日期：2019-04-03
（7）initMessageSource
对上下文的消息源进行初始化
protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// messageSource 包含单例的话，检测属性是否设置
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;
// 父级消息源没有设置的，setParent
if (hms.getParentMessageSource() == null) {
// Only set parent context as parent MessageSource if no parent MessageSource
// registered already.
//如果没有父MessageSource，则仅将父上下文设置为父MessageSource
hms.setParentMessageSource(getInternalParentMessageSource());
}
}
if (logger.isDebugEnabled()) {
logger.debug("Using MessageSource [" + this.messageSource + "]");
}
}
//不包含消息源，创建
else {
// Use empty MessageSource to be able to accept getMessage .calls
DelegatingMessageSource dms = new DelegatingMessageSource();
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
//注册 messageSource 单例
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate MessageSource with name '" + MESSAGE_SOURCE_BEAN_NAME +
"': using default [" + this.messageSource + "]");
}
}
}
（8）initMessageSource
初始化ApplicationEventMulticaster。 如果在上下文中没有定义，则使用SimpleApplicationEventMulticaster。
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// APPLICATION_EVENT_MULTICASTER_BEAN_NAME = applicationEventMulticaster
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 + "]");
}
}
}
（9）initApplicationEventMulticaster
初始化上下文中的事件机制的容器
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// APPLICATION_EVENT_MULTICASTER_BEAN_NAME = applicationEventMulticaster
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 + "]");
}
}
}
（10）onRefresh
初始化其他的特殊bean，需要用户重写。这里为空。
protected void onRefresh() throws BeansException {
// For subclasses: do nothing by default.
}
（11） registerListeners
检查监听bean并且将这些bean向容器注册，比如Dubbo服务发布的过程就是在这个时候做的，利用事件发布机制，在listener.onApplicationEvent(event) 中发布暴露服务。
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 earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
//触发事件机制。多个事件同时触发。
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
multicastEvent方法调用 multicastEvent(event, resolveDefaultEventType(event)),然后调用 invokeListener(listener, event)，接着listener.onApplicationEvent(event); 触发事件。
/**
* SimpleApplicationEventMulticaster#multicastEvent(ApplicationEvent)
*/
public void multicastEvent(ApplicationEvent event) {
multicastEvent(event, resolveDefaultEventType(event));
}
@Override
public void multicastEvent(final ApplicationEvent event, ResolvableType eventType) {
ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
for (final ApplicationListener listener : getApplicationListeners(event, type)) {
//是否异步
Executor executor = getTaskExecutor();
if (executor != null) {
executor.execute(new Runnable() {
@Override
public void run() {
invokeListener(listener, event);
}
});
}
else {
invokeListener(listener, event);
}
}
}
protected void invokeListener(ApplicationListener listener, ApplicationEvent event) {
ErrorHandler errorHandler = getErrorHandler();
//是否处理异常
if (errorHandler != null) {
try {
doInvokeListener(listener, event);
}
catch (Throwable err) {
errorHandler.handleError(err);
}
}
else {
doInvokeListener(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;
}
}
}