9 刷新IOC容器
此篇文章为springboot启动的下篇，紧接者上篇的刷新IOC容器
registerBeanPostProcessors(beanFactory)，代码比较简单如下，把所有实现了BeanPostProcessor接口的Bean实例按照优先级添加到beanFactory的beanPostProcessors属性当中（beanPostProcessors是一个列表），在方法最后添加了一个ApplicationListenerDetector，在Bean初始化完成之后，如果是一个ApplicationListener实例，则将实例添加到上下文的Listeners属性当中
代码语言：javascript复制public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() 1 postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
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);
}
}
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
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);
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);
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}initMessageSource()，初始换国际化的MessageSource，如果没有配置MessageSource，使用默认的DelegatingMessageSource
代码语言：javascript复制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 "]");
}
}
}initApplicationEventMulticaster()，比较简单，就是初始化了一个applicationEventMulticaster事件发布器
代码语言：javascript复制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() "]");
}
}
}onRefresh()，如下，父类的onRefresh方法主要设置了应用的主题，和MessageSource的使用类似，可以设置ThemeSource，主要用于UI界面的主题切换功能，接着创建了一个WebServer，默认是tomcat
代码语言：javascript复制protected void onRefresh() {
super.onRefresh();
try {
createWebServer();
}
catch (Throwable ex) {
throw new ApplicationContextException("Unable to start web server", ex);
}
}registerListeners()，如下，将context的ApplicationListeners注册到上文初始化的事件发布器ApplicationEventMulticaster当中
代码语言：javascript复制protected void registerListeners() {
// Register statically specified listeners first.
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!
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 (!CollectionUtils.isEmpty(earlyEventsToProcess)) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}finishBeanFactoryInitialization(beanFactory)，实例化所有非懒加载的Bean实例，最终是调用DefaultListable.preInstantiateSingletons()方法实例化，如下
代码语言：javascript复制public void preInstantiateSingletons() throws BeansException {
......
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// 加载所有非懒加载的Bean
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX beanName);
if (bean instanceof FactoryBean) {
FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(
(PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
getBean(beanName);
}
}
}
// 所有非懒加载Bean实例加载完成之后，Bean如果实现了SmartInitializingSingleton，调用其回调方法
// afterSingletonsInstantiated()，这个特性在xxl-job执行器的初始化中有使用过
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
StartupStep smartInitialize = getApplicationStartup().start("spring.beans.smart-initialize")
.tag("beanName", beanName);
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
smartInitialize.end();
}
}
}实例化的Bean的流程后续专门分析，这里先看个大概，实例化完成之后看看最后一步finishRefresh()，
代码语言：javascript复制protected void finishRefresh() {
// 清理一些资源的缓存
clearResourceCaches();
// 初始化LifecycleProcessor，从BeanFactory中获取LifecycleProcessor实例（没有就创建一个）
// 用来处理所有实现了Lifecycle接口的实例（Lifecycle接口主要有start，stop，isRunning三个方法）
initLifecycleProcessor();
// onRefresh方法就是从BeanFactory中获取有实现了Lifecycle接口的实例，依次调用其start方法
getLifecycleProcessor().onRefresh();
// 发布一个ContextRefreshedEvent事件
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
if (!NativeDetector.inNativeImage()) {
LiveBeansView.registerApplicationContext(this);
}
}至此刷新IOC容器就完成了
10 IOC容器刷新后处理
刷新后首先调用afterRefresh(context, applicationArguments)方法，默认是个空实现，然后调用了listeners.started(context, timeTakenToStartup)方法，关注第一行代码，通过上下文发布一个ApplicationStartedEvent事件
代码语言：javascript复制public void started(ConfigurableApplicationContext context, Duration timeTaken) {
context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context, timeTaken));
AvailabilityChangeEvent.publish(context, LivenessState.CORRECT);
}11 回调CommandRunner
最后获取容器中所有的实现了Runner接口的实例，回调其run方法，在elastic-job中定时的周期性任务就是通过此方式启动的
代码语言：javascript复制private void callRunners(ApplicationContext context, ApplicationArguments args) {
context.getBeanProvider(Runner.class).orderedStream().forEach((runner) -> {
if (runner instanceof ApplicationRunner) {
callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {
callRunner((CommandLineRunner) runner, args);
}
});
}至此容器启动流程结束
