SpringBoot bean解析之refresh方法（四）
作者：互联网
上一篇文章讲述AbstractApplicationContext类的invokeBeanFactoryPostProcessors方法，主要完成通过BeanDefinitionRegistryPostProcessor向容器内添加bean定义，以及调用BeanFactoryPostProcessor向容器内的bean添加属性。接下来，我们来看registerBeanPostProcessors(beanFactory)的代码；
/**
* Instantiate and register all BeanPostProcessor beans,
* respecting explicit order if given.
* <p>Must be called before any instantiation of application beans.
*/
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
此方法用于实例化并注册所有BeanPostProcessor bean。我们看静态方法registerBeanPostProcessors；
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
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);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
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);
// Now, register all regular BeanPostProcessors.
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);
// Finally, re-register all internal BeanPostProcessors.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
首先获得BeanPostProcessor的实现汇总到postProcessorNames，接下来，向beanFactory中添加一个BeanPostProcessor的实现，即：BeanPostProcessorChecker。
接下来遍历postProcessorNames，和上一篇文章分析的invokeBeanFactoryPostProcessors方法相似，这里首先判断当前实例是否实现了PriorityOrdered接口，如果实现了，将其bean实例添加到priorityOrderedPostProcessors集合中，并且如果它是MergedBeanDefinitionPostProcessor的实现类，也要添加到internalPostProcessors集合中否则，判断当前实例是否实现了Ordered接口，如果实现了，将其bean名字添加到orderedPostProcessorNames集合中；再否则，将其bean名字添加到nonOrderedPostProcessorNames集合当中。
接下来排序priorityOrderedPostProcessors集合的对象，并将集合中的对象注册到beanFactory；获取orderedPostProcessorNames集合中的bean名字对应的实例，添加到orderedPostProcessors集合，排序，注册（只注册，不不调用，因为bean已经实例化完成了）；获取nonOrderedPostProcessorNames集合中的bean名字对应的实例，添加到nonOrderedPostProcessors集合，排序，注册；如果上述步骤有MergedBeanDefinitionPostProcessor的实现，都会添加到集合internalPostProcessors中；再接下来对internalPostProcessors集合中的元素排序，注册；
最后，再向beanFactory添加一个BeanPostProcessor的实现，即：ApplicationListenerDetector，方法结束。
回到refresh()方法，看下一步的initMessageSource方法：
/**
* Initialize the MessageSource.
* Use parent's if none defined in this context.
*/
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 + "]");
}
}
}
这个方法初始化MessageSource，主要是国际化多语言的配置。这里本人使用的不多，在这里跳过。
继续看refresh方法的调用：initApplicationEventMulticaster：
/**
* Initialize the ApplicationEventMulticaster.
* Uses SimpleApplicationEventMulticaster if none defined in the context.
* @see org.springframework.context.event.SimpleApplicationEventMulticaster
*/
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() + "]");
}
}
}
这个方法初始化事件广播器，如果环境中没有事件广播器的实现，就使用一个SimpleApplicationEventMulticaster的实现。
继续看refresh方法后面的调用：onRefresh：
@Override
protected void onRefresh() {
super.onRefresh();
try {
createWebServer();
}
catch (Throwable ex) {
throw new ApplicationContextException("Unable to start web server", ex);
}
}
这里首先调用父类的onRefresh方法初始化"主题容器"，像我们这里调用的是ServletWebServerApplicationContext的onRefresh，用来初始化一个web环境。
继续看refresh方法的调用：registerListeners：
/**
* Add beans that implement ApplicationListener as listeners.
* Doesn't affect other listeners, which can be added without being beans.
*/
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 (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
这里在监听器的相关文章中有所体现，就不加赘述了，这里需要注意如果earlyApplicationEvents不为空，则在方法中广播这些事件。earlyApplicationEvents里面保存的是（由于listener未完成加载导致的）尚未处理的事件。
接下来，finishBeanFactoryInitialization方法初始化所有剩下的单例bean，后面的文章中会详细介绍这个方法，finishRefresh初始化、并调用生命周期处理器的onRefresh，发布ContextRefreshedEvent事件。
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标签：BeanPostProcessor,pp,SpringBoot,beanFactory,ppName,refresh,bean,new 来源： https://blog.csdn.net/lhf2112/article/details/104498735