Spring的refresh()方法相关异常解析

public void refresh() throws BeansException, IllegalStateException {
	synchronized (this.startupShutdownMonitor) {
		//刷新之前的准备工作，包括设置启动时间，是否激活标识位，初始化属性源(property source)配置
		prepareRefresh();
		//由子类去刷新BeanFactory(如果还没创建则创建)，并将BeanFactory返回
		ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
		//准备BeanFactory以供ApplicationContext使用
		prepareBeanFactory(beanFactory);
		try {
			//子类可通过格式此方法来对BeanFactory进行修改
			postProcessBeanFactory(beanFactory);
			//实例化并调用所有注册的BeanFactoryPostProcessor对象
			invokeBeanFactoryPostProcessors(beanFactory);
			//实例化并调用所有注册的BeanPostProcessor对象
			registerBeanPostProcessors(beanFactory);
			//初始化MessageSource
			initMessageSource();
			//初始化事件广播器
			initApplicationEventMulticaster();
			//子类覆盖此方法在刷新过程做额外工作
			onRefresh();
			//注册应用监听器ApplicationListener
			registerListeners();
			//实例化所有non-lazy-init bean
			finishBeanFactoryInitialization(beanFactory);
			//刷新完成工作，包括初始化LifecycleProcessor，发布刷新完成事件等
			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();//刷新BeanFactory,如果beanFactory为null，则创建
  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已经不为null，则销毁beanFactory中的Bean后自行关闭
    destroyBeans();
    closeBeanFactory();
  }
  try {
    DefaultListableBeanFactory beanFactory = createBeanFactory();//创建beanFactory
    beanFactory.setSerializationId(getId());
    customizeBeanFactory(beanFactory);
    loadBeanDefinitions(beanFactory);
    synchronized (this.beanFactoryMonitor) {
      this.beanFactory = beanFactory;//对beanFactory成员进行赋值
    }
  }
  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传递值为true，这样就自动调用了refresh方法进行了刷新
    refresh();
  }
}

@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;
  }
}

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) {//如果为null则抛异常
    throw new IllegalStateException("ApplicationEventMulticaster not initialized - " +
        "call 'refresh' before multicasting events via the context: " + this);
  }
  return this.applicationEventMulticaster;
}