上一篇：12-Spring源码解析之refresh(5)——registerBeanPostProcessors
上一篇我们分析完了registerBeanPostProcessors，接下来，我们开始分析refresh中的第七个方法initMessageSource和第八个方法initApplicationEventMulticaster
一、initMessageSource
初始化MessageSource组件（做消息绑定、消息解析）
protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 判断是否已经存在名为messageSource的Bean了
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();
// 获取父容器的messageSource字段
// 一般都为空
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
// ----------该方法的核心---------------
// 把MessageSource注入到容器中，以后获取国际化配置文件值的时候，可以自动注入MessageSource
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isTraceEnabled()) {
logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
}
}
}
// 取出国际化配置文件中的某个key值(可以按住区域信息获取)
protected MessageSource getInternalParentMessageSource() {
return (getParent() instanceof AbstractApplicationContext ?
((AbstractApplicationContext) getParent()).messageSource : getParent());
}
1.1 registerSingleton
public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
super.registerSingleton(beanName, singletonObject);
updateManualSingletonNames(set -> set.add(beanName), set -> !this.beanDefinitionMap.containsKey(beanName));
clearByTypeCache();
}
首先要调用父类的registerSingleton
public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
Assert.notNull(beanName, "Bean name must not be null");
Assert.notNull(singletonObject, "Singleton object must not be null");
synchronized (this.singletonObjects) {
Object oldObject = this.singletonObjects.get(beanName);
if (oldObject != null) {
throw new IllegalStateException("Could not register object [" + singletonObject +
"] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
}
addSingleton(beanName, singletonObject);
}
}
将beanName和singletonObject添加到singletonObjects和registeredSingletons中，并将其从singletonFactories和earlySingletonObjects中移除。这里面涉及了用于存储Bean的4种不同的Map。这里需要简单的解释一下。这些在创建Bean的时候会经常用到，用于解决循环依赖，缓存等问题。
singletonObjects：用于保存beanName和bean实例之间的关系singletonFactories：用于保存beanName和创建bean工厂之间的关系earlySingletonObjects：用于保存beanName和bean实例之间的关系，与singletonObjects不同之处在于：当一个单利bean被放到这里面之后，那么当bean还在创建过程种，就可以通过getBean方法获取到了，目的是用来检查循环依赖。registeredSingletons：用于保存当前所有已经创建的bean。
protected void addSingleton(String beanName, Object singletonObject) {
synchronized (this.singletonObjects) {
this.singletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
this.earlySingletonObjects.remove(beanName);
this.registeredSingletons.add(beanName);
}
}
在initMessageSource执行完后，我们看一下beanFactory的registeredSingletons的属性的值
-
registeredSingletons[0]–registeredSingletons[2]- 在
refresh->prepareBeanFactory方法中注册
- 在
-
registeredSingletons[3]–registeredSingletons[6]- 在
refresh->invokeBeanFactoryPostProcessors方法中注册
- 在
-
registeredSingletons[7]–registeredSingletons[10]- 在
refresh->registerBeanPostProcessors方法中注册
- 在
-
registeredSingletons[11]- 在
refresh->initMessageSource方法中注册
- 在
二、initApplicationEventMulticaster 事件派发器
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() + "]");
}
}
}
跟initMessageSource方法类似，这里不详细介绍了。看一下执行完该方法后beanFactory的registeredSingletons的属性的值
beanFactory的registeredSingletons的属性中多了applicationEventMulticaster。
下一篇文章我们讲解refresh的第九个方法onRefresh和第十个方法registerListeners。
