Spring容器创建之后，会调用它的refresh方法刷新Spring应用的上下文
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
// 调用Bean工厂的后置处理器:所有BeanFactoryPostProcessor（包括其子类 BeanDefinitionRegistryPostProcessor）
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// 初始化事件多播器：给事件监听器广播
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// 注册事件监听器
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}1、多播器和事件监听机制
initApplicationEventMulticaster：往容器中加一个多播器(用来派发事件)
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 检查beanFactory中是否已经存在了多播器
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
// 存在给多播放器赋值
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isDebugEnabled()) {
logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
// 不存在则自己new 一个SimpleApplicationEventMulticaster多播器
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
// 多播器注册到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 + "]");
}
}
}registerListeners：注册事件
protected void registerListeners() {
// 1、把容器中自带的监听器拿出来，注册到多播器中去
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// 2、把自定义的事件监听器取出来，注册到多播器中去（把所以继承类ApplicationListener的类全部找出来）
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// 有没有早期待处理的事件，有就调用多播器进行，播报事件
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}早期事件就是在initApplicationEventMulticaster前就创建的事件，也就是在多播器还没有创建好就创建的事件，initApplicationEventMulticaster就是一个分水岭。之前的为早期事件，后面的就不是了（SpringBoot 在onRefresh 会创建一些早期事件）
调用监听器中的方法进行多播
// 调用监听器中的方法进行多播
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);
}
}
}
@SuppressWarnings({"unchecked", "rawtypes"})
private void doInvokeListener(ApplicationListener listener, ApplicationEvent event) {
try {
listener.onApplicationEvent(event);
}
catch (ClassCastException ex) {
String msg = ex.getMessage();
if (msg == null || matchesClassCastMessage(msg, event.getClass())) {
// Possibly a lambda-defined listener which we could not resolve the generic event type for
// -> let's suppress the exception and just log a debug message.
Log logger = LogFactory.getLog(getClass());
if (logger.isDebugEnabled()) {
logger.debug("Non-matching event type for listener: " + listener, ex);
}
}
else {
throw ex;
}
}
}2、调用Bean工厂的后置处理器
invokeBeanFactoryPostProcessors(beanFactory)
本方法会实例化和调用所有 BeanFactoryPostProcessor（包括其子类 BeanDefinitionRegistryPostProcessor）
BeanFactoryPostProcessor（触发时机：bean定义注册之后bean实例化之前）和BeanDefinitionRegistryPostProcessor（触发时机：bean定义注册之前），继承自 BeanFactoryPostProcessor，比 BeanFactoryPostProcessor 具有更高的优先级，所以可以在Bean工厂的后置处理器中修改Bean的定义信息，比如是否延迟加载、加入一些新的Bean的定义信息等
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// getBeanFactoryPostProcessors(): 拿到当前应用上下文beanFactoryPostProcessors变量中的值（默认为空）
// 实例化并调用所有已注册的BeanFactoryPostProcessor
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<String>();
// 1.判断beanFactory是否为BeanDefinitionRegistry，beanFactory为DefaultListableBeanFactory，这边为ture
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// 存放普通的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
// 存放BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
// 2.首先处理入参中的beanFactoryPostProcessors
// 遍历将BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor区分开
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// 直接执行后置方法
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// 添加到registryProcessors(用于最后执行postProcessBeanFactory方法)
registryProcessors.add(registryProcessor);
} else {
// 添加到regularPostProcessors(用于最后执行postProcessBeanFactory方法)
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.
// 用于保存本次要执行的BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 3.调用所有实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor实现类
// 找出所有实现BeanDefinitionRegistryPostProcessor接口的Bean的beanName
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 获取bean实例, 添加到当前要执行的后置处理器中,
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
// 加入将要被执行的加入processedBeans，避免后续重复执行
processedBeans.add(ppName);
}
}
// 排序(根据是否实现PriorityOrdered、Ordered接口和order值来排序)
sortPostProcessors(currentRegistryProcessors, beanFactory);
// 添加到registryProcessors(用于最后执行postProcessBeanFactory方法)
registryProcessors.addAll(currentRegistryProcessors);
// 遍历当前要执行的后置处理器, 执行postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// 执行后, 清空当前要执行的后置处理器
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// 4.调用所有实现了Ordered接口的BeanDefinitionRegistryPostProcessor实现类（过程跟上面的步骤3基本一样）
// 找出所有实现BeanDefinitionRegistryPostProcessor接口的类, 重复查找是因为执行完上面的后置处理器可能会新增其他的后置处理器
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 校验是否实现了Ordered接口，并且还未执行过
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);
// 遍历当前要执行的后置处理器, 执行postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// 5.最后, 调用所有剩下的BeanDefinitionRegistryPostProcessors(没有实现PriorityOrdered和Ordered的)
boolean reiterate = true;
while (reiterate) {
reiterate = false;
// 找出所有实现BeanDefinitionRegistryPostProcessor接口的类
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 跳过已经执行过的
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
// 如果有BeanDefinitionRegistryPostProcessor被执行, 则有可能会产生新的BeanDefinitionRegistryPostProcessor,
// 因此这边将reiterate赋值为true, 代表需要再循环查找一次
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 遍历当前要执行的后置处理器, 执行postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 6.调用所有BeanDefinitionRegistryPostProcessor的postProcessBeanFactory方法(BeanDefinitionRegistryPostProcessor继承自BeanFactoryPostProcessor)
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// 7.最后, 调用入参beanFactoryPostProcessors中的普通BeanFactoryPostProcessor的postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
} else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// 到这里 , 入参beanFactoryPostProcessors和容器中的所有BeanDefinitionRegistryPostProcessor已经全部处理完毕,
// 下面开始处理容器中的所有BeanFactoryPostProcessor
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// 8.找出所有实现BeanFactoryPostProcessor接口的类
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 用于存放实现了PriorityOrdered接口的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
// 用于存放实现了Ordered接口的BeanFactoryPostProcessor的beanName
List<String> orderedPostProcessorNames = new ArrayList<String>();
// 用于存放普通BeanFactoryPostProcessor的beanName
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
// 遍历postProcessorNames, 将BeanFactoryPostProcessor按实现PriorityOrdered、实现Ordered接口、普通三种区分开
for (String ppName : postProcessorNames) {
// 跳过已经执行过的
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
} else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 添加实现了PriorityOrdered接口的BeanFactoryPostProcessor
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
} else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
// 添加实现了Ordered接口的BeanFactoryPostProcessor的beanName
orderedPostProcessorNames.add(ppName);
} else {
// 添加剩下的普通BeanFactoryPostProcessor的beanName
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
// 9.调用所有实现PriorityOrdered接口的BeanFactoryPostProcessor
// 排序
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
// 遍历执行postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
// 10.调用所有实现Ordered接口的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : orderedPostProcessorNames) {
// 获取postProcessorName对应的bean实例, 添加到orderedPostProcessors, 准备执行
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
// 排序
sortPostProcessors(orderedPostProcessors, beanFactory);
// 遍历执行postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
// 11.调用所有剩下的BeanFactoryPostProcessor
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
// 遍历nonOrderedPostProcessors, 执行postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
// 12.清除元数据缓存（mergedBeanDefinitions、allBeanNamesByType、singletonBeanNamesByType），
// 因为后处理器可能已经修改了原始元数据，例如， 替换值中的占位符...
beanFactory.clearMetadataCache();
}