Spring IoC源码：finishRefresh 完成刷新详解

Spring源码系列：

Spring IOC源码：简单易懂的Spring IOC 思路介绍
Spring IOC源码：核心流程介绍
Spring IOC源码：ApplicationContext刷新前准备工作
Spring IOC源码：obtainFreshBeanFactory 详解（上）
Spring IOC源码：obtainFreshBeanFactory 详解（中）
Spring IOC源码：obtainFreshBeanFactory 详解（下）
Spring IOC源码：＜context:component-scan＞源码详解
Spring IOC源码：invokeBeanFactoryPostProcessors 后置处理器详解
Spring IOC源码：registerBeanPostProcessors 详解
Spring IOC源码：实例化前的准备工作
Spring IOC源码：finishBeanFactoryInitialization详解
Spring IoC源码：getBean 详解
Spring IoC源码：createBean（ 上）
Spring IoC源码：createBean（ 中）
Spring IoC源码：createBean（ 下）
Spring IoC源码：finishRefresh 完成刷新详解

前言

当完成Bean定义信息解析、Bean的创建、初始化流程之后，到最后一个方法finishRefresh完成上下文刷新。

正文

来到refresh()方法中的最后一个方法finishRefresh();

public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// 容器刷新前准备工作
			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.
			//创建Bean工厂，解析配置
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// bean工厂准备工作
			prepareBeanFactory(beanFactory);

			try {
				//拓展接口，留给子类进行实现拓展
				postProcessBeanFactory(beanFactory);

				// 注册执行，BeanFactoryPostProcessor
				invokeBeanFactoryPostProcessors(beanFactory);

				// 注册创建BeanPostProcessor
				registerBeanPostProcessors(beanFactory);

				// 这个方法主要作用就是使用国际化，定制不同的消息文本，比如定义了一个Person的Bean，它有name属性，我们需要在不同的国家展示对应国家所在语言名称，这时候就可以使用国际化了。
				initMessageSource();

				// Initialize event multicaster for this context.
				//初始化应用事件广播器
				initApplicationEventMulticaster();

				// Initialize other special beans in specific context subclasses.
				//拓展接口，留给子类进行实现拓展，springboot就对该方法进行了处理
				onRefresh();

				// Check for listener beans and register them.
				//将内部的、以及我们自定义的监听器添加到缓存中，为后续逻辑处理做准备。还有添加事件源到缓存中。
				registerListeners();

				// Instantiate all remaining (non-lazy-init) singletons.
				//实例化剩下非懒加载的Bean
				finishBeanFactoryInitialization(beanFactory);

				// Last step: publish corresponding event.
				//使用应用事件广播器推送上下文刷新完毕事件（ContextRefreshedEvent ）到相应的监听器。
				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.
				//执行相关销毁方法
				destroyBeans();

				// Reset 'active' flag.
				//重置上下文刷新状态
				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();
			}
		}
	}

finishRefresh()，见方法1详解

方法1：finishRefresh

	protected void finishRefresh() {
		// Clear context-level resource caches (such as ASM metadata from scanning).
		//清除该资源加载器中的所有资源缓存
		clearResourceCaches();

		// Initialize lifecycle processor for this context.
		//初始化LifecycleProcessor。
		initLifecycleProcessor();

		// Propagate refresh to lifecycle processor first.
		//调用LifecycleProcessor的onRefresh方法进行刷新
		getLifecycleProcessor().onRefresh();

		// 发布事件
		publishEvent(new ContextRefreshedEvent(this));

		// Participate in LiveBeansView MBean, if active.
		LiveBeansView.registerApplicationContext(this);
	}

initLifecycleProcessor()，见方法2详解

getLifecycleProcessor().onRefresh()，见方法3详解

publishEvent(new ContextRefreshedEvent(this))，见方法4详解

方法2：initLifecycleProcessor

	protected void initLifecycleProcessor() {
		//获取BeanFactory工厂
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		//判断是否存在名称为lifecycleProcessor的Bean或定义信息
		if (beanFactory.containsLocalBean(LIFECYCLE_PROCESSOR_BEAN_NAME)) {
			//获取或创建LifecycleProcessor
			this.lifecycleProcessor =
					beanFactory.getBean(LIFECYCLE_PROCESSOR_BEAN_NAME, LifecycleProcessor.class);
			if (logger.isTraceEnabled()) {
				logger.trace("Using LifecycleProcessor [" + this.lifecycleProcessor + "]");
			}
		}
		else {
			//bean工厂中不存在该bean的信息，则创建一个默认的
			DefaultLifecycleProcessor defaultProcessor = new DefaultLifecycleProcessor();
			defaultProcessor.setBeanFactory(beanFactory);
			this.lifecycleProcessor = defaultProcessor;
			//注册添加到一级缓存中
			beanFactory.registerSingleton(LIFECYCLE_PROCESSOR_BEAN_NAME, this.lifecycleProcessor);
			if (logger.isTraceEnabled()) {
				logger.trace("No '" + LIFECYCLE_PROCESSOR_BEAN_NAME + "' bean, using " +
						"[" + this.lifecycleProcessor.getClass().getSimpleName() + "]");
			}
		}
	}

方法3：onRefresh

	public void onRefresh() {
		startBeans(true);
		this.running = true;
	}

private void startBeans(boolean autoStartupOnly) {
		//获取Lifecycle类型的bean集合
		Map<String, Lifecycle> lifecycleBeans = getLifecycleBeans();
		Map<Integer, LifecycleGroup> phases = new HashMap<>();
		lifecycleBeans.forEach((beanName, bean) -> {
			//autoStartupOnly 为true时，代表是容器自动启动调用，这时只有SmartLifecycle 类型且isAutoStartup为TRUE才会调用
			//如果autoStartupOnly 为false，代表是手动调用，会调用所有的Lifecycle
			if (!autoStartupOnly || (bean instanceof SmartLifecycle && ((SmartLifecycle) bean).isAutoStartup())) {
				//获取阶段值，即优先级值。如果有实现Phased接口，则通过getPhase方法返回数值，值越小则排序越前
				int phase = getPhase(bean);
				//判断容器中是否已存在，不存在则创建LifecycleGroup 类型对象
				LifecycleGroup group = phases.get(phase);
				if (group == null) {
					group = new LifecycleGroup(phase, this.timeoutPerShutdownPhase, lifecycleBeans, autoStartupOnly);
					phases.put(phase, group);
				}
				group.add(beanName, bean);
			}
		});
		if (!phases.isEmpty()) {
			List<Integer> keys = new ArrayList<>(phases.keySet());
			//排序
			Collections.sort(keys);
			//遍历调用
			for (Integer key : keys) {
				phases.get(key).start();
			}
		}
	}

方法4：publishEvent

protected void publishEvent(Object event, @Nullable ResolvableType eventType) {
		Assert.notNull(event, "Event must not be null");

		// Decorate event as an ApplicationEvent if necessary
		//判断事件是否继承了ApplicationEvent接口
		ApplicationEvent applicationEvent;
		if (event instanceof ApplicationEvent) {
			applicationEvent = (ApplicationEvent) event;
		}
		else {
			//将事件封装成PayloadApplicationEvent类型的事件
			applicationEvent = new PayloadApplicationEvent<>(this, event);
			//设置事件类型
			if (eventType == null) {
				eventType = ((PayloadApplicationEvent<?>) applicationEvent).getResolvableType();
			}
		}

		// Multicast right now if possible - or lazily once the multicaster is initialized
		if (this.earlyApplicationEvents != null) {
			this.earlyApplicationEvents.add(applicationEvent);
		}
		else {
			//使用多播器发布事件
			getApplicationEventMulticaster().multicastEvent(applicationEvent, eventType);
		}

		// Publish event via parent context as well...
		//使用父上下文进行发布事件
		if (this.parent != null) {
			if (this.parent instanceof AbstractApplicationContext) {
				((AbstractApplicationContext) this.parent).publishEvent(event, eventType);
			}
			else {
				this.parent.publishEvent(event);
			}
		}
	}

getApplicationEventMulticaster().multicastEvent(applicationEvent, eventType)，见方法5详解

方法5：multicastEvent

	public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
		//获取事件源类型
		ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
		Executor executor = getTaskExecutor();
		//根据事件类型获取对应类型的监听器
		for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {
			//调用监听器的onApplicationEvent方法
			if (executor != null) {
				executor.execute(() -> invokeListener(listener, event));
			}
			else {
				invokeListener(listener, event);
			}
		}
	}

invokeListener(listener, event))，见方法6详解

方法6：invokeListener

	protected void invokeListener(ApplicationListener<?> listener, ApplicationEvent event) {
		//获取错误处理器
		ErrorHandler errorHandler = getErrorHandler();
		if (errorHandler != null) {
			try {
			//调用监听器处理方法
				doInvokeListener(listener, event);
			}
			catch (Throwable err) {
				errorHandler.handleError(err);
			}
		}
		else {
			doInvokeListener(listener, event);
		}
	}

doInvokeListener(listener, event)，见方法7详解

方法7：doInvokeListener

private void doInvokeListener(ApplicationListener listener, ApplicationEvent event) {
		try {
			//调用监听器的onApplicationEvent方法，并传入事件
			listener.onApplicationEvent(event);
		}
		catch (ClassCastException ex) {
			String msg = ex.getMessage();
			if (msg == null || matchesClassCastMessage(msg, event.getClass())) {
				// Possibly a lambda-defined listener which we could not resolve the generic event type for
				// -> let's suppress the exception and just log a debug message.
				Log logger = LogFactory.getLog(getClass());
				if (logger.isTraceEnabled()) {
					logger.trace("Non-matching event type for listener: " + listener, ex);
				}
			}
			else {
				throw ex;
			}
		}
	}

总结

Spring IOC中refresh()所有方法都讲解完了，这里面的内容非车多，花了不少时间在看，但是感觉还是比较粗糙，文章中有很多点理解得不是很到位，如果大家有更好的见解，欢迎指点评论。学习IOC过程是非常枯燥的，但是耐心去看真的能发现这个框架设计真的很厉害，拓展性做得很好，有很多地方值得我们在工作中进行参考开发。后续会发布Spring 系列的其它文章，如AOP，只有不断的学习，才能加深对Spring框架的理解。