【SpringIOC容器初始化（一）】
// 初始化BeanFactory，进行xml文件读取
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 对BeanFactory进行各种功能的填充
prepareBeanFactory(beanFactory);
try {
// 子类覆盖方法做其他的处理
postProcessBeanFactory(beanFactory);
// 激活BeanFactory的处理器
invokeBeanFactoryPostProcessors(beanFactory);
// 注册拦截Bean创建的Bean处理器
registerBeanPostProcessors(beanFactory);
// 为上下文初始化Message源
initMessageSource();
// 初始化应用消息广播器
initApplicationEventMulticaster();
// 留给子类初始化其他的bean
onRefresh();
// 查找Listeners bean,注册到消息广播器中
registerListeners();
// 初始化剩下的单实例
finishBeanFactoryInitialization(beanFactory);
// 完成刷新过程，通知生命周期处理器
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();
}
}
}
4.8 refresh中各个方法解析
protected void prepareRefresh() {
this.startupDate = System.currentTimeMillis();
this.closed.set(false);
this.active.set(true);
initPropertySources(); // 初始化配置文件
getEnvironment().validateRequiredProperties();
this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
}
..
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory(); // 这里对xml进行了解析，并且已经成功加入到map中了
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
return beanFactory; // 最终返回这个bean，就是DefaultListableBeanFactory对象，加载了xml的工厂
}
..
子类实现：
1、在bean工厂自动装配的时候忽略一些接口。如：ServletContextAware、ServletConfigAware
2、注册WEB应用特定的域（scope）到bean工厂中，以便WebApplicationContext可以使用它们。比如"request", "session", "globalSession", "application"，
3、注册WEB应用特定的Environment bean到bean工厂中，以便WebApplicationContext可以使用它们。如："contextParameters", "contextAttributes"
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());//主要是在这里面调用了所有的BeanFactoryPostProcessor
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
..
//初始化MessageSource接口的一个实现类。这个接口提供了消息处理功能。主要用于国际化/i18n。
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());
}
}
} 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);
}
}
..
//为这个context初始化一个事件广播器（ApplicationEventMulticaster）。
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {//’applicationEventMulticaster’ 检查是否给context配了一个ApplicationEventMulticaster实现类
this.applicationEventMulticaster =beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
}
else {//如果没有，就是用默认的实现类 SimpleApplicationEventMulticaster
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
}
}
..
protected void onRefresh() throws BeansException { // 子类实现.在AbstractApplicationContext的子类中初始化其他特殊的bean。其实就是初始化ThemeSource接口的实例。这个方法需要在所有单例bean初始化之前调用。
// For subclasses: do nothing by default.
}
protected void registerListeners() {//注册应用的监听器。就是注册实现了ApplicationListener接口的监听器bean，这些监听器是注册到ApplicationEventMulticaster中的。这不会影响到其它监听器bean。在注册完以后，还会将其前期的事件发布给相匹配的监听器。
// 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... 至此，已经完成将监听器注册到ApplicationEventMulticaster中，下面将发布前期的事件给监听器。
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
//完成bean工厂的初始化工作。这一步非常复杂，也非常重要，涉及到了bean的创建。第二步中只是完成了BeanDefinition的定义、解析、处理、注册。但是还没有初始化bean实例。这一步将初始化所有非懒加载的单例bean。这一步将会重新在一篇新的笔记中介绍。
//对配置了lazy-init属性的Bean进行预实例化处理
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context. 为容器指定一个转换服务(ConversionService) 在对某些Bean属性进行转换时使用
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(new StringValueResolver() {
@Override
public String resolveStringValue(String strVal) {
return getEnvironment().resolvePlaceholders(strVal);
}
});
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching. //为了类型匹配，停止使用临时的类加载器
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes. /缓存容器中所有注册的BeanDefinition元数据，以防被修改
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons. //对配置了lazy-init属性的单态模式Bean进行预实例化处理
beanFactory.preInstantiateSingletons();//DefaultListableBeanFactory对配置lazy-init属性的单例bean预实例化
}
...
//完成context的刷新。主要是调用LifecycleProcessor的onRefresh()方法，并且发布事件（ContextRefreshedEvent）
protected void finishRefresh() {
// Initialize lifecycle processor for this context.
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh();
// Publish the final event.
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
...
protected void resetCommonCaches() {
ReflectionUtils.clearCache();
ResolvableType.clearCache();
CachedIntrospectionResults.clearClassLoader(getClassLoader());
}
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