Spring IOC容器核心流程源码分析 _IOC容器

犀渠玉剑良家子，白马金羁侠少年。这篇文章主要讲述Spring IOC容器核心流程源码分析相关的知识，希望能为你提供帮助。
@TOC
简单介绍Spring IOC的核心方法就在于refresh方法，这个方法里面完成了Spring的初始化、准备bean、实例化bean和扩展功能的实现。

这个方法的作用是什么？
它是如何完成这些功能的？
为什么要这样去实现？
有哪些值得借鉴的地方？

refresh方法在ConfigurableApplicationContext里面定义了这个方法：

/** * Load or refresh the persistent representation of the configuration, which * might be from java-based configuration, an XML file, a properties file, a * relational database schema, or some other format. * < p> 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 this 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;

根据注释可以知道，这个方法是用来加载刷新配置，这些配置可能来自java配置、xml文件、properties文件、关系型数据库或者其他格式。
作为一个启动方法，它应当在初始化失败后销毁已经创建的单例，防止占着资源而不使用。也就是说调用这个方法的话，要么所有的单例已经被实例化，要么所有的单例都不存在。
BeansException：bean工厂不能被初始化，抛出BeansException
IllegalStateException：bean工厂已经被初始化了，但是不支持多次刷新，抛出IllegalStateException
具体实现在AbstractApplicationContext中进行了实现：

@Override public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { //为刷新做准备，初始化各种状态，启动时间、关闭激活状态、配置文件信息等 prepareRefresh(); //通知子类刷新内部BeanFactory，并返回刷新后的BeanFactory //关注方法中的refreshBeanFactory方法，两个子类对它重写的差异 //AbstractRefreshableApplicationContext#refreshBeanFactory中重新构建，完成BeanDefinition的解析构建 //GenericApplicationContext#refreshBeanFactory则是设置ID，并且只能刷新一次 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); //给容器准备BeanFactory，配置相关的属性 prepareBeanFactory(beanFactory); try { //允许子类处理后置beanFactory postProcessBeanFactory(beanFactory); //调用注册了beanFactory后置处理器接口实例bean对应的方法 invokeBeanFactoryPostProcessors(beanFactory); //注册bean后置处理器接口的实例bean registerBeanPostProcessors(beanFactory); //初始化国际化资源 initMessageSource(); //初始化事件传播者 initApplicationEventMulticaster(); //refresh事件，初始化一些指定的bean onRefresh(); //注册监听器bean registerListeners(); //完成bean工厂的初始化，初始化所有非懒加载的单例bean finishBeanFactoryInitialization(beanFactory); //最后，发布finishRefresh事件 finishRefresh(); }catch (BeansException ex) { if (logger.isWarnEnabled()) { logger.warn("Exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); }//销毁了所有已经创建了的单例bean destroyBeans(); //重置active标记 cancelRefresh(ex); // Propagate exception to caller. throw ex; }finally { // Reset common introspection caches in Spring\'s core, since we // might not ever need metadata for singleton beans anymore... resetCommonCaches(); } } }

使用示例：

GenericApplicationContext context3 = new GenericApplicationContext(); new XmlBeanDefinitionReader(context3).loadBeanDefinitions("classpath:application.xml"); new ClassPathBeanDefinitionScanner(context3).scan("edu.demo"); // 一定要刷新 context3.refresh();

IOC容器刷新整体流程 prepareRefresh方法

//关闭和刷新的状态都是AtomicBoolean类型的，原子性 /** Flag that indicates whether this context is currently active. */ private final AtomicBoolean active = new AtomicBoolean(); /** Flag that indicates whether this context has been closed already. */ private final AtomicBoolean closed = new AtomicBoolean(); /** * 为容器刷新做准备，设置启动日期和活动标识 * 并执行一些资源的初始化 */ protected void prepareRefresh() { //容器切换到启动状态 //设置启动容器的时间 this.startupDate = System.currentTimeMillis(); //设置关闭的状态 this.closed.set(false); //设置启动的状态 this.active.set(true); if (logger.isDebugEnabled()) { if (logger.isTraceEnabled()) { logger.trace("Refreshing " + this); } else { logger.debug("Refreshing " + getDisplayName()); } }//初始化容器的占位符资源 initPropertySources(); // 验证所有标记为required的属性都是可解析的: // see ConfigurablePropertyResolver#setRequiredProperties getEnvironment().validateRequiredProperties(); //一些监听器的初始化 // Store pre-refresh ApplicationListeners... if (this.earlyApplicationListeners == null) { this.earlyApplicationListeners = new LinkedHashSet< > (this.applicationListeners); } else { // Reset local application listeners to pre-refresh state. this.applicationListeners.clear(); this.applicationListeners.addAll(this.earlyApplicationListeners); }// Allow for the collection of early ApplicationEvents, // to be published once the multicaster is available... this.earlyApplicationEvents = new LinkedHashSet< > (); }

obtainFreshBeanFactory方法

/** * 告诉子类刷新内部的bean factory. * @return the fresh BeanFactory instance * @see #refreshBeanFactory() * @see #getBeanFactory() */ protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { refreshBeanFactory(); return getBeanFactory(); }

其实就是配置用户的属性、加载bean定义，并且返回刷新后的bean工厂。prepareBeanFacotry方法内部又有两个抽象方法构成，交给子类去实现。也就是说子类必定含有一个BeanFactory实例，并且还需要提供刷新方法，返回BeanFactory实例的方法。
具体实现类：

AbstractRefreshableApplicationContext

AbstractRefreshableApplicationContext中实现的刷新方法，可以被多次的调用执行，也就是可以多次刷新。

/** * 实际的刷新方法。关闭以前的bean工厂，初始化一个新的bean工厂 */ @Override protected final void refreshBeanFactory() throws BeansException { //如果存在bean工厂，则销毁单例bean，关闭bean工厂 if (hasBeanFactory()) { destroyBeans(); closeBeanFactory(); } try { //创建DefaultListableBeanFactory实例 DefaultListableBeanFactory beanFactory = createBeanFactory(); //设置ID beanFactory.setSerializationId(getId()); //自定义bean工厂属性，bean定义重新、循环引用等配置 customizeBeanFactory(beanFactory); //等待子类实现的，向bean工厂注册bean定义 loadBeanDefinitions(beanFactory); //持有bean工厂的实例，以便在getBeanFactory方法中返回出去 this.beanFactory = beanFactory; } catch (IOException ex) { throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex); } }//自定义bean工厂属性 protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) { if (this.allowBeanDefinitionOverriding != null) { beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding); } if (this.allowCircularReferences != null) { beanFactory.setAllowCircularReferences(this.allowCircularReferences); } }//关闭bean工厂的方法 @Override protected final void closeBeanFactory() { DefaultListableBeanFactory beanFactory = this.beanFactory; //如果bean工厂存在 if (beanFactory != null) { //设置ID为空 beanFactory.setSerializationId(null); //设置bean工厂的实例为空 this.beanFactory = null; } }

AbstractApplicationContext类中的销毁方法：

//销毁方法 protected void destroyBeans() { getBeanFactory().destroySingletons(); }

GenericApplicationContext

GenericApplicationContext中的刷新方法，只能被调用一次，被AtomicBoolean类型的refreshed控制着

private final AtomicBoolean refreshed = new AtomicBoolean(); /** * 持有一个内部的bean工厂，通过公共的方法注册bean * @see #registerBeanDefinition */ @Override protected final void refreshBeanFactory() throws IllegalStateException { //CAS的方式进行修改 //多次刷新就抛出异常 if (!this.refreshed.compareAndSet(false, true)) { throw new IllegalStateException( "GenericApplicationContext does not support multiple refresh attempts: just call \'refresh\' once"); } //设置ID this.beanFactory.setSerializationId(getId()); }

beanFactory在构造函数中被创建的，代码如下：

/** * Create a new GenericApplicationContext. * @see #registerBeanDefinition * @see #refresh */ public GenericApplicationContext() { this.beanFactory = new DefaultListableBeanFactory(); }/** * Create a new GenericApplicationContext with the given DefaultListableBeanFactory. * @param beanFactory the DefaultListableBeanFactory instance to use for this context * @see #registerBeanDefinition * @see #refresh */ public GenericApplicationContext(DefaultListableBeanFactory beanFactory) { Assert.notNull(beanFactory, "BeanFactory must not be null"); this.beanFactory = beanFactory; }

这个时候的beanFactory里面都有些什么呢？根据之前的注解的加载过程。可以知道，应该有BeanFactoryPostProcessor、BeanPostProcessor、ApplicationListener信息。
prepareBeanFactory方法

/** * 配置工厂的标准容器特征 * 例如容器的ClassLoader和post-processor * @param beanFactory the BeanFactory to configure */ protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) { // Tell the internal bean factory to use the context\'s class loader etc. //给bean工作准备ClassLoader、SPL表达式解析器、属性编辑注册器等 beanFactory.setBeanClassLoader(getClassLoader()); beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader())); beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment())); // Configure the bean factory with context callbacks. //向beanFactory注册ApplicationContextAwareProcessor //后面的六种Aware忽略他们的自动依赖注入 beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this)); beanFactory.ignoreDependencyInterface(EnvironmentAware.class); beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class); beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class); beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class); beanFactory.ignoreDependencyInterface(MessageSourceAware.class); beanFactory.ignoreDependencyInterface(ApplicationContextAware.class); // BeanFactory interface not registered as resolvable type in a plain factory. // MessageSource registered (and found for autowiring) as a bean. //依赖需要使用的bean，IOC容器自己的多角色身份，@Autowried方式获得下列类型bean 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. //注入ApplicationListeners接口实现的发现处理器，同时带有销毁、bean定义混合的实现 beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this)); // Detect a LoadTimeWeaver and prepare for weaving, if found. 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())); }// Register default environment beans. if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) { beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment()); } if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) { // properties配置文件 beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties()); } if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) { // 操作系统环境变量：JAVA_HOME等 beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment()); } }

ApplicationContextAwareProcessor方法中的，注入Processor

@Override @Nullable public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { //只针对EnvironmentAware、EmbeddedValueResolverAware、ResourceLoaderAware、ApplicationEventPublisherAware、MessageSourceAware、ApplicationContextAware 6种实现进行处理。 if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware || bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware || bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)){ return bean; }AccessControlContext acc = null; if (System.getSecurityManager() != null) { acc = this.applicationContext.getBeanFactory().getAccessControlContext(); }if (acc != null) { AccessController.doPrivileged((PrivilegedAction< Object> ) () -> { invokeAwareInterfaces(bean); return null; }, acc); } else { invokeAwareInterfaces(bean); }return bean; }//将beanFactory注入给上述的6种Aware private void invokeAwareInterfaces(Object bean) { if (bean instanceof EnvironmentAware) { ((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment()); } if (bean instanceof EmbeddedValueResolverAware) { ((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver); } if (bean instanceof ResourceLoaderAware) { ((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext); } if (bean instanceof ApplicationEventPublisherAware) { ((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext); } if (bean instanceof MessageSourceAware) { ((MessageSourceAware) bean).setMessageSource(this.applicationContext); } if (bean instanceof ApplicationContextAware) { ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext); } }

postProcessBeanFactory方法postProcessBeanFactory方法并没有去实现它。

/** * Modify the application context\'s internal bean factory after its standard * initialization. All bean definitions will have been loaded, but no beans * will have been instantiated yet. This allows for registering special * BeanPostProcessors etc in certain ApplicationContext implementations. * @param beanFactory the bean factory used by the application context */ protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) { }

invokeBeanFactoryPostProcessors方法这个时候，bean工厂基本上已经准备完成，但是bean实例还没有进行初始化，接下来调用BeanFactoryPostProcessor对Bean工厂中的Bean定义进行调整

/** * 执行BeanFactoryPostProcessor * < p> 必须在单例bean实例化之前调用 */ protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { //最重要的处理在委托里面实现 //getBeanFactoryPostProcessors()获取的是容器里面的列表属性， //这个属性没有机会给外部去注入BeanFactoryPostProcessor对象。 //因为ApplicationContext子类在构造函数中调用了refresh方法。所以这里是个空值 PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors()); // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor) if (beanFactory.getTempClassLoader() == null & & beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader())); } }

invokeBeanFactoryPostProcessors方法：

public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List< BeanFactoryPostProcessor> beanFactoryPostProcessors) {// Invoke BeanDefinitionRegistryPostProcessors first, if any. Set< String> processedBeans = new HashSet< > (); if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; //BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor List< BeanFactoryPostProcessor> regularPostProcessors = new ArrayList< > (); List< BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList< > (); for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { //获取BeanDefinitionRegistryPostProcessor BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; //这里既然做了处理，为何又加入到了registryProcessors集合中？ registryProcessor.postProcessBeanDefinitionRegistry(registry); registryProcessors.add(registryProcessor); } else { regularPostProcessors.add(postProcessor); } }// Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! // Separate between BeanDefinitionRegistryPostProcessors that implement // PriorityOrdered, Ordered, and the rest. List< BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList< > (); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. //第一步，处理继承PriorityOrdered的BeanDefinitionRegistryPostProcessors 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); } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered. //第二步，处理继承自Ordered的BeanDefinitionRegistryPostProcessors 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(); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear. //最后一步，处理没有优先顺序的BeanDefinitionRegistryPostProcessors boolean reiterate = true; while (reiterate) { reiterate = false; postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); reiterate = true; } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); }// Now, invoke the postProcessBeanFactory callback of all processors handled so far. //回调 invokeBeanFactoryPostProcessors(registryProcessors, beanFactory); invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); }else { // Invoke factory processors registered with the context instance. invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory); }// Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, // Ordered, and the rest. //处理BeanFactoryPostProcessor，按照PriorityOrdered、Ordered和其他 List< BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList< > (); List< String> orderedPostProcessorNames = new ArrayList< > (); List< String> nonOrderedPostProcessorNames = new ArrayList< > (); for (String ppName : postProcessorNames) { if (processedBeans.contains(ppName)) { // skip - already processed in first phase above } else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class)); } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessorNames.add(ppName); } else { nonOrderedPostProcessorNames.add(ppName); } }// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered. //第一步，处理继承自PriorityOrdered的BeanFactoryPostProcessors sortPostProcessors(priorityOrderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // Next, invoke the BeanFactoryPostProcessors that implement Ordered. //第二步，处理继承自Ordered的BeanFactoryPostProcessors List< BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList< > (orderedPostProcessorNames.size()); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // Finally, invoke all other BeanFactoryPostProcessors. //最后一步，处理其他的BeanFactoryPostProcessors List< BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList< > (nonOrderedPostProcessorNames.size()); 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... //清除缓存，因为后面的处理器可能会修改元数据 beanFactory.clearMetadataCache(); }

从上面的源码部分可以看到：

拆成了两部分：registryProcessors、regularPostProcessors，分别处理BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor
排序处理：PriorityOrdered、Ordered和为排序的，按照这样的优先级进行处理

多次调用了invokeBeanFactoryPostProcessors，因为在调用BeanFactoryPostProcessors的过程中，还会继续产生BeanFactoryPostProcessors，这里多次调用，就是为了处理掉所有的BeanFactoryPostProcessors。
registerBeanPostProcessors方法到了这一步，bean定义已经加载完成，bean工厂完成了刷新和实例化，而且通过BeanFactoryProcessor修整了bean定义信息，接下来注册BeanPostProcessors

/** * 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); }

PostProcessorRegistrationDelegate的registerBeanPostProcessors方法：

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)); }

可以看到上面的源码部分，和与BeanFactroyPostProcessor的处理简直一样，排序然后调用处理逻辑。

priorityOrderedPostProcessors
orderedPostProcessors
nonOrderedPostProcessors
internalPostProcessors
ApplicationListenerDetector

下面是排序的实例：

没有继承任何排序的接口：

@Component public class MyBeanDefinitonRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {@Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { System.out.println("--- MyBeanDefinitonRegistryPostProcessor.postProcessBeanFactory 被执行了。"); }@Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { System.out.println("--- MyBeanDefinitonRegistryPostProcessor.postProcessBeanDefinitionRegistry 被执行了。"); }

}

- 继承Ordered接口： ```java @Component public class MyBeanDefinitonRegistryPostProcessor2 implements BeanDefinitionRegistryPostProcessor, Ordered {@Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { System.out.println("--- MyBeanDefinitonRegistryPostProcessor2.postProcessBeanFactory 被执行了。"); }@Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { System.out.println("--- MyBeanDefinitonRegistryPostProcessor2.postProcessBeanDefinitionRegistry 被执行了。"); }@Override public int getOrder() { return 0; } }

继承PriorityOrdered接口：

@Component public class MyBeanDefinitonRegistryPostProcessor3 implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {@Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { System.out.println("--- MyBeanDefinitonRegistryPostProcessor3.postProcessBeanFactory 被执行了。"); }@Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { System.out.println("--- MyBeanDefinitonRegistryPostProcessor3.postProcessBeanDefinitionRegistry 被执行了。"); }@Override public int getOrder() { return 1; } }

执行结果如下：

文章图片

从上图可以清楚的看到，PriorityOrdered > Ordered > 未排序
initMessageSource方法此时BenPostProcessor都已经注册完成，下一步就是准备国际化资源：

/** * 初始化国际化资源，如果没有，就使用父类的 */ protected void initMessageSource() { //获取bean工厂 ConfigurableListableBeanFactory beanFactory = getBeanFactory(); //如果Bean工厂中存在名为messageSource的bean，则使用它 if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) { this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class); // Make MessageSource aware of parent MessageSource. //获取父类的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. //使用DelegatingMessageSource作为国际化资源处理bean 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 + "]"); } } }

简单的例子：
在application.properties配置如下信息：

logging.config=classpath:logback.xml my.love=java

@Configuration @PropertySource("classpath:/application.properties") public class MessageConfiguration {@Bean("messageSource") public ReloadableResourceBundleMessageSource getReloadableResourceBundleMessageSource() { ReloadableResourceBundleMessageSource rms = new ReloadableResourceBundleMessageSource(); rms.setBasename("message"); return rms; } }

@MyComponetAnno public class MessageBean {@Autowired private ApplicationContext applicationContext; public MessageBean() { System.out.println("-----------------Abean 被实例化了。。。。。。。。。"); }public void doSomething() { System.out.println(this + " do something .....my.love=" + this.applicationContext.getEnvironment().getProperty("my.love")); System.out .println("-----------project.name=" + this.applicationContext.getMessage("project.name", null, Locale.CHINA)); } }

public class MessageStarter {public static void main(String[] args) { // 注解方式，指定扫描的包 AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext( "edu.demo.spring.message"); MessageBean bean = context.getBean(MessageBean.class); bean.doSomething(); context.close(); } }

输出如下：

文章图片

initApplicationEventMulticaster方法下面就是初始化事件多播器：

/** * 初始化ApplicationEventMulticaster. * Uses SimpleApplicationEventMulticaster if none defined in the context. * @see org.springframework.context.event.SimpleApplicationEventMulticaster */ protected void initApplicationEventMulticaster() { //获取bean工厂 ConfigurableListableBeanFactory beanFactory = getBeanFactory(); //如果bean工厂中包含applicationEventMulticaster，就使用它 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 { //使用SimpleApplicationEventMulticaster 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() + "]"); } } }

onRefresh方法没有子类进行实现

/** * Template method which can be overridden to add context-specific refresh work. * Called on initialization of special beans, before instantiation of singletons. * < p> This implementation is empty. * @throws BeansException in case of errors * @see #refresh() */ protected void onRefresh() throws BeansException { // For subclasses: do nothing by default. }

registerListeners方法接下来，检查事件监听器，并注册到事件传播器上

/** *在不生成Bean对象的情况下添加ApplicationListener bean作为监听器 * 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 (!CollectionUtils.isEmpty(earlyEventsToProcess)) { for (ApplicationEvent earlyEvent : earlyEventsToProcess) { getApplicationEventMulticaster().multicastEvent(earlyEvent); } } }

事件广播器执行的方法：
SimpleApplicationEventMulticaster的multicastEvent(ApplicationEvent, ResolvableType)方法：

@Override public void multicastEvent(ApplicationEvent event) { multicastEvent(event, resolveDefaultEventType(event)); }@Override public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) { ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event)); Executor executor = getTaskExecutor(); for (ApplicationListener< ?> listener : getApplicationListeners(event, type)) { if (executor != null) { executor.execute(() -> invokeListener(listener, event)); } else { invokeListener(listener, event); } } }

finishBeanFactoryInitialization方法完成bean工厂的初始化，将bean工厂中，非懒加载的单例bean进行实例化
这一部分将在后面的文章中进行分析

/** * Finish the initialization of this context\'s bean factory, * initializing all remaining singleton beans. */ protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) { // Initialize conversion service for this context. 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)); }// Register a default embedded value resolver if no bean post-processor // (such as a PropertyPlaceholderConfigurer bean) registered any before: // at this point, primarily for resolution in annotation attribute values. if (!beanFactory.hasEmbeddedValueResolver()) { beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal)); }// 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); }// Stop using the temporary ClassLoader for type matching. beanFactory.setTempClassLoader(null); // Allow for caching all bean definition metadata, not expecting further changes. beanFactory.freezeConfiguration(); // Instantiate all remaining (non-lazy-init) singletons. beanFactory.preInstantiateSingletons(); }

finishRefresh方法

/** * Finish the refresh of this context, invoking the LifecycleProcessor\'s * onRefresh() method and publishing the * {@link org.springframework.context.event.ContextRefreshedEvent}. */ protected void finishRefresh() { // Clear context-level resource caches (such as ASM metadata from scanning). //清除缓存 clearResourceCaches(); // Initialize lifecycle processor for this context. //初始化容器的生命周期处理器 initLifecycleProcessor(); // Propagate refresh to lifecycle processor first. //将刷新传播到生命周期处理器 getLifecycleProcessor().onRefresh(); // Publish the final event. //发布最终事件 publishEvent(new ContextRefreshedEvent(this)); // Participate in LiveBeansView MBean, if active. LiveBeansView.registerApplicationContext(this); }

容器的关闭：
AbstractApplicationContext#close
AbstractApplicationContext#registerShutdownHook
AbstractApplicationContext#doClose
【Spring IOC容器核心流程源码分析】整体流程图如下：