Spring ioc容器启动流程

     本文以XmlWebApplicationContext启动为例说明Spring ioc容器启动流程。

概览

AbstractApplicationContext的refresh()方法

具体步骤实现

prepareRefresh

AbstractApplicationContext.java

protected void prepareRefresh() {
		this.startupDate = System.currentTimeMillis();

		synchronized (this.activeMonitor) {
			this.active = 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();
	}

obtainFreshBeanFactory

        创建beanFactory实例，且解析xml配置文件，加载其中的bean到beanFactory中，详细见http://blog.csdn.net/architect0719/article/details/53066451。

prepareBeanFactory

         对创建的DefaultListableBeanFactory进行初始化，主要对其进行Context特性相关属性初始化工作，需要注意的是该初始化工作在其加载完bean之后：

AbstractApplicationContext.java

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
	// 设置DefaultListableBeanFactory的classLoader为context的class loader	
	beanFactory.setBeanClassLoader(getClassLoader());
	beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver());
	beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

	// 对bean factory设置context回调.
	beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
	beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
	beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
	beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
	beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
	beanFactory.ignoreDependencyInterface(EnvironmentAware.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);

	// 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());
	}
}

postProcessBeanFactory

          对BeanFactory增加BeanPostProcessor以及注册request/session scopes等：

AbstractRefreshableWebApplicationContext.java

/**
 * Register request/session scopes, a {@link ServletContextAwareProcessor}, etc.
 */
@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
	beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
	beanFactory.ignoreDependencyInterface(ServletContextAware.class);
	beanFactory.ignoreDependencyInterface(ServletConfigAware.class);

	WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
	WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
}

invokeBeanFactoryPostProcessors

         回调Context所有的BeanFactoryPostProcessor：

AbstractApplicationContext.java

/**
 * Instantiate and invoke all registered BeanFactoryPostProcessor beans,
 * respecting explicit order if given.
 * 
Must be called before singleton instantiation.
 */
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
	// Invoke BeanDefinitionRegistryPostProcessors first, if any.
	Set processedBeans = new HashSet();
	if (beanFactory instanceof BeanDefinitionRegistry) {
		BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
		List regularPostProcessors = new LinkedList();
		List registryPostProcessors =
				new LinkedList();
		for (BeanFactoryPostProcessor postProcessor : getBeanFactoryPostProcessors()) {
			if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
				BeanDefinitionRegistryPostProcessor registryPostProcessor =
						(BeanDefinitionRegistryPostProcessor) postProcessor;
				registryPostProcessor.postProcessBeanDefinitionRegistry(registry);
				registryPostProcessors.add(registryPostProcessor);
			}
			else {
				regularPostProcessors.add(postProcessor);
			}
		}
		Map beanMap =
				beanFactory.getBeansOfType(BeanDefinitionRegistryPostProcessor.class, true, false);
		List registryPostProcessorBeans =
				new ArrayList(beanMap.values());
		OrderComparator.sort(registryPostProcessorBeans);
		for (BeanDefinitionRegistryPostProcessor postProcessor : registryPostProcessorBeans) {
			postProcessor.postProcessBeanDefinitionRegistry(registry);
		}
		invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(registryPostProcessorBeans, beanFactory);
		invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		processedBeans.addAll(beanMap.keySet());
	}
	else {
		// Invoke factory processors registered with the context instance.
		invokeBeanFactoryPostProcessors(getBeanFactoryPostProcessors(), beanFactory);
	}

	// Do not initialize FactoryBeans here: We need to leave all regular beans
	// uninitialized to let the bean factory post-processors apply to them!
	String[] postProcessorNames =
			beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

	// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
	// Ordered, and the rest.
	List priorityOrderedPostProcessors = new ArrayList();
	List orderedPostProcessorNames = new ArrayList();
	List nonOrderedPostProcessorNames = new ArrayList();
	for (String ppName : postProcessorNames) {
		if (processedBeans.contains(ppName)) {
			// skip - already processed in first phase above
		}
		else if (isTypeMatch(ppName, PriorityOrdered.class)) {
			priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
		}
		else if (isTypeMatch(ppName, Ordered.class)) {
			orderedPostProcessorNames.add(ppName);
		}
		else {
			nonOrderedPostProcessorNames.add(ppName);
		}
	}

	// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
	OrderComparator.sort(priorityOrderedPostProcessors);
	invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

	// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
	List orderedPostProcessors = new ArrayList();
	for (String postProcessorName : orderedPostProcessorNames) {
		orderedPostProcessors.add(getBean(postProcessorName, BeanFactoryPostProcessor.class));
	}
	OrderComparator.sort(orderedPostProcessors);
	invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

	// Finally, invoke all other BeanFactoryPostProcessors.
	List nonOrderedPostProcessors = new ArrayList();
	for (String postProcessorName : nonOrderedPostProcessorNames) {
		nonOrderedPostProcessors.add(getBean(postProcessorName, BeanFactoryPostProcessor.class));
	}
	invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
}

registerBeanPostProcessors

         回调Context所有的BeanPostProcessor：

AbstractApplicationContext.java

/**
 * Instantiate and invoke all registered BeanPostProcessor beans,
 * respecting explicit order if given.
 * 
Must be called before any instantiation of application beans.
 */
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
	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 priorityOrderedPostProcessors = new ArrayList();
	List internalPostProcessors = new ArrayList();
	List orderedPostProcessorNames = new ArrayList();
	List nonOrderedPostProcessorNames = new ArrayList();
	for (String ppName : postProcessorNames) {
		if (isTypeMatch(ppName, PriorityOrdered.class)) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			priorityOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		else if (isTypeMatch(ppName, Ordered.class)) {
			orderedPostProcessorNames.add(ppName);
		}
		else {
			nonOrderedPostProcessorNames.add(ppName);
		}
	}

	// First, register the BeanPostProcessors that implement PriorityOrdered.
	OrderComparator.sort(priorityOrderedPostProcessors);
	registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

	// Next, register the BeanPostProcessors that implement Ordered.
	List orderedPostProcessors = new ArrayList();
	for (String ppName : orderedPostProcessorNames) {
		BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
		orderedPostProcessors.add(pp);
		if (pp instanceof MergedBeanDefinitionPostProcessor) {
			internalPostProcessors.add(pp);
		}
	}
	OrderComparator.sort(orderedPostProcessors);
	registerBeanPostProcessors(beanFactory, orderedPostProcessors);

	// Now, register all regular BeanPostProcessors.
	List nonOrderedPostProcessors = new ArrayList();
	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.
	OrderComparator.sort(internalPostProcessors);
	registerBeanPostProcessors(beanFactory, internalPostProcessors);

	beanFactory.addBeanPostProcessor(new ApplicationListenerDetector());
}

initMessageSource

       初始化messageSource，支持资源国际化：

AbstractApplicationContext.java

/**
 * 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 + "]");
		}
	}
}

initApplicationEventMulticaster

       初始化ApplicationEventMulticaster，用于发送ApplicationEvent：

AbstractApplicationContext.java

/**
 * 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 + "]");
		}
	}
}

onRefresh

AbstractRefreshableWebApplicationContext.java

/**
 * Initialize the theme capability.
 */
@Override
protected void onRefresh() {
	this.themeSource = UiApplicationContextUtils.initThemeSource(this);
}

registerListeners

       对ApplicationEventMulticaster注册ApplicationListener监听者：

AbstractApplicationContext.java

/**
 * 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 lisName : listenerBeanNames) {
		getApplicationEventMulticaster().addApplicationListenerBean(lisName);
	}
}

finishBeanFactoryInitialization

        实例化当前所有非懒加载的singleton：

AbstractApplicationContext.java

/**
 * 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));
	}

	// 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();
}

finishRefresh

      完成Context的refresh工作，发送相应的事件：

AbstractApplicationContext.java

/**
 * 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);
}