开启掘金成长之旅！这是我参与「掘金日新计划 · 2 月更文挑战」的第 10 天，点击查看活动详情
public void refresh() throws BeansException, IllegalStateException {
synchronized(this.startupShutdownMonitor) {
try {
.....
// 6. 注册Bean的后置处理器
this.registerBeanPostProcessors(beanFactory);
// 7. 初始化MessageSource
this.initMessageSource();
// 8. 初始化事件发布器
this.initApplicationEventMulticaster();
// 9. 子类的多态onRefresh
this.onRefresh();
// 10. 注册监听器
this.registerListeners();
.....
}
}
}
六、注册Bean的后置处理器
这回会获取所有BeanPostProcessor进行排序和创建，对实现MergedBeanDefinitionPostProcessor接口的会放到最后。
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
//获取所有BeanPostProcessor
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.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
//按照PriorityOrdered，Ordered和普通的进行分类
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
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);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
//首先对实现PriorityOrdered接口的进行排序和创建
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
//接着对实现Ordered接口的进行排序和创建
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
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.
//然后创建普通的BeanPostProcessor
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
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.
//最后对实现MergedBeanDefinitionPostProcessor接口进行排序
sortPostProcessors(internalPostProcessors, beanFactory);
//重新注册实现实现MergedBeanDefinitionPostProcessor接口的BeanPostProcessor
//作用：就是将MergedBeanDefinitionPostProcessor放在最后
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).
//添加一个ApplicationListenerDetector执行器
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
最终会有多个BeanPostProcessor被放入容器中
6.1 AutowiredAnnotationBeanPostProcessor
主要作用：完成了Spring基本的属性注入功能(@Autowired、@Value 、@Inject 注解功能)
6.2 ApplicationListenerDetector
主要作用：添加和销毁监听器
七、初始化MessageSource
MessageSource是实现国际化的接口
protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 检查是否已经存在了MessageSource组件，如果有，直接赋值
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 + "]");
}
}
// 如果没有，创建一个，并注册到BeanFactory中
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 + "]");
}
}
}
它默认创建的实现类是 DelegatingMessageSource。它的功能比较简单：将字符串和参数数组格式化为一个国际化后的消息。
八、初始化事件发布器
这里会判断Bean工厂中是否有事件派发器，如果没有就会默认创建SimpleApplicationEventMulticaster派发器
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
//判断是否有事件发布器
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 {
//如果没有会创建默认的事件发布器
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() + "]");
}
}
}
九、子类的多态onRefresh
这里用的是模板方法,由子类实现。SpringBoot 在这里创建了Web服务器
protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
}
十、注册监听器
protected void registerListeners() {
// Register statically specified listeners first.
// 把所有的IOC容器中以前缓存好的一组ApplicationListener取出来，添加到事件派发器中
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!
// 拿到BeanFactory中定义的所有的ApplicationListener类型的组件全部取出，添加到事件派发器中
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...
// 10.1 发布早期应用程序事件
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
早期事件的发布时机：监听器被注册，但其余的单实例Bean还没有创建时。
默认情况下这里根本就没有早期事件：
早期事件的设计由来：留给开发者，在后置处理器和监听器都被创建好，其余的单实例Bean还没有创建时，提供一个预留的时机来处理一些额外的事情。
总结
- 创建容器中所有的BeanPostProcessor
- 初始化MessageSource
- 创建了事件发布器
- 将监听器放入事件发布器中并且发布了早期事件
