本文主要是介绍Spring框架十、Spring IOC启动流程源码分析二，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
紧接着上一篇分析
一、prepareBeanFactory(beanFactory)
prepareBeanFactory()这个方法主要做beanFactory的预准备工作，对beanfactory配置容器特性，例如类加载器、事件处理器等
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {// Tell the internal bean factory to use the context's class loader etc.//设置beanfactory的classloader为当前context的classloaderbeanFactory.setBeanClassLoader(getClassLoader());//设置beanfactory的表达式语言处理器beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));//为beanfactory增加一个默认的propertyEditor，这个主要是对bean的属性等设置管理的一个工具beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));// Configure the bean factory with context callbacks.//添加beanpostProcessorbeanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));//设置忽略的自动装配的接口beanFactory.ignoreDependencyInterface(EnvironmentAware.class);beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);beanFactory.ignoreDependencyInterface(MessageSourceAware.class);beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);// BeanFactory interface not registered as resolvable type in a plain factory.// MessageSource registered (and found for autowiring) as a bean.//设置可以解析的自动装配，能在任何组件中自动注入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.//添加后置处理器beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));// Detect a LoadTimeWeaver and prepare for weaving, if found.//添加对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()));}// Register default environment beans.//给BeanFactory中注册一些能用的组件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());}}
二、postProcessBeanFactory(beanFactory)
Spring的一个扩展点
beanFactory准备工作完成之后要进行的后置处理工作，留给子类扩展使用，如果有Bean实现了BeanFactoryPostProcessor接口，那么在容器初始化以后，Spring 会负责调用里面的 postProcessBeanFactory 方法。具体的子类可以在这步的时候添加一些特殊的 BeanFactoryPostProcessor 的实现类或做点什么事。
所以是一个空方法：
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {}
三、invokeBeanFactoryPostProcessors(beanFactory)
此方法执行BeanFactory的后置处理器，在BeanFactory标准初始化之后执行的，调用所有注册的BeanFactoryPostProcessor的Bean
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {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()));}}
四、registerBeanPostProcessors(beanFactory)
又是spring的一个扩展点。
此方法为BeanFactory注册Post事件处理器，BeanPostProcessor是Bean的后置处理器，用于监听容器触发的事件，此接口有两个方法: postProcessBeforeInitialization 和 postProcessAfterInitialization分别会在Bean初始化之前和初始化之后得到执行。
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);}
五、initMessageSource()
初始化MessageSource信息源，即国际化处理、消息绑定、消息解析。
protected void initMessageSource() {//获取beanFactoryConfigurableListableBeanFactory beanFactory = getBeanFactory();//判断容器内是否包含消息组件if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {//如果有，则赋值给messageSourcethis.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.//如果没有则创建一个DelegatingMessageSourceDelegatingMessageSource dms = new DelegatingMessageSource();dms.setParentMessageSource(getInternalParentMessageSource());this.messageSource = dms;//把创建好的MessageSource注册在容器中，当能获取到国际化配置文件的值的时候，就可以自动注入MessageSourcebeanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);if (logger.isTraceEnabled()) {logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");}}}
六、initApplicationEventMulticaster()
初始化容器事件广播器，并放入applicationEventMulticaster bean中。
protected void initApplicationEventMulticaster() {//获取beanFactoryConfigurableListableBeanFactory beanFactory = getBeanFactory();//从beanFactory中获取事件广播器if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {//如果有，则赋值给applicationEventMulticasterthis.applicationEventMulticaster =beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);if (logger.isTraceEnabled()) {logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");}}else {//如果没有，则创建一个SimpleApplicationEventMulticasterthis.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);//讲创建的SimpleApplicationEventMulticaster注册到beanFactory中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() + "]");}}}
七、onRefresh()
又是一个扩展点，留给子类来初始化其他的bean。
protected void onRefresh() throws BeansException {// For subclasses: do nothing by default.}
八、registerListeners()
在所有注册的bean中查找ApplicationListener，为事件广播器注册事件监听器。
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!//从beanFactory中获取ApplicationListenerString[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);//将每个监听器添加到事件广播器中for (String listenerBeanName : listenerBeanNames) {getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);}// Publish early application events now that we finally have a multicaster...//注册之前步骤产生的事件监听器Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;this.earlyApplicationEvents = null;if (earlyEventsToProcess != null) {for (ApplicationEvent earlyEvent : earlyEventsToProcess) {getApplicationEventMulticaster().multicastEvent(earlyEvent);}}}
九、finishBeanFactoryInitialization(beanFactory)
这个方法就是负责初始化所有的没有设置懒加载的单实例bean。
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));}// 尽早初始化LoadTimeWeaverAware Bean，以便尽早注册其转换器String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);for (String weaverAwareName : weaverAwareNames) {getBean(weaverAwareName);}// Stop using the temporary ClassLoader for type matching.//为了使类型匹配，停止使用临时的类加载器beanFactory.setTempClassLoader(null);// Allow for caching all bean definition metadata, not expecting further changes.//缓存容器中所有注册的BeanDefinition元数据，以防被修改beanFactory.freezeConfiguration();// Instantiate all remaining (non-lazy-init) singletons.//对配置了lazy-init属性的单例模式的Bean进行预实例化处理beanFactory.preInstantiateSingletons();}
1、beanFactory.preInstantiateSingletons()是调用到DefaultListableBeanFactory的方法。
public void preInstantiateSingletons() throws BeansException {if (logger.isTraceEnabled()) {logger.trace("Pre-instantiating singletons in " + this);}// Iterate over a copy to allow for init methods which in turn register new bean definitions.// While this may not be part of the regular factory bootstrap, it does otherwise work fine.//获取容器中的所有bean，依次进行初始化和创建对象List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);// Trigger initialization of all non-lazy singleton beans...for (String beanName : beanNames) {//获取bean的定义信息RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);//bean不是抽象的、是单实例的、是懒加载的if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {//判断是否是FactoryBean，是否是实现FactoryBean接口的beanif (isFactoryBean(beanName)) {Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);if (bean instanceof FactoryBean) {final FactoryBean<?> factory = (FactoryBean<?>) bean;boolean isEagerInit;if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)((SmartFactoryBean<?>) factory)::isEagerInit,getAccessControlContext());}else {isEagerInit = (factory instanceof SmartFactoryBean &&((SmartFactoryBean<?>) factory).isEagerInit());}if (isEagerInit) {getBean(beanName);}}}else {//不是工厂Bean,利用getBean创建对象getBean(beanName);}}}// Trigger post-initialization callback for all applicable beans...for (String beanName : beanNames) {Object singletonInstance = getSingleton(beanName);if (singletonInstance instanceof SmartInitializingSingleton) {final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;if (System.getSecurityManager() != null) {AccessController.doPrivileged((PrivilegedAction<Object>) () -> {smartSingleton.afterSingletonsInstantiated();return null;}, getAccessControlContext());}else {smartSingleton.afterSingletonsInstantiated();}}}}
2、调用到AbstractBeanFactory.java类的getBean()方法
//通过name从IOC容器获取Bean@Overridepublic Object getBean(String name) throws BeansException {return doGetBean(name, null, null, false);}/*** 从IOC容器中获取Bean,此方法触发依赖注入*/@SuppressWarnings("unchecked")protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {//根据指定的名称获取被管理的Bean的名称，final String beanName = transformedBeanName(name);Object bean;//直接尝试从缓存获取或者singletonFactories中的ObjectFactory中获取// Eagerly check singleton cache for manually registered singletons.Object sharedInstance = getSingleton(beanName);if (sharedInstance != null && args == null) {if (logger.isTraceEnabled()) {//如果单例模式的Bean被创建，则直接返回if (isSingletonCurrentlyInCreation(beanName)) {logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +"' that is not fully initialized yet - a consequence of a circular reference");}else {logger.trace("Returning cached instance of singleton bean '" + beanName + "'");}}//获取给定Bean的实力对象，主要完成FactoryBean的相关处理bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);}else {// Fail if we're already creating this bean instance:// We're assumably within a circular reference.//缓存中没有单例模式的Bean,缓存中已经有原型模式的Bean,但是由于循环引用导致实例化对象失败if (isPrototypeCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName);}// Check if bean definition exists in this factory.//对IOC容器中是否存在指定名称的BeanDefinition进行检查，首先检查是否能在当前的BeanFactory中获取所需要的Bean//如果不能再委托当前容器的父容器去查找，如果还是找不到则沿着继承关系继续查找BeanFactory parentBeanFactory = getParentBeanFactory();//当前容器的父容器存在，且当前容器中不存在指定名称的Beanif (parentBeanFactory != null && !containsBeanDefinition(beanName)) {// Not found -> check parent.//解析指定Bean名称的原始名称String nameToLookup = originalBeanName(name);if (parentBeanFactory instanceof AbstractBeanFactory) {return ((AbstractBeanFactory) parentBeanFactory).doGetBean(nameToLookup, requiredType, args, typeCheckOnly);}//递归到beanFactory中寻找else if (args != null) {// Delegation to parent with explicit args.//委派父容器根据指定名称和显式的参数查找return (T) parentBeanFactory.getBean(nameToLookup, args);}else if (requiredType != null) {// No args -> delegate to standard getBean method.//委派父容器根据指定名称和类型查找return parentBeanFactory.getBean(nameToLookup, requiredType);}else {//委派父容器根据指定名称查找return (T) parentBeanFactory.getBean(nameToLookup);}}//创建的Bean是否需要进行类型验证if (!typeCheckOnly) {//向容器标记指定的Bean已经被创建markBeanAsCreated(beanName);}try {//根据指定Bean名称获取其父级Bean定义，主要解决Bean继承时子类和父类公共属性问题final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);checkMergedBeanDefinition(mbd, beanName, args);// Guarantee initialization of beans that the current bean depends on.//获取当前bean所有依赖Bean的名称String[] dependsOn = mbd.getDependsOn();//如果当前Bean有依赖if (dependsOn != null) {for (String dep : dependsOn) {if (isDependent(beanName, dep)) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");}//把能依赖Bean注册给当前依赖的BeanregisterDependentBean(dep, beanName);try {//递归调用，获取BeangetBean(dep);}catch (NoSuchBeanDefinitionException ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"'" + beanName + "' depends on missing bean '" + dep + "'", ex);}}}// Create bean instance.//创建单例模式的Bean的实例对象if (mbd.isSingleton()) {//调用匿名内部类创建Bean实例对象sharedInstance = getSingleton(beanName, () -> {try {return createBean(beanName, mbd, args);}catch (BeansException ex) {// Explicitly remove instance from singleton cache: It might have been put there// eagerly by the creation process, to allow for circular reference resolution.// Also remove any beans that received a temporary reference to the bean.//从单例模式的Bean缓存中清除实例对象destroySingleton(beanName);throw ex;}});//获取给定Bean的实力对象bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);}//IOC容器创建原型模式的Bean实例对象else if (mbd.isPrototype()) {// It's a prototype -> create a new instance.//prototype模式的创建（new）//原型模式每次都会创建一个新的对象Object prototypeInstance = null;try {//回调方法，注册当前创建的原型对象beforePrototypeCreation(beanName);//创建指定Bean的对象实例prototypeInstance = createBean(beanName, mbd, args);}finally {//回调方法，告诉IOC容器不再创建指定Bean的原型对象afterPrototypeCreation(beanName);}//获取指定Bean的实例对象bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);}else {//创建的Bean既不是单例模式也不是原型模式，创建其他生命周期的BeanString scopeName = mbd.getScope();final Scope scope = this.scopes.get(scopeName);//如果Bean定义资源中没有配置生命周期范围，则Bean定义不合法if (scope == null) {throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");}try {//调用匿名内部类，获取一个指定生命周期范围的实例Object scopedInstance = scope.get(beanName, () -> {beforePrototypeCreation(beanName);try {return createBean(beanName, mbd, args);}finally {afterPrototypeCreation(beanName);}});//获取指定Bean的实例对象bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);}catch (IllegalStateException ex) {throw new BeanCreationException(beanName,"Scope '" + scopeName + "' is not active for the current thread; consider " +"defining a scoped proxy for this bean if you intend to refer to it from a singleton",ex);}}}catch (BeansException ex) {cleanupAfterBeanCreationFailure(beanName);throw ex;}}// Check if required type matches the type of the actual bean instance.// 对创建的Bean实例对象进行类型检查if (requiredType != null && !requiredType.isInstance(bean)) {try {T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);if (convertedBean == null) {throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());}return convertedBean;}catch (TypeMismatchException ex) {if (logger.isTraceEnabled()) {logger.trace("Failed to convert bean '" + name + "' to required type '" +ClassUtils.getQualifiedName(requiredType) + "'", ex);}throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());}}return (T) bean;}
看了上方方法我们知道了原来Spring本身只定义了两种Scope，也知道了SpringMVC的几种Scope是如何实现的了。
然后发现一开始会先判断bean存不存在，如果存在就直接返回了。如果不存在那就要接着往下看createBean方法了.
3、继续调用到AbstractAutowireCapableBeanFactory的createBean()方法
/*** Central method of this class: creates a bean instance,* populates the bean instance, applies post-processors, etc.* @see #doCreateBean** 创建Bean实例对象*/@Overrideprotected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)throws BeanCreationException {if (logger.isTraceEnabled()) {logger.trace("Creating instance of bean '" + beanName + "'");}RootBeanDefinition mbdToUse = mbd;// Make sure bean class is actually resolved at this point, and// clone the bean definition in case of a dynamically resolved Class// which cannot be stored in the shared merged bean definition.// 判断需要创建的Bean是否可以实例化，即是否可以通过当前的类加载器加载Class<?> resolvedClass = resolveBeanClass(mbd, beanName);if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {mbdToUse = new RootBeanDefinition(mbd);mbdToUse.setBeanClass(resolvedClass);}// Prepare method overrides.//验证及准备覆盖的方法try {mbdToUse.prepareMethodOverrides();}catch (BeanDefinitionValidationException ex) {throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),beanName, "Validation of method overrides failed", ex);}try {// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.// 如果Bean配置了初始化前后的处理器，则返回一个需要创建Bean的代理对象Object bean = resolveBeforeInstantiation(beanName, mbdToUse);if (bean != null) {return bean;}}catch (Throwable ex) {throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,"BeanPostProcessor before instantiation of bean failed", ex);}try {//创建bean的入口Object beanInstance = doCreateBean(beanName, mbdToUse, args);if (logger.isTraceEnabled()) {logger.trace("Finished creating instance of bean '" + beanName + "'");}return beanInstance;}catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {// A previously detected exception with proper bean creation context already,// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.throw ex;}catch (Throwable ex) {throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);}}/*** 真正创建Bean的方法*/protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)throws BeanCreationException {// Instantiate the bean.//封装被创建的Bean对象BeanWrapper instanceWrapper = null;if (mbd.isSingleton()) {instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);}if (instanceWrapper == null) {//根据指定bean使用对应的策略创建新的实例，如：工厂方法、构造函数自动注入，简单初始化instanceWrapper = createBeanInstance(beanName, mbd, args);}final Object bean = instanceWrapper.getWrappedInstance();//获取实例化对象的类型Class<?> beanType = instanceWrapper.getWrappedClass();if (beanType != NullBean.class) {mbd.resolvedTargetType = beanType;}// Allow post-processors to modify the merged bean definition.//调用PostProcessor后置处理器synchronized (mbd.postProcessingLock) {if (!mbd.postProcessed) {try {applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);}catch (Throwable ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"Post-processing of merged bean definition failed", ex);}mbd.postProcessed = true;}}// Eagerly cache singletons to be able to resolve circular references// even when triggered by lifecycle interfaces like BeanFactoryAware.// 向容器中缓存单例模式的Bean对象，以防止循环引用boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&isSingletonCurrentlyInCreation(beanName));if (earlySingletonExposure) {if (logger.isTraceEnabled()) {logger.trace("Eagerly caching bean '" + beanName +"' to allow for resolving potential circular references");}//为避免后期循环依赖，尽早持有对象的引用addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));}// Initialize the bean instance.//Bean对象的初始化，依赖注入在此触发，这个对象在初始化完成之后返回依赖注入完成后的BeanObject exposedObject = bean;try {//将Bean实例对象封装，并且将Bean定义中配置的属性值赋给实例对象populateBean(beanName, mbd, instanceWrapper);//初始化Bean对象,Bean实例对象的依赖注入完成之后，为Bean实例对象应用BeanPostProcessor后置处理器exposedObject = initializeBean(beanName, exposedObject, mbd);}catch (Throwable ex) {if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {throw (BeanCreationException) ex;}else {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);}}if (earlySingletonExposure) {//获取指定名称的已注册的单例模式的Bean对象Object earlySingletonReference = getSingleton(beanName, false);if (earlySingletonReference != null) {//根据名称获取已注册的Bean和正在实例化的Bean是同一个if (exposedObject == bean) {//当前实例化的Bean初始化完成exposedObject = earlySingletonReference;}//当前Bean依赖其他Bean,并且当发生循环引用时不允许创建新的实例对象else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {String[] dependentBeans = getDependentBeans(beanName);Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);//获取当前Bean所依赖的其他Beanfor (String dependentBean : dependentBeans) {//对依赖Bean进行类型检查if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {actualDependentBeans.add(dependentBean);}}if (!actualDependentBeans.isEmpty()) {throw new BeanCurrentlyInCreationException(beanName,"Bean with name '" + beanName + "' has been injected into other beans [" +StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +"] in its raw version as part of a circular reference, but has eventually been " +"wrapped. This means that said other beans do not use the final version of the " +"bean. This is often the result of over-eager type matching - consider using " +"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");}}}}// Register bean as disposable.// 注册完成依赖注入的Beantry {registerDisposableBeanIfNecessary(beanName, bean, mbd);}catch (BeanDefinitionValidationException ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);}return exposedObject;}
到这里第一次初始化的bean也返回了。你以为就这样结束了么。不，还有几个很重要的点。
创建bean实例createBeanInstance ()
/*** Create a new instance for the specified bean, using an appropriate instantiation strategy:* factory method, constructor autowiring, or simple instantiation.* @param beanName the name of the bean* @param mbd the bean definition for the bean* @param args explicit arguments to use for constructor or factory method invocation* @return a BeanWrapper for the new instance* @see #obtainFromSupplier* @see #instantiateUsingFactoryMethod* @see #autowireConstructor* @see #instantiateBean** 创建Bean的实例对象*/protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {// Make sure bean class is actually resolved at this point.// 确认Bean是可实例化的Class<?> beanClass = resolveBeanClass(mbd, beanName);// 使用工厂方法对Bean进行实例化if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());}Supplier<?> instanceSupplier = mbd.getInstanceSupplier();if (instanceSupplier != null) {return obtainFromSupplier(instanceSupplier, beanName);}//调用工厂方法进行实例化if (mbd.getFactoryMethodName() != null) {return instantiateUsingFactoryMethod(beanName, mbd, args);}// Shortcut when re-creating the same bean...// 使用容器的自动装配方法进行实例化boolean resolved = false;boolean autowireNecessary = false;if (args == null) {synchronized (mbd.constructorArgumentLock) {//一个类有多个构造函数，每个构造函数都会不同的参数，所以调用前需要先根据参数缩影构造函数//和对应的工厂方法if (mbd.resolvedConstructorOrFactoryMethod != null) {resolved = true;autowireNecessary = mbd.constructorArgumentsResolved;}}}if (resolved) {if (autowireNecessary) {//配置了自动装配属性，使用容器的自动装配进行实例化，容器的自动装配根据参数类型匹配Bean的构造方法return autowireConstructor(beanName, mbd, null, null);}else {//使用默认构造函数构造return instantiateBean(beanName, mbd);}}// Candidate constructors for autowiring?// 使用Bean的构造方法进行实例化Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {//使用容器的自动装配特性，调用匹配的构造方法进行实例化return autowireConstructor(beanName, mbd, ctors, args);}// Preferred constructors for default construction?ctors = mbd.getPreferredConstructors();if (ctors != null) {return autowireConstructor(beanName, mbd, ctors, null);}// No special handling: simply use no-arg constructor.//使用默认构造函数构造return instantiateBean(beanName, mbd);}
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