public void refresh() throws BeansException, IllegalStateException {
	synchronized (this.startupShutdownMonitor) {
		//重新整理之前的準備工作，包括設定啟動時間，是否啟用標識位，初始化屬性源(property source)配置
		prepareRefresh();

		//由子類去重新整理BeanFactory(如果還沒建立則建立)，並將BeanFactory返回
		ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

		//準備BeanFactory以供ApplicationContext使用
		prepareBeanFactory(beanFactory);

		try {
			//子類可通過格式此方法來對BeanFactory進行修改
			postProcessBeanFactory(beanFactory);

			//例項化並呼叫所有註冊的BeanFactoryPostProcessor物件
			invokeBeanFactoryPostProcessors(beanFactory);

			//例項化並呼叫所有註冊的BeanPostProcessor物件
			registerBeanPostProcessors(beanFactory);

			//初始化MessageSource
			initMessageSource();

			//初始化事件廣播器
			initApplicationEventMulticaster();

			//子類覆蓋此方法在重新整理過程做額外工作
			onRefresh();

			//註冊應用監聽器ApplicationListener
			registerListeners();

			//例項化所有non-lazy-init bean
			finishBeanFactoryInitialization(beanFactory);

			//重新整理完成工作，包括初始化LifecycleProcessor，釋出重新整理完成事件等
			finishRefresh();
		}

		catch (BeansException ex) {
			// Destroy already created singletons to avoid dangling resources.
			destroyBeans();

			// Reset 'active' flag.
			cancelRefresh(ex);

			// Propagate exception to caller.
			throw ex;
		}
	}
}
 

protected void finishRefresh() {
	// //初始化LifecycleProcessor
	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);
}
 

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
	refreshBeanFactory();//重新整理BeanFactory,如果beanFactory為null，則建立
	ConfigurableListableBeanFactory beanFactory = getBeanFactory();
	if (logger.isDebugEnabled()) {
		logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
	}
	return beanFactory;
}

@Override
protected final void refreshBeanFactory() throws BeansException {
	if (hasBeanFactory()) {//如果beanFactory已經不為null，則銷燬beanFactory中的Bean後自行關閉
		destroyBeans();
		closeBeanFactory();
	}
	try {
		DefaultListableBeanFactory beanFactory = createBeanFactory();//建立beanFactory
		beanFactory.setSerializationId(getId());
		customizeBeanFactory(beanFactory);
		loadBeanDefinitions(beanFactory);
		synchronized (this.beanFactoryMonitor) {
			this.beanFactory = beanFactory;//對beanFactory成員進行賦值
		}
	}
	catch (IOException ex) {
		throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
	}
}

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. public static void main(String[] args) {
	ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext();
	applicationContext.setConfigLocation("application-context.xml");
	applicationContext.start();
	applicationContext.close();
}
2. public static void main(String[] args) {
	ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext();
	applicationContext.setConfigLocation("application-context.xml");
	applicationContext.getBean("xtayfjpk");
	applicationContext.close();
}
3. public static void main(String[] args) {
	GenericApplicationContext parent = new GenericApplicationContext();
	AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
	context.setParent(parent);
	context.refresh();
	context.start();
	context.close();
}

public void start() {
	getLifecycleProcessor().start();
	publishEvent(new ContextStartedEvent(this));
}

public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) throws BeansException {
	super(parent);
	setConfigLocations(configLocations);
	if (refresh) {//refresh傳遞值為true，這樣就自動呼叫了refresh方法進行了重新整理
		refresh();
	}
}

第二條異常訊息，異常堆疊出錯在applicationContext.getBean("xtayfjpk")，applicationContext.getBean()方法呼叫的是上下文中beanFactory的getBean()方法實現的，獲取BeanFactory物件的程式碼在其基類ConfigurableListableBeanFactory中的getBeanFactory()方法中：

@Override
public final ConfigurableListableBeanFactory getBeanFactory() {
	synchronized (this.beanFactoryMonitor) {
		if (this.beanFactory == null) {
			throw new IllegalStateException("BeanFactory not initialized or already closed - " +
					"call 'refresh' before accessing beans via the ApplicationContext");
		}
		return this.beanFactory;
	}
}

第三條異常訊息，異常堆疊出錯在context.refresh()，但是如果沒有設定父上下文的話context.setParent(parent)，例子程式碼是不會出現異常的。這是因為在refresh方法中的finishRefresh()方法呼叫了publishEvent方法：

public void publishEvent(ApplicationEvent event) {
	Assert.notNull(event, "Event must not be null");
	if (logger.isTraceEnabled()) {
		logger.trace("Publishing event in " + getDisplayName() + ": " + event);
	}
	getApplicationEventMulticaster().multicastEvent(event);
	if (this.parent != null) {
		this.parent.publishEvent(event);
	}
}

private ApplicationEventMulticaster getApplicationEventMulticaster() throws IllegalStateException {
	if (this.applicationEventMulticaster == null) {//如果為null則拋異常
		throw new IllegalStateException("ApplicationEventMulticaster not initialized - " +
				"call 'refresh' before multicasting events via the context: " + this);
	}
	return this.applicationEventMulticaster;
}

綜上所述，其實這三條異常訊息的根本原因只有一個，就是當一個上下文物件建立後沒有呼叫refresh()方法。在Spring中ApplicationContext實現類有很多，有些實現類在建立的過程中自動呼叫了refresh()方法，而有些又沒有，如果沒有則需要自己手動呼叫refresh()方法。一般說來實現WebApplicationContext介面的實現類以及使用預設構造方法建立上下文物件時不會自動refresh()方法，其它情況則會自動呼叫。