上文阐明白Bean生成署理的机缘是在每个Bean初始化之后，下面把代码定位到Bean初始化之后，先是AbstractAutowireCapableBeanFactory的initializeBean要领举办初始化：

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
    if (System.getSecurityManager() != null) {
        AccessController.doPrivileged(new PrivilegedAction<Object>() {
            public Object run() {
                invokeAwareMethods(beanName, bean);
                return null;
            }
        }, getAccessControlContext());
    }
    else {
        invokeAwareMethods(beanName, bean);
    }

    Object wrappedBean = bean;
    if (mbd == null || !mbd.isSynthetic()) {
        wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
    }

    try {
    invokeInitMethods(beanName, wrappedBean, mbd);
    }
    catch (Throwable ex) {
        throw new BeanCreationException(
                (mbd != null ? mbd.getResourceDescription() : null),
                beanName, "Invocation of init method failed", ex);
    }

    if (mbd == null || !mbd.isSynthetic()) {
        wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
    }
    return wrappedBean;
}

初始化之前是第16行的applyBeanPostProcessorsBeforeInitialization要领，初始化之后即29行的applyBeanPostProcessorsAfterInitialization要领：

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
        throws BeansException {

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

这里挪用每个BeanPostProcessor的postProcessBeforeInitialization要领。凭据之前的阐明，看一下AbstractAutoProxyCreator的postProcessAfterInitialization要领实现：

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;
}

跟一下第5行的要领wrapIfNecessary：

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;
}

第2行~第11行是一些不需要生成署理的场景判定，这里略过。首先我们要思考的第一个问题是：哪些方针工具需要生成署理？因为设置文件内里有许多Bean，必定不能对每个Bean都生成署理，因此需要一套法则判定Bean是不是需要生成署理，这套法则就是第14行的代码getAdvicesAndAdvisorsForBean：

protected List<Advisor> findEligibleAdvisors(Class beanClass, String beanName) {
    List<Advisor> candidateAdvisors = findCandidateAdvisors();
    List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName);
    extendAdvisors(eligibleAdvisors);
    if (!eligibleAdvisors.isEmpty()) {
        eligibleAdvisors = sortAdvisors(eligibleAdvisors);
    }
    return eligibleAdvisors;
}

顾名思义，要领的意思是为指定class寻找符合的Advisor。