本文章基于 Spring 5.3.15
Spring IOC 的核心是
AbstractApplicationContext的refresh方法。其中一共有 13 个主要方法，这里分析第 7 个：
initMessageSource。
1 AbstractApplicationContext
1-1 初始化 message 源
initMessageSource()
protected void initMessageSource() {
// 获取 Bean 工厂
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
// 如果在配置中已经配置了 messageSource，那么将 messageSource 提取并记录在 this.messageSource 中
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
if (hms.getParentMessageSource() == null) {
hms.setParentMessageSource(getInternalParentMessageSource());
}
}
if (logger.isTraceEnabled()) {
logger.trace("Using MessageSource [" + this.messageSource + "]");
}
} else {
// 如果用户并没有定义配置文件，那么使用临时的 DelegatingMessageSource 以便于作为调用 getMessage 方法的返回
DelegatingMessageSource dms = new DelegatingMessageSource();
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
// 注册单例
beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
if (logger.isTraceEnabled()) {
logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
}
}
}
1-2 获取 Bean 工厂
getBeanFactory()
2 AbstractRefreshableApplicationContext
public final ConfigurableListableBeanFactory getBeanFactory() {
DefaultListableBeanFactory beanFactory = this.beanFactory;
if (beanFactory == null) {
throw new IllegalStateException("BeanFactory not initialized or already closed - " + "call 'refresh' before accessing beans via the ApplicationContext");
}
return beanFactory;
}
if (beanFactory == null)由于 beanFactory 已经被赋值，直接返回。
1 AbstractApplicationContext
1-2 注册单例
registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource)
3 DefaultListableBeanFactory
public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
// 调用父类方法
super.registerSingleton(beanName, singletonObject);
// 手动更新单例名称
updateManualSingletonNames(set -> set.add(beanName), set -> !this.beanDefinitionMap.containsKey(beanName));
// 按类型清除缓存
clearByTypeCache();
}
3-1 调用父类方法
super.registerSingleton(beanName, singletonObject)
4 DefaultSingletonBeanRegistry
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");
}
// 添加单例
addSingleton(beanName, singletonObject);
}
}
4-1 添加单例
addSingleton(beanName, singletonObject)
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);
}
}
3 DefaultListableBeanFactory
3-1 手动更新单例名称
updateManualSingletonNames(set -> set.add(beanName), set -> !this.beanDefinitionMap.containsKey(beanName))
private void updateManualSingletonNames(Consumer<Set<String>> action, Predicate<Set<String>> condition) {
// 如果已开始创建 Bean
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
if (condition.test(this.manualSingletonNames)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
action.accept(updatedSingletons);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// Still in startup registration phase
if (condition.test(this.manualSingletonNames)) {
action.accept(this.manualSingletonNames);
}
}
}
3-2 判断是否已开始创建 Bean
private final Set<String> alreadyCreated = Collections.newSetFromMap(new ConcurrentHashMap<>(256));
protected boolean hasBeanCreationStarted() {
return !this.alreadyCreated.isEmpty();
}
3-1 按类型清除缓存
clearByTypeCache()
private void clearByTypeCache() {
this.allBeanNamesByType.clear();
this.singletonBeanNamesByType.clear();
}
