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本文主要涉及：Spring中Bean的后置处理加入容器过程。
6.registerBeanPostProcessors
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
在Spring中对于 BeanPostProcessor 的处理分为两个过程，对于内置的 BeanPostProcessor的子类的实现，添加到 IoC容器中，是通过refresh() 方法中的 prepareBeanFactory() 过程来完成的。比如 ApplicationContextAwareProcessor， ApplicationListenerDetector。对于 ImportAwareBeanPostProcessor 是在，处理 ConfigurationClassPostProcessor时，对 @Configuration注解的类生成CGLIB 代理的时候加入容器中的。最后，在Spring中对于 BeanPostProcessor的实现类的处理，是在 refresh() 方法中有一个步骤 registerBeanPostProcessors() 来完成注册的，如 BeanPostProcessorChecker，CommonAnnotationBeanPostProcessor 以及 AutowiredAnnotationBeanPostProcessor，CommonAnnotationBeanPostProcessor。这样，在容器初始化之处，没有自己实现 BeanPsotProcessor 的时候，容器中就包含了6个Bean的后置处理器的实现。其中对于 registerBeanPostProcessors() 方法的详细代码实现，下面一一分析：
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 获取BeanDefinitionMap中所有的BeanPostProcessor
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
/** * BeanPostProcessorChecker 是一个普通的信息打印，可能会有些情况 * 当spring 的配置中的后置处理器还没有被注册就已经开始了bean的初始化时 * 便会打印出 BeanPostProcessorChecker 中设定的值 */ int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length; // new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount) // 创建一个 默认的 PostProcessorRegistrationDelegate, BeanPostProcessorChecker 是 PostProcessorRegistrationDelegate // 中的一个静态的内部类 且实现了 BeanPostProcessor 接口 beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount)); /** * 使用priorityOrdered 保证顺序 */ List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>(); List<BeanPostProcessor> internalPostProcessors = new ArrayList<>(); /** * 使用 ordered 保证顺序 */ List<String> orderedPostProcessorNames = new ArrayList<>(); /** * 无序 BeanPostProcessor */ List<String> nonOrderedPostProcessorNames = new ArrayList<>(); 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); } } /** * 第一步，注册所有实现 PriorityOrdered 的 BeanPostProcessors */ sortPostProcessors(priorityOrderedPostProcessors, beanFactory); registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors); /** * 第二步，注册所有实现 Ordered 的 BeanPostProcessors */ List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(); for (String ppName : orderedPostProcessorNames) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); orderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } sortPostProcessors(orderedPostProcessors, beanFactory); registerBeanPostProcessors(beanFactory, orderedPostProcessors); /** * 第三步，注册无序 的 BeanPostProcessors */ 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); // Finally, re-register all internal BeanPostProcessors. /** * 注册所有 MergedBeanDefinitionPostProcessor 类型的 BeanPostProcessors */ sortPostProcessors(internalPostProcessors, beanFactory); registerBeanPostProcessors(beanFactory, internalPostProcessors); // Re-register post-processor for detecting inner beans as ApplicationListeners, // moving it to the end of the processor chain (for picking up proxies etc). beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext)); }
将Bean的后置处理器加入到容器中
public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
// Remove from old position, if any
this.beanPostProcessors.remove(beanPostProcessor);
// Track whether it is instantiation/destruction aware
if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) { this.hasInstantiationAwareBeanPostProcessors = true; } if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) { this.hasDestructionAwareBeanPostProcessors = true; } // Add to end of list this.beanPostProcessors.add(beanPostProcessor); }
至此，Spring 中容器初始化不部分的解析已经处理完了，到目前为止，容器的中的东西基本上已经齐活了，通过下面的容器形成图示例： 
7.initMessageSource()
protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
// Make MessageSource aware of parent MessageSource.
if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) { HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource; if (hms.getParentMessageSource() == null) { // Only set parent context as parent MessageSource if no parent MessageSource // registered already. hms.setParentMessageSource(getInternalParentMessageSource()); } } if (logger.isTraceEnabled()) { logger.trace("Using MessageSource [" + this.messageSource + "]"); } } else { // Use empty MessageSource to be able to accept getMessage calls. DelegatingMessageSource dms = new DelegatingMessageSource(); dms.setParentMessageSource(getInternalParentMessageSource()); this.messageSource = dms; beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource); if (logger.isTraceEnabled()) { logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]"); } } }
判断beanFactory中是否有名字为messageSource的bean，如果有，从beanFactory中获取并且判断获取的是不是HierarchicalMessageSource类型的，如果是设置其父级消息源 如果没有，新建DelegatingMessageSource类作为messageSource的Bean。
8.initApplicationEventMulticaster()
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isTraceEnabled()) { logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]"); } } else { this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory); beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster); if (logger.isTraceEnabled()) { logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " + "[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]"); } } }
初始化 ApplicationEventMulticaster 如果用户自定义了事件广播器，那么使用用户自定义的事件广播器如果用户没有自定义事件广播器，那么使用默认的 ApplicationEventMulticaster 即 SimpleApplicationEventMulticaster.
9.onRefresh()
protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
}
空方法，Spring 预留给子类需要时来实现。
10.registerListeners();
protected void registerListeners() {
// Register statically specified listeners first.
// 硬编码的方式注册监听器的处理
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
} // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let post-processors apply to them! // 配置文件注册监听器的处理 String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false); for (String listenerBeanName : listenerBeanNames) { getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName); } // Publish early application events now that we finally have a multicaster... Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents; this.earlyApplicationEvents = null; if (earlyEventsToProcess != null) { for (ApplicationEvent earlyEvent : earlyEventsToProcess) { getApplicationEventMulticaster().multicastEvent(earlyEvent); } } }
获取容器中的监听器，然后得到当前容器中的 applicationEventMulticaster，调用 addApplicationListener进行添加。 这里的 applicationEventMulticaster 就是刚才初始化的，如果为空就是 SimpleApplicationEventMulticaster。
从BeanFactory中获取ApplicationListener类型的Bean，并且添加为ListenerBeans。
获取需要提前发布的事件，进行广播。
最后
至此， refresh()方法中的各个子方法的学习，仅剩了一个finishBeanFactoryInitialization()。关于这个方法，涉及到很多新的过程 并且与 Bean 的实例化过程息息相关。后面的文章将会介绍 Bean 的实例化。这里就是Bean的实例化入口的地方。
本文使用 mdnice 排版