Spring容器的创建过程源码解析

注：调试的Spring版本是4.3.12.RELEASE。

AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(Demo.class);

从AnnotationConfigApplicationContext创建开始进入：
类：AnnotationConfigApplicationContext.class

public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
		this();
		register(annotatedClasses);
		refresh();
	}

this()和register(annotatedClasses)方法主要是程序的预处理和解析。
refresh()是核心方法，完成容器的创建和刷工作。所以，主要的逻辑都是该方法完成的，也是我们主要解析的方法。

总体上来说Spring容器的创建过程大致可以分为：

1. BeanFactory的创建及预准备工作
2. 执行BeanFactoryPostProcessor
3. 注册BeanPostProcessor
4. 初始化MessageSource
5. 初始化事件派发器、监听器等
6. Bean创建
7. 容器创建完成
   以上也是本文的大纲结构。
   （以下中二级标题是分阶段的定义，四级标题是refresh方法的整个运行流程）

refresh方法如下：

@Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// Prepare the bean factory for use in this context.
			prepareBeanFactory(beanFactory);

			try {
				// Allows post-processing of the bean factory in context subclasses.
				postProcessBeanFactory(beanFactory);

				// Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);

				// Register bean processors that intercept bean creation.
				registerBeanPostProcessors(beanFactory);

				// Initialize message source for this context.
				initMessageSource();

				// Initialize event multicaster for this context.
				initApplicationEventMulticaster();

				// Initialize other special beans in specific context subclasses.
				onRefresh();

				// Check for listener beans and register them.
				registerListeners();

				// Instantiate all remaining (non-lazy-init) singletons.
				finishBeanFactoryInitialization(beanFactory);

				// Last step: publish corresponding event.
				finishRefresh();
			}

			catch (BeansException ex) {
				if (logger.isWarnEnabled()) {
					logger.warn("Exception encountered during context initialization - " +
							"cancelling refresh attempt: " + ex);
				}

				// Destroy already created singletons to avoid dangling resources.
				destroyBeans();

				// Reset 'active' flag.
				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();
			}
		}
	}

一、BeanFactory的创建及预准备工作

1、prepareRefresh()刷新前的预处理;

// Prepare this context for refreshing.
prepareRefresh();

调试进入prepareRefresh方法：
主要完成清除缓存，调用父类prepareRefresh方法

@Override
	protected void prepareRefresh() {
		this.scanner.clearCache();
		super.prepareRefresh();
	}

父类的prepareRefresh()方法如下：（记录一些状态、日志）

/**
	 * Prepare this context for refreshing, setting its startup date and
	 * active flag as well as performing any initialization of property sources.
	 */
	protected void prepareRefresh() {
		this.startupDate = System.currentTimeMillis();
		this.closed.set(false);
		this.active.set(true);

		if (logger.isInfoEnabled()) {
			logger.info("Refreshing " + this);
		}

		// Initialize any placeholder property sources in the context environment
		initPropertySources();

		// Validate that all properties marked as required are resolvable
		// see ConfigurablePropertyResolver#setRequiredProperties
		getEnvironment().validateRequiredProperties();

		// Allow for the collection of early ApplicationEvents,
		// to be published once the multicaster is available...
		this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
	}

重要方法说明：

1. initPropertySources()初始化一些属性设置;子类自定义个性化的属性设置方法；

	/**
	 * <p>Replace any stub property sources with actual instances.
	 * @see org.springframework.core.env.PropertySource.StubPropertySource
	 * @see org.springframework.web.context.support.WebApplicationContextUtils#initServletPropertySources
	 */
	protected void initPropertySources() {
		// For subclasses: do nothing by default.
	}

通过上面的源代码可以看到，这个方法是空的，注释“For subclasses: do nothing by default.”，说明这是为子类自定义个性化的方法。

2. getEnvironment().validateRequiredProperties();检验属性的合法等
3. earlyApplicationEvents= new LinkedHashSet();保存容器中的一些早期的事件；

2、obtainFreshBeanFactory();获取BeanFactory

// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

进入obtainFreshBeanFactory()方法：

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
		refreshBeanFactory();
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (logger.isDebugEnabled()) {
			logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
		}
		return beanFactory;
	}

重要方法说明：

1. refreshBeanFactory();刷新【创建】BeanFactory；
   创建了一个this.beanFactory = new DefaultListableBeanFactory();
   设置序列化的id
2. getBeanFactory();返回刚才GenericApplicationContext创建的BeanFactory对象；
3. 将创建的BeanFactory【DefaultListableBeanFactory】返回；

3、prepareBeanFactory(beanFactory);BeanFactory的预准备工作（执行完后就表示BeanFactory创建好了，也进行一些设置了）；

/**
	 * Configure the factory's standard context characteristics,
	 * such as the context's ClassLoader and post-processors.
	 * @param beanFactory the BeanFactory to configure
	 */
	protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		// Tell the internal bean factory to use the context's class loader etc.
		beanFactory.setBeanClassLoader(getClassLoader());
		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

		// Configure the bean factory with context callbacks.
		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.
		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));

		// 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)) {
			beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
		}
		if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
			beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
		}
	}

1. 设置BeanFactory的类加载器、支持表达式解析器…
2. 添加部分BeanPostProcessor【ApplicationContextAwareProcessor】
3. 设置忽略的自动装配的接口EnvironmentAware、EmbeddedValueResolverAware、xxx；
4. 注册可以解析的自动装配；我们能直接在任何组件中自动注入：
   BeanFactory、ResourceLoader、ApplicationEventPublisher、ApplicationContext
5. 添加BeanPostProcessor【ApplicationListenerDetector】
6. 添加编译时的AspectJ；
7. 给BeanFactory中注册一些能用的组件；
   environment【ConfigurableEnvironment】、systemProperties【Map<String, Object>】、systemEnvironment【Map<String, Object>】

4、postProcessBeanFactory(beanFactory);BeanFactory准备工作完成后进行的后置处理工作；

/**
	 * 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) {
	}

可以看到也是空方法，也就是说提供给子类重写的。
子类通过重写这个方法来在BeanFactory创建并预准备完成以后做进一步的设置。

二、执行BeanFactoryPostProcessor

5、invokeBeanFactoryPostProcessors(beanFactory);执行BeanFactoryPostProcessor的方法；

BeanFactoryPostProcessor：BeanFactory的后置处理器。在BeanFactory标准初始化之后执行的；
两个接口：BeanFactoryPostProcessor、BeanDefinitionRegistryPostProcessor(给容器中额外添加组件的)

/**
	 * Instantiate and invoke all registered BeanFactoryPostProcessor beans,
	 * respecting explicit order if given.
	 * <p>Must be called before singleton instantiation.
	 */
	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()));
		}
	}

执行BeanFactoryPostProcessor的方法；

• 先执行BeanDefinitionRegistryPostProcessor

• 获取所有的BeanDefinitionRegistryPostProcessor；

• 看先执行实现了PriorityOrdered优先级接口的BeanDefinitionRegistryPostProcessor、postProcessor.postProcessBeanDefinitionRegistry(registry)

• 在执行实现了Ordered顺序接口的BeanDefinitionRegistryPostProcessor；
  postProcessor.postProcessBeanDefinitionRegistry(registry)

• 最后执行没有实现任何优先级或者是顺序接口的BeanDefinitionRegistryPostProcessors；
  postProcessor.postProcessBeanDefinitionRegistry(registry)

• 再执行BeanFactoryPostProcessor的方法

• 获取所有的BeanFactoryPostProcessor

• 看先执行实现了PriorityOrdered优先级接口的BeanFactoryPostProcessor、postProcessor.postProcessBeanFactory()

• 在执行实现了Ordered顺序接口的BeanFactoryPostProcessor；
  postProcessor.postProcessBeanFactory()

• 最后执行没有实现任何优先级或者是顺序接口的BeanFactoryPostProcessor；
  postProcessor.postProcessBeanFactory()

三、注册BeanPostProcessor

6、registerBeanPostProcessors(beanFactory);注册BeanPostProcessor（Bean的后置处理器）【 intercept bean creation拦截Bean的创建过程】

/**
	 * Instantiate and invoke all registered 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);
	}

这里面就调用了registerBeanPostProcessors，如下：

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<BeanPostProcessor>();
		List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
		List<String> orderedPostProcessorNames = new ArrayList<String>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
		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<BeanPostProcessor>();
		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<BeanPostProcessor>();
		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));
	}

需要注意的是：不同接口类型的BeanPostProcessor；在Bean创建前后的执行时机是不一样的。

BeanPostProcessor的子接口有：

• DestructionAwareBeanPostProcessor
• InstantiationAwareBeanPostProcessor
• SmartInstantiationAwareBeanPostProcessor、
• MergedBeanDefinitionPostProcessor【internalPostProcessors】

1. 获取所有的 BeanPostProcessor;后置处理器都默认可以通过PriorityOrdered、Ordered接口来执行优先级
2. 先注册PriorityOrdered优先级接口的BeanPostProcessor；
   把每一个BeanPostProcessor；添加到BeanFactory中
   beanFactory.addBeanPostProcessor(postProcessor);
3. 再注册Ordered接口的
4. 最后注册没有实现任何优先级接口的
5. 最终注册MergedBeanDefinitionPostProcessor；
6. 注册一个ApplicationListenerDetector；来在Bean创建完成后检查是否是ApplicationListener，如果是applicationContext.addApplicationListener((ApplicationListener<?>) bean);

四、初始化MessageSource

7、initMessageSource();初始化MessageSource组件（做国际化功能；消息绑定，消息解析）；

	/**
	 * 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.isDebugEnabled()) {
				logger.debug("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.isDebugEnabled()) {
				logger.debug("Unable to locate MessageSource with name '" + MESSAGE_SOURCE_BEAN_NAME +
						"': using default [" + this.messageSource + "]");
			}
		}
	}

1. 获取BeanFactory。
   方法的第一行：ConfigurableListableBeanFactory beanFactory = getBeanFactory();
2. 看容器中是否有id为messageSource的，类型是MessageSource的组件
   如果有则赋值给messageSource，如果没有则自己创建一个DelegatingMessageSource；
   MessageSource：取出国际化配置文件中的某个key的值；能按照区域信息获取；
3. 把创建好的MessageSource注册在容器中，以后获取国际化配置文件的值的时候，可以自动注入MessageSource；
   beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
   MessageSource.getMessage(String code, Object[] args, String defaultMessage, Locale locale);

五、初始化事件派发器、监听器等

8、initApplicationEventMulticaster();初始化事件派发器；

/**
	 * 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.isDebugEnabled()) {
				logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
			}
		}
		else {
			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 + "]");
			}
		}
	}

1. 获取BeanFactory
2. 从BeanFactory中获取applicationEventMulticaster的ApplicationEventMulticaster；
3. 如果上一步没有配置；创建一个SimpleApplicationEventMulticaster
4. 将创建的ApplicationEventMulticaster添加到BeanFactory中，以后其他组件直接自动注入

9、onRefresh();留给子容器（子类）

	/**
	 * 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.
	}

子类重写这个方法，在容器刷新的时候可以自定义逻辑；

10、registerListeners();给容器中将所有项目里面的ApplicationListener注册进来；

	/**
	 * 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);
			}
		}
	}

1. 从容器中拿到所有的ApplicationListener
   上面的代码：String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
2. 将每个监听器添加到事件派发器中；
   getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
3. 派发之前步骤产生的事件；

六、Bean创建

11、finishBeanFactoryInitialization(beanFactory);初始化所有剩下的单实例bean；

	/**
	 * 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(new StringValueResolver() {
				@Override
				public String resolveStringValue(String strVal) {
					return 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();
	}

最主要的方法是最后的**beanFactory.preInstantiateSingletons();**初始化后剩下的单实例bean

打开preInstantiateSingletons()源码：

	@Override
	public void preInstantiateSingletons() throws BeansException {
		if (this.logger.isDebugEnabled()) {
			this.logger.debug("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.
		List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);

		// Trigger initialization of all non-lazy singleton beans...
		for (String beanName : beanNames) {
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
				if (isFactoryBean(beanName)) {
					final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
					boolean isEagerInit;
					if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
						isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
							@Override
							public Boolean run() {
								return ((SmartFactoryBean<?>) factory).isEagerInit();
							}
						}, getAccessControlContext());
					}
					else {
						isEagerInit = (factory instanceof SmartFactoryBean &&
								((SmartFactoryBean<?>) factory).isEagerInit());
					}
					if (isEagerInit) {
						getBean(beanName);
					}
				}
				else {
					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(new PrivilegedAction<Object>() {
						@Override
						public Object run() {
							smartSingleton.afterSingletonsInstantiated();
							return null;
						}
					}, getAccessControlContext());
				}
				else {
					smartSingleton.afterSingletonsInstantiated();
				}
			}
		}
	}

1、获取容器中的所有Bean，依次进行初始化和创建对象

2、获取Bean的定义信息；RootBeanDefinition

3、Bean不是抽象的，是单实例的，是懒加载；

1. 判断是否是FactoryBean；是否是实现FactoryBean接口的Bean；
2. 不是工厂Bean。利用getBean(beanName);创建对象

(2.1) getBean(beanName)；其实就是我们自己代码中通过容器获取Bean时调用的getBean();方法

	@Override
	public Object getBean(String name) throws BeansException {
		return doGetBean(name, null, null, false);
	}

(2.2) doGetBean(name, null, null, false);

	/**
	 * Return an instance, which may be shared or independent, of the specified bean.
	 * @param name the name of the bean to retrieve
	 * @param requiredType the required type of the bean to retrieve
	 * @param args arguments to use when creating a bean instance using explicit arguments
	 * (only applied when creating a new instance as opposed to retrieving an existing one)
	 * @param typeCheckOnly whether the instance is obtained for a type check,
	 * not for actual use
	 * @return an instance of the bean
	 * @throws BeansException if the bean could not be created
	 */
	@SuppressWarnings("unchecked")
	protected <T> T doGetBean(
			final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
			throws BeansException {

		final String beanName = transformedBeanName(name);
		Object bean;

		// Eagerly check singleton cache for manually registered singletons.
		Object sharedInstance = getSingleton(beanName);
		if (sharedInstance != null && args == null) {
			if (logger.isDebugEnabled()) {
				if (isSingletonCurrentlyInCreation(beanName)) {
					logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
							"' that is not fully initialized yet - a consequence of a circular reference");
				}
				else {
					logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
				}
			}
			bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
		}

		else {
			// Fail if we're already creating this bean instance:
			// We're assumably within a circular reference.
			if (isPrototypeCurrentlyInCreation(beanName)) {
				throw new BeanCurrentlyInCreationException(beanName);
			}

			// Check if bean definition exists in this factory.
			BeanFactory parentBeanFactory = getParentBeanFactory();
			if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
				// Not found -> check parent.
				String nameToLookup = originalBeanName(name);
				if (args != null) {
					// Delegation to parent with explicit args.
					return (T) parentBeanFactory.getBean(nameToLookup, args);
				}
				else {
					// No args -> delegate to standard getBean method.
					return parentBeanFactory.getBean(nameToLookup, requiredType);
				}
			}

			if (!typeCheckOnly) {
				markBeanAsCreated(beanName);
			}

			try {
				final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
				checkMergedBeanDefinition(mbd, beanName, args);

				// Guarantee initialization of beans that the current bean depends on.
				String[] dependsOn = mbd.getDependsOn();
				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 + "'");
						}
						registerDependentBean(dep, beanName);
						getBean(dep);
					}
				}

				// Create bean instance.
				if (mbd.isSingleton()) {
					sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
						@Override
						public Object getObject() throws BeansException {
							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.
								destroySingleton(beanName);
								throw ex;
							}
						}
					});
					bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
				}

				else if (mbd.isPrototype()) {
					// It's a prototype -> create a new instance.
					Object prototypeInstance = null;
					try {
						beforePrototypeCreation(beanName);
						prototypeInstance = createBean(beanName, mbd, args);
					}
					finally {
						afterPrototypeCreation(beanName);
					}
					bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
				}

				else {
					String scopeName = mbd.getScope();
					final Scope scope = this.scopes.get(scopeName);
					if (scope == null) {
						throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
					}
					try {
						Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
							@Override
							public Object getObject() throws BeansException {
								beforePrototypeCreation(beanName);
								try {
									return createBean(beanName, mbd, args);
								}
								finally {
									afterPrototypeCreation(beanName);
								}
							}
						});
						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.
		if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
			try {
				return getTypeConverter().convertIfNecessary(bean, requiredType);
			}
			catch (TypeMismatchException ex) {
				if (logger.isDebugEnabled()) {
					logger.debug("Failed to convert bean '" + name + "' to required type '" +
							ClassUtils.getQualifiedName(requiredType) + "'", ex);
				}
				throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
			}
		}
		return (T) bean;
	}

(2.3) 从doGet方法中，可以看到：先获取缓存中保存的单实例Bean。如果能获取到说明这个Bean之前被创建过（所有创建过的单实例Bean都会被缓存起来）。
从private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(256); // 这里面保存了所有的单实例的Bean
(2.4) 缓存中获取不到，开始Bean的创建对象流程；
(2.5) 标记当前bean已经被创建（防止多线程情况下，重复创建同一个Bean）
(2.6) 获取Bean的定义信息；
(2.7) 获取当前Bean依赖的其他Bean;如果有按照getBean()把依赖的Bean先创建出来；
(2.8) 启动单实例Bean的创建流程；

• createBean(beanName, mbd, args);
• Object bean = resolveBeforeInstantiation(beanName, mbdToUse);让BeanPostProcessor先拦截返回代理对象；
  【InstantiationAwareBeanPostProcessor】：提前执行；
  先触发：postProcessBeforeInstantiation()；
  如果有返回值：触发postProcessAfterInitialization()；
• 如果前面的InstantiationAwareBeanPostProcessor没有返回代理对象，则继续执行）
• Object beanInstance = doCreateBean(beanName, mbdToUse, args);创建Bean
  A、【创建Bean实例】；createBeanInstance(beanName, mbd, args);
  利用工厂方法或者对象的构造器创建出Bean实例；
  B、applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
  调用MergedBeanDefinitionPostProcessor的postProcessMergedBeanDefinition(mbd, beanType, beanName);
  C、【Bean属性赋值】populateBean(beanName, mbd, instanceWrapper);
  赋值之前：
  a. 拿到InstantiationAwareBeanPostProcessor后置处理器；postProcessAfterInstantiation()；
  b. 拿到InstantiationAwareBeanPostProcessor后置处理器；postProcessPropertyValues()；
  赋值：
  c. 应用Bean属性的值；为属性利用setter方法等进行赋值；
  applyPropertyValues(beanName, mbd, bw, pvs);
  D、【Bean初始化】initializeBean(beanName, exposedObject, mbd);
  a. 【执行Aware接口方法】invokeAwareMethods(beanName, bean);执行xxxAware接口的方法
  BeanNameAware\BeanClassLoaderAware\BeanFactoryAware
  b. 【执行后置处理器初始化之前】applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
  BeanPostProcessor.postProcessBeforeInitialization（）;
  c. 【执行初始化方法】invokeInitMethods(beanName, wrappedBean, mbd);
  是否是InitializingBean接口的实现；执行接口规定的初始化；
  是否自定义初始化方法；
  d. 【执行后置处理器初始化之后】applyBeanPostProcessorsAfterInitialization
  BeanPostProcessor.postProcessAfterInitialization()；
  E、注册Bean的销毁方法；
• 将创建的Bean添加到缓存中singletonObjects；
  ioc容器就是这些Map；很多的Map里面保存了单实例Bean，环境信息等等。这个singletonObjects大Map就构成了容器。容器中保存了所有的组件。

4、所有Bean都利用getBean创建完成以后；检查所有的Bean是否是SmartInitializingSingleton接口的；如果是；就执行afterSingletonsInstantiated()；

七、容器创建完成

	/**
	 * Finish the refresh of this context, invoking the LifecycleProcessor's
	 * onRefresh() method and publishing the
	 * {@link org.springframework.context.event.ContextRefreshedEvent}.
	 */
	protected void finishRefresh() {
		// 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);
	}

12、finishRefresh();完成BeanFactory的初始化创建工作；IOC容器创建完成(11已经完成了)；

1. initLifecycleProcessor();初始化和生命周期有关的后置处理器；LifecycleProcessor
   默认从容器中找是否有lifecycleProcessor的组件【LifecycleProcessor】；如果没有new DefaultLifecycleProcessor();
   加入到容器；
   写一个LifecycleProcessor的实现类，可以在BeanFactory的onRefresh()或者onClose()生命周期处进行拦截
   写一个LifecycleProcessor的实现类，可以在BeanFactory
2. getLifecycleProcessor().onRefresh();
   拿到前面定义的生命周期处理器（BeanFactory）；回调onRefresh()；
3. publishEvent(new ContextRefreshedEvent(this));发布容器即刷新完成事件；
4. liveBeansView.registerApplicationContext(this);

总结：

1. Spring容器在启动的时候，先会保存所有注册进来的Bean的定义信息；
（未来就会根据这些Bean的定义信息，使用BeanFactory创建Bean对象）
Bean的定义有两种方式：
一种是：xml注册bean；<bean />
一种是：注解注册Bean；@Service、@Component、@Bean、xxx

2. 有了这些Bean定义信息后，Spring容器会在合适的时机创建这些Bean
所谓合适的时机，主要有两个：
一个是：用到这个bean的时候；利用getBean创建bean；创建好以后保存在容器中；
一个是：统一创建剩下所有的bean的时候；finishBeanFactoryInitialization()；
3. 对象创建最核心的思想是：后置处理器机制；BeanPostProcessor
每一个bean创建完成，都会使用各种后置处理器进行处理，来增强bean的功能；
举例来说：

AutowiredAnnotationBeanPostProcessor:处理自动注入
AnnotationAwareAspectJAutoProxyCreator:创建代理对象，来做AOP功能；
xxx....

增强的功能注解：
AsyncAnnotationBeanPostProcessor：支持异步注解的
任务调度等等...

4. 另外一个重要的机制：事件驱动模型
ApplicationListener；事件监听；
ApplicationEventMulticaster；事件派发