1.BeanFactoryPostProcessor
/** * 允许自定义修改应用程序上下文的bean定义，调整上下文的基础bean工厂的bean属性值。 * * <p>应用程序上下文可以在其bean定义中自动检测BeanFactoryPostProcessor bean * ，并在创建任何其他bean之前应用它们。 * * BeanFactoryPostProcessor可以与bean定义交互并修改bean定义，但绝不能与bean实例交互。 * 这样做可能会导致bean过早实例化，违反容器并导致意外的副作用。 如果需要bean实例交互， * 请考虑实现{@link BeanPostProcessor} * * @author Juergen Hoeller * @since 06.07.2003 * @see BeanPostProcessor * @see PropertyResourceConfigurer */ public interface BeanFactoryPostProcessor { /** * 在标准初始化之后修改应用程序上下文的内部bean工厂。 * 将加载所有bean定义，但尚未实例化任何bean。 这允许覆盖或添加属性，甚至是初始化bean。 * @param beanFactory the bean factory used by the application context * @throws org.springframework.beans.BeansException in case of errors */ void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException; }3.BeanDefinitionRegistryPostProcessor
/** * Extension to the standard {@link BeanFactoryPostProcessor} SPI, allowing for * the registration of further bean definitions <i>before</i> regular * BeanFactoryPostProcessor detection kicks in. In particular, * BeanDefinitionRegistryPostProcessor may register further bean definitions * which in turn define BeanFactoryPostProcessor instances. * * {@link BeanFactoryPostProcessor}扩展接口,在常常规BeanFactoryPostProcessor检测开始之前 * 允许更多的bean definitions注册<i>before</i> * 特别的BeanDefinitionRegistryPostProcessor可以注册更多的bean definitions * 而bean定义又定义了BeanFactoryPostProcessor实例 * * @author Juergen Hoeller * @since 3.0.1 * @see org.springframework.context.annotation.ConfigurationClassPostProcessor */ public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor { /** * Modify the application context's internal bean definition registry after its * standard initialization. All regular bean definitions will have been loaded, * but no beans will have been instantiated yet. This allows for adding further * bean definitions before the next post-processing phase kicks in. * @param registry the bean definition registry used by the application context * @throws org.springframework.beans.BeansException in case of errors */ void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException; }3.分析invokeBeanFactoryPostProcessors(beanFactory);从字面上理解调用注册的BeanFactoryPostProcessor。
首先我们要清楚注册BeanFactoryPostProcessor有两种方式
方式一:配置的方式———编写BeanFactoryPostProcessor接口的实现类，然后配置到*.xml,
方式二:硬编码————AbstractApplicationContext提供了如下方法
@Override public void addBeanFactoryPostProcessor(BeanFactoryPostProcessor postProcessor) { Assert.notNull(postProcessor, "BeanFactoryPostProcessor must not be null"); this.beanFactoryPostProcessors.add(postProcessor); }深入到invokeBeanFactoryPostProcessors方法的实现中
public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { // Invoke BeanDefinitionRegistryPostProcessors first, if any. //如果有 BeanDefinitionRegistryPostProcessors 的话，调用 Set<String> processedBeans = new HashSet<String>(); //beanFactory支持注册bean定义 if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; //常规的beanFactoryPostProcessor List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>(); List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>(); for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { //如果为BeanDefinitionRegistryPostProcessor类型 if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; //事先调用下postProcessBeanDefinitionRegistry registryProcessor.postProcessBeanDefinitionRegistry(registry); //保存下registryPostProcessors registryProcessors.add(registryProcessor); } else { regularPostProcessors.add(postProcessor); } } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! // Separate between BeanDefinitionRegistryPostProcessors that implement // PriorityOrdered, Ordered, and the rest. //不要在这里初始化FactoryBeans：我们需要保留所有常规bean //未初始化让bean工厂的后处理器适用于它们 //区分BeanDefinitionRegistryPostProcessors为实现PriorityOrdered，Ordered和剩余的接口 //获取已经注册的postProcessor List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>(); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. //首先，调用实现PriorityOrdered的BeanDefinitionRegistryPostProcessors。这是可能通过xml配置注册的 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); //这些根据类型拿到的bean也需要后置处理，所以暂时保存起来 processedBeans.add(ppName); } } //排序获取已经注册的postProcessor sortPostProcessors(currentRegistryProcessors, beanFactory); //registryProcessors添加所有currentRegistryProcessors registryProcessors.addAll(currentRegistryProcessors); //调用 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered. // 调用那些实现Ordered的BeanDefinitionRegistryPostProcessors，这是可能通过xml配置注册的 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear. // 最后，调用所有其他BeanDefinitionRegistryPostProcessors，直到不再出现其他BeanDefinitionRegistryPostProcessors。 boolean reiterate = true; while (reiterate) { reiterate = false; postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); reiterate = true; } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); } // 现在，调用到目前为止处理的所有处理器的postProcessBeanFactory回调. invokeBeanFactoryPostProcessors(registryProcessors, beanFactory); invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); } else { // Invoke factory processors registered with the context instance. // 调用在上下文实例中注册的工厂处理器。 invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory); } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! //不要在这里初始化FactoryBeans：我们需要保留所有未初始化的常规bean，以使bean工厂后处理器适用于它们！ String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, // Ordered, and the rest. List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>(); List<String> orderedPostProcessorNames = new ArrayList<String>(); List<String> nonOrderedPostProcessorNames = new ArrayList<String>(); for (String ppName : postProcessorNames) { if (processedBeans.contains(ppName)) { // skip - already processed in first phase above //第一阶段已经处理过了 } else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class)); } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessorNames.add(ppName); } else { nonOrderedPostProcessorNames.add(ppName); } } // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered. sortPostProcessors(priorityOrderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // Next, invoke the BeanFactoryPostProcessors that implement Ordered. List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>(); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // Finally, invoke all other BeanFactoryPostProcessors. List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>(); for (String postProcessorName : nonOrderedPostProcessorNames) { nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory); // Clear cached merged bean definitions since the post-processors might have // modified the original metadata, e.g. replacing placeholders in values... beanFactory.clearMetadataCache(); }分析上面的代码我们只需要知道几个要点:
a.硬件编码的BeanFactoryPostProcessor或者BeanDefinitionRegistryPostProcessor总是先执行，其次才是xml中配置的b.对于硬件编码的BeanFactoryPostProcessor或者BeanDefinitionRegistryPostProcessor是按照添加顺序执行的c.beanFactory实现了BeanDefinitionRegistry接口,则需要先执行BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry;然后是xml中配置的BeanDefinitionRegistryPostProcessors，最后才是BeanFactoryPostProcessord.BeanDefinitionRegistryPostProcessor的postProcessBeanFactory总是先于BeanFactoryPostProcessor的postProcessBeanFactory执行e.BeanDefinitionRegistryPostProcessor的postProcessBeanFactory优先于BeanFactoryPostProcessor先执行f.执行顺序后置处理会按照有没有实现PriorityOrdered,Ordered的接口判断按照：PriorityOrdered>Ordered>正常的再去分析代码其实就很简单了
1.beanFactory继承自BeanDefinitionRegistry吗，是的话需要先查找到BeanDefinitionRegistryPostProcessor，先是硬编码进去的执行一次，并保存到一个列表中，用于放到后面执行他的postProcessBeanFactory方法；然后从xml配置中取到BeanDefinitionRegistryPostProcessor,按照先执行实现PriorityOrdered>Ordered>正常的顺序的，调用postProcessBeanDefinitionRegistry方法注册beanDefinition;然后执行BeanDefinitionRegistryPostProcessor类型的BeanFactoryPostProcessor的postProcessBeanFactory然后才是BeanFactoryPostProcessor的后处理器。2.如果beanFactory没有继承自BeanDefinitionRegistry则执行硬编码方式添加的BeanFactoryPostProcessor3.从xml配置中查找不包含在1，2两步中已经用过的BeanFactoryPostProcessor，然后按照顺序PriorityOrdered>Ordered>正常的，分别调用下去4.registerBeanPostProcessors(beanFactory);注册BeanPostProcessors
public static void registerBeanPostProcessors( ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) { //从beanFactory中获取BeanPostProcessor类型的beanNames String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false); // Register BeanPostProcessorChecker that logs an info message when // a bean is created during BeanPostProcessor instantiation, i.e. when // a bean is not eligible for getting processed by all BeanPostProcessors. // BeanPostProcessorChecker记录可能出现某些beanPostProcessors为注册但是bean已经初始化的状况 // 总数量 int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length; // 添加一个BeanPostProcessorChecker beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount)); // Separate between BeanPostProcessors that implement PriorityOrdered, // Ordered, and the rest. List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>(); // 内部的postProcessors 如MergedBeanDefinitionPostProcessor List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>(); List<String> orderedPostProcessorNames = new ArrayList<String>(); List<String> nonOrderedPostProcessorNames = new ArrayList<String>(); 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); } } // First, register the BeanPostProcessors that implement PriorityOrdered. // 按顺序注册优先级最高的beanPostProcessors sortPostProcessors(priorityOrderedPostProcessors, beanFactory); registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors); // Next, register the BeanPostProcessors that implement Ordered. // 按顺序注册实现ordered接口的BeanPostProcessors List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>(); 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); // Now, register all regular BeanPostProcessors. // 注册自然顺序的BeanPostProcessors List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>(); 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. // 最后 注册内部的MergedBeanDefinitionPostProcessor类型的internalPostProcessors 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). // 注册用于检测内部bean为ApplicationListeners的ApplicationListenerDetector // 将它移动到处理器链的末尾（用于拾取代理等） beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext)); } a.注册一个BeanPostProcessor,BeanPostProcessorChecker用于记录可能出现某些beanPostProcessors为注册但是bean已经初始化的状况b.按照顺序注册BeanPostProcessor,对于MergedBeanDefinitionPostProcessor类型的保存到集合中c.按照顺序PriorityOrdered>Ordered>正常 顺序挨个注册BeanPostProcessorsd.注册MergedBeanDefinitionPostProcessorse.注册检测内部bean为ApplicationListeners的ApplicationListenerDetector 将它移动到处理器链的末尾（用于拾取代理等）5.ApplicationEventMulticaster
a.ApplicationEventMulticaster:管理那些实现{@link ApplicationListener}接口的对象，并且向listener发布事件,相关方法addApplicationListener（）添加一个侦听器以通知所有事件、removeApplicationListener（）删除一个监听器、removeAllListeners（）删除所有的监听器、multicastEvent（）广播时间到适当的监听器b.AbstractApplicationEventMulticaster:{@link ApplicationEventMulticaster}接口的抽象实现，提供基本的监听器注册工具,默认情况下不允许出现多个相同的监听器的,因为AbstractApplicationEventMulticaster将 监听器保存到linkedHashSet6.initApplicationEventMulticaster()
/** * Initialize the ApplicationEventMulticaster. * Uses SimpleApplicationEventMulticaster if none defined in the context. * * 初始化ApplicationEventMulticaster,如果上下文中未定义 * 则使用SimpleApplicationEventMulticaster * @see org.springframework.context.event.SimpleApplicationEventMulticaster */ protected void initApplicationEventMulticaster() { //TODO 扩展点，查找beanFactory中是否有applicationEventMulticaster名称的bean，没有的话使用Spring提供的SimpleApplicationEventMulticaster ConfigurableListableBeanFactory beanFactory = getBeanFactory(); if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) { this.applicationEventMulticaster = beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class); if (logger.isDebugEnabled()) { logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]"); } } else { this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory); beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster); if (logger.isDebugEnabled()) { logger.debug("Unable to locate ApplicationEventMulticaster with name '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "': using default [" + this.applicationEventMulticaster + "]"); } } }由于ApplicationContext实现了ApplicationEventPublisher接口我们，所以可以通过使用ApplicationContext的publishEvent方法进行消息的发布事件
圈住的地方会获取到我们通过initApplicationEventMulticaster（）方法注册的ApplicationEventMulticaster，我们进入Spring给我们提供的默认的SimpleApplicationEventMulticaster.multicastEvent方法
@Override public void multicastEvent(final ApplicationEvent event, ResolvableType eventType) { ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event)); for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) { Executor executor = getTaskExecutor(); if (executor != null) { executor.execute(new Runnable() { @Override public void run() { invokeListener(listener, event); } }); } else { invokeListener(listener, event); } } }然后listeners就可以接收到消息了
