42、【死磕 Spring】—– 第四十二篇深入分析 ApplicationContext 的 refresh()
原文出自：http://cmsblogs.com
上篇博客只是对 ApplicationContext 相关的接口做了一个简单的介绍，作为一个高富帅级别的 Spring 容器，它涉及的方法实在是太多了，全部介绍是不可能的，而且大部分功能都已经在前面系列博客中做了详细的介绍，所以这篇博问介绍 ApplicationContext 最重要的方法（小编认为的） ：refresh()。
refresh() 是定义在 ConfigurableApplicationContext 类中的，如下：
/**
* Load or refresh the persistent representation of the configuration,
* which might an XML file, properties file, or relational database schema.
* As this is a startup method, it should destroy already created singletons
* if it fails, to avoid dangling resources. In other words, after invocation
* of that method, either all or no singletons at all should be instantiated.
* @throws BeansException if the bean factory could not be initialized
* @throws IllegalStateException if already initialized and multiple refresh
* attempts are not supported
*/
void refresh() throws BeansException, IllegalStateException;
作用就是：刷新 Spring 的应用上下文。其实现是在 AbstractApplicationContext 中实现。如下：
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 准备刷新上下文环境
prepareRefresh();
// 创建并初始化 BeanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 填充BeanFactory功能
prepareBeanFactory(beanFactory);
try {
// 提供子类覆盖的额外处理，即子类处理自定义的BeanFactoryPostProcess
postProcessBeanFactory(beanFactory);
// 激活各种BeanFactory处理器
invokeBeanFactoryPostProcessors(beanFactory);
// 注册拦截Bean创建的Bean处理器，即注册 BeanPostProcessor
registerBeanPostProcessors(beanFactory);
// 初始化上下文中的资源文件，如国际化文件的处理等
initMessageSource();
// 初始化上下文事件广播器
initApplicationEventMulticaster();
// 给子类扩展初始化其他Bean
onRefresh();
// 在所有bean中查找listener bean，然后注册到广播器中
registerListeners();
// 初始化剩下的单例Bean(非延迟加载的)
finishBeanFactoryInitialization(beanFactory);
// 完成刷新过程,通知生命周期处理器lifecycleProcessor刷新过程,同时发出ContextRefreshEvent通知别人
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// 销毁已经创建的Bean
destroyBeans();
// 重置容器激活标签
cancelRefresh(ex);
// 抛出异常
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
这里每一个方法都非常重要，需要一个一个地解释说明。
prepareRefresh()
初始化上下文环境，对系统的环境变量或者系统属性进行准备和校验,如环境变量中必须设置某个值才能运行，否则不能运行，这个时候可以在这里加这个校验，重写initPropertySources方法就好了
protected void prepareRefresh() {
// 设置启动日期
this.startupDate = System.currentTimeMillis();
// 设置 context 当前状态
this.closed.set(false);
this.active.set(true);
if (logger.isInfoEnabled()) {
logger.info("Refreshing " + this);
}
// 初始化context environment（上下文环境）中的占位符属性来源
initPropertySources();
// 对属性进行必要的验证
getEnvironment().validateRequiredProperties();
this.earlyApplicationEvents = new LinkedHashSet<>();
}
该方法主要是做一些准备工作，如：
- 设置 context 启动时间
- 设置 context 的当前状态
- 初始化 context environment 中占位符
- 对属性进行必要的验证
obtainFreshBeanFactory()
创建并初始化 BeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
// 刷新 BeanFactory
refreshBeanFactory();
// 获取 BeanFactory
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
核心方法就在 refreshBeanFactory() ，该方法的核心任务就是创建 BeanFactory 并对其就行一番初始化。如下：
protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
- 判断当前容器是否存在一个 BeanFactory，如果存在则对其进行销毁和关闭
- 调用
createBeanFactory()创建一个 BeanFactory 实例，其实就是 DefaultListableBeanFactory - 自定义 BeanFactory
- 加载 BeanDefinition
- 将创建好的 bean 工厂的引用交给的 context 来管理
上面 5 个步骤，都是比较简单的，但是有必要讲解下第 4 步：加载 BeanDefinition。如果各位看过 【死磕 Spring】系列的话，在刚刚开始分析源码的时候，小编就是以 loadBeanDefinitions() 为入口来分析的，如下：
ClassPathResource resource = new ClassPathResource("bean.xml");
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
reader.loadBeanDefinitions(resource);
只不过这段代码的 loadBeanDefinitions() 是定义在 BeanDefinitionReader 中，而此处的 loadBeanDefinitions() 则是定义在 AbstractRefreshableApplicationContext 中，如下：
protected abstract void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)
throws BeansException, IOException
由具体的子类实现，我们以 AbstractXmlApplicationContext 为例，实现如下：
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
initBeanDefinitionReader(beanDefinitionReader);
loadBeanDefinitions(beanDefinitionReader);
}
新建 XmlBeanDefinitionReader 实例对象 beanDefinitionReader，调用 initBeanDefinitionReader() 对其进行初始化，然后调用 loadBeanDefinitions() 加载 BeanDefinition。
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}
到这里我们发现，其实内部依然是调用 BeanDefinitionReader#loadBeanDefinitionn() 进行 BeanDefinition 的加载进程。
prepareBeanFactory(beanFactory)
填充 BeanFactory 功能
上面获取获取的 BeanFactory 除了加载了一些 BeanDefinition 就没有其他任何东西了，这个时候其实还不能投入生产，因为还少配置了一些东西，比如 context的 ClassLoader 和 后置处理器等等。
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// 设置beanFactory的classLoader
beanFactory.setBeanClassLoader(getClassLoader());
// 设置beanFactory的表达式语言处理器,Spring3开始增加了对语言表达式的支持,默认可以使用#{bean.xxx}的形式来调用相关属性值
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
// 为beanFactory增加一个默认的propertyEditor
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// 添加ApplicationContextAwareProcessor
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
// 设置忽略自动装配的接口
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// 设置几个自动装配的特殊规则
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// Register early post-processor for detecting inner beans as ApplicationListeners.
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// 增加对AspectJ的支持
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// 注册默认的系统环境bean
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
看上面的源码知道这个就是对 BeanFactory 设置各种各种的功能。
postProcessBeanFactory()
提供子类覆盖的额外处理，即子类处理自定义的BeanFactoryPostProcess
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
beanFactory.ignoreDependencyInterface(ServletConfigAware.class);
WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
}
- 添加 ServletContextAwareProcessor 到 BeanFactory 容器中，该 processor 实现 BeanPostProcessor 接口，主要用于将ServletContext 传递给实现了 ServletContextAware 接口的 bean
- 忽略 ServletContextAware、ServletConfigAware
- 注册 WEB 应用特定的域（scope）到 beanFactory 中，以便 WebApplicationContext 可以使用它们。比如 "request" , "session" , "globalSession" , "application"
- 注册 WEB 应用特定的 Environment bean 到 beanFactory 中，以便WebApplicationContext 可以使用它们。如："contextParameters", "contextAttributes"
invokeBeanFactoryPostProcessors()
激活各种BeanFactory处理器
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// 定义一个 set 保存所有的 BeanFactoryPostProcessors
Set<String> processedBeans = new HashSet<>();
// 如果当前 BeanFactory 为 BeanDefinitionRegistry
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// BeanFactoryPostProcessor 集合
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
// BeanDefinitionRegistryPostProcessor 集合
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
// 迭代注册的 beanFactoryPostProcessors
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
// 如果是 BeanDefinitionRegistryPostProcessor，则调用 postProcessBeanDefinitionRegistry 进行注册，
// 同时加入到 registryProcessors 集合中
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
// 否则当做普通的 BeanFactoryPostProcessor 处理
// 添加到 regularPostProcessors 集合中即可，便于后面做后续处理
regularPostProcessors.add(postProcessor);
}
}
// 用于保存当前处理的 BeanDefinitionRegistryPostProcessor
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// 首先处理实现了 PriorityOrdered (有限排序接口)的 BeanDefinitionRegistryPostProcessor
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
// 排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
// 加入registryProcessors集合
registryProcessors.addAll(currentRegistryProcessors);
// 调用所有实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessors 的 postProcessBeanDefinitionRegistry()
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
// 清空，以备下次使用
currentRegistryProcessors.clear();
// 其次，调用是实现了 Ordered（普通排序接口）的 BeanDefinitionRegistryPostProcessors
// 逻辑和 上面一样
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// 最后调用其他的 BeanDefinitionRegistryPostProcessors
boolean reiterate = true;
while (reiterate) {
reiterate = false;
// 获取 BeanDefinitionRegistryPostProcessor
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 没有包含在 processedBeans 中的（因为包含了的都已经处理了）
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
// 与上面处理逻辑一致
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// 调用所有 BeanDefinitionRegistryPostProcessor (包括手动注册和通过配置文件注册)
// 和 BeanFactoryPostProcessor(只有手动注册)的回调函数(postProcessBeanFactory())
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// 如果不是 BeanDefinitionRegistry 只需要调用其回调函数（postProcessBeanFactory()）即可
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
//
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// 这里同样需要区分 PriorityOrdered 、Ordered 和 no Ordered
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
// 已经处理过了的，跳过
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
// PriorityOrdered
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
// Ordered
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
// no Ordered
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, PriorityOrdered 接口
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, Ordered 接口
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, no ordered
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}
上述代码较长，但是处理逻辑较为单一，就是对所有的 BeanDefinitionRegistryPostProcessors 、手动注册的 BeanFactoryPostProcessor 以及通过配置文件方式的 BeanFactoryPostProcessor 按照 PriorityOrdered 、 Ordered、no ordered 三种方式分开处理、调用。
registerBeanPostProcessors
注册拦截Bean创建的Bean处理器，即注册 BeanPostProcessor
与 BeanFactoryPostProcessor 一样，也是委托给 PostProcessorRegistrationDelegate 来实现的。
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 所有的 BeanPostProcessors
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// 注册 BeanPostProcessorChecker
// 主要用于记录一些 bean 的信息，这些 bean 不符合所有 BeanPostProcessors 处理的资格时
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// 区分 PriorityOrdered、Ordered 、 no ordered
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
// MergedBeanDefinition
List<BeanPostProcessor> internalPostProcessors = 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, PriorityOrdered
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, Ordered
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
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);
// onOrdered
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
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, all internal BeanPostProcessors.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// 重新注册用来自动探测内部ApplicationListener的post-processor，这样可以将他们移到处理器链条的末尾
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
initMessageSource
初始化上下文中的资源文件，如国际化文件的处理等
其实该方法就是初始化一个 MessageSource 接口的实现类，主要用于国际化/i18n。
protected void initMessageSource() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 包含 “messageSource” bean
if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
// 如果有父类
// HierarchicalMessageSource 分级处理的 MessageSource
if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
if (hms.getParentMessageSource() == null) {
// 如果没有注册父 MessageSource，则设置为父类上下文的的 MessageSource
hms.setParentMessageSource(getInternalParentMessageSource());
}
}
if (logger.isDebugEnabled()) {
logger.debug("Using MessageSource [" + this.messageSource + "]");
}
}
else {
// 使用 空 MessageSource
DelegatingMessageSource dms = new DelegatingMessageSource();
dms.setParentMessageSource(getInternalParentMessageSource());
this.messageSource = dms;
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 + "]");
}
}
}
initApplicationEventMulticaster
初始化上下文事件广播器
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 如果存在 applicationEventMulticaster bean，则获取赋值
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 {
// 没有则新建 SimpleApplicationEventMulticaster，并完成 bean 的注册
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 + "]");
}
}
}
如果当前容器中存在 applicationEventMulticaster 的 bean，则对 applicationEventMulticaster 赋值，否则新建一个 SimpleApplicationEventMulticaster 的对象（默认的），并完成注册。
onRefresh
给子类扩展初始化其他Bean
预留给 AbstractApplicationContext 的子类用于初始化其他特殊的 bean，该方法需要在所有单例 bean 初始化之前调用。
registerListeners
在所有 bean 中查找 listener bean，然后注册到广播器中
protected void registerListeners() {
// 注册静态 监听器
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// 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);
}
}
}
finishBeanFactoryInitialization
初始化剩下的单例Bean(非延迟加载的)
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// 初始化转换器
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));
}
// 如果之前没有注册 bean 后置处理器（例如PropertyPlaceholderConfigurer），则注册默认的解析器
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// 初始化 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);
}
// 停止使用临时的 ClassLoader
beanFactory.setTempClassLoader(null);
//
beanFactory.freezeConfiguration();
// 初始化所有剩余的单例（非延迟初始化）
beanFactory.preInstantiateSingletons();
}
finishRefresh
完成刷新过程,通知生命周期处理器 lifecycleProcessor 刷新过程,同时发出 ContextRefreshEvent 通知别人
主要是调用 LifecycleProcessor#onRefresh() ，并且发布事件（ContextRefreshedEvent）。
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
clearResourceCaches();
// 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);
}
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标题：42、【死磕 Spring】—– 第四十二篇深入分析 ApplicationContext 的 refresh()
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