第五章 spring-connet之核心方法refresh

時間 2019-11-12

標籤第五 spring connet 核心方法 refresh 欄目 Spring 简体版

原文原文鏈接

前言

refresh是ApplicationContext最核心的方法，若是你搞定了這個方法ApplicationContext的都搞定了。java

public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			prepareRefresh();

			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			prepareBeanFactory(beanFactory);

			try {
				postProcessBeanFactory(beanFactory);

				invokeBeanFactoryPostProcessors(beanFactory);

				registerBeanPostProcessors(beanFactory);

				initMessageSource();
				
				initApplicationEventMulticaster();
				
				onRefresh();
				
				registerListeners();
				
				finishBeanFactoryInitialization(beanFactory);
				
				finishRefresh();
			}catch (BeansException ex) {
				if (logger.isWarnEnabled()) {
					logger.warn("Exception encountered during context initialization - " +
							"cancelling refresh attempt: " + ex);
				}
				destroyBeans();
				cancelRefresh(ex);
				throw ex;
			}finally {
				resetCommonCaches();
			}
		}
}

prepareRefresh

申明與實現AbstractApplicationContext類中web

protected void prepareRefresh() {
		// 啓動時間
		this.startupDate = System.currentTimeMillis();
		// 是否出去關閉狀態
		this.closed.set(false);
		// 是不是活躍的，這個狀態很重要
		this.active.set(true);
		if (logger.isInfoEnabled()) {
			logger.info("Refreshing " + this);
		}
		initPropertySources();
		// 校驗配置
		getEnvironment().validateRequiredProperties();
		// 早期事件
		this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
	}

initPropertySources

initPropertySources 申明在 AbstractApplicationContext，分別由AbstractRefreshableWebApplicationContext和GenericWebApplicationContext重寫，你會方法只是把web的servletContext與servletConfig加入到配置裏面了，spring

protected void initPropertySources() {
// For subclasses: do nothing by default.
}

GenericWebApplicationContextapp

protected void initPropertySources() {
		ConfigurableEnvironment env = getEnvironment();
		if (env instanceof ConfigurableWebEnvironment) {
			((ConfigurableWebEnvironment) env).initPropertySources(this.servletContext, null);
		}
	}

AbstractRefreshableWebApplicationContextide

protected void initPropertySources() {
		ConfigurableEnvironment env = getEnvironment();
		if (env instanceof ConfigurableWebEnvironment) {
			((ConfigurableWebEnvironment) env).initPropertySources(this.servletContext, this.servletConfig);
		}
	}

obtainFreshBeanFactory

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

refreshBeanFactorypost

protected final void refreshBeanFactory() throws BeansException {
		if (hasBeanFactory()) {
			// 既然要refresh，那麼必須會失敗掉全部bean
			destroyBeans();
			// 關閉工廠
			closeBeanFactory();
		}
		try {
			// 建立bean，看過BeanFactory系列文章的同窗應該知道，會建立那個對象吧
			DefaultListableBeanFactory beanFactory = createBeanFactory();
			beanFactory.setSerializationId(getId());
			// customizeBeanFactory的內容請看 BeanFactory 系列的章節
			customizeBeanFactory(beanFactory);
			loadBeanDefinitions(beanFactory);
			synchronized (this.beanFactoryMonitor) {
				this.beanFactory = beanFactory;
			}
		}
		catch (IOException ex) {
			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
		}
}

loadBeanDefinitionsui

建立AnnotatedBeanDefinitionReader 與 ClassPathBeanDefinitionScanner 並加載對應class與 basePackages。注意若是不調用ApplicationContext的方法，是沒有class與basePackages的。spring默認掃描路徑不在這裏this

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) {
		AnnotatedBeanDefinitionReader reader = getAnnotatedBeanDefinitionReader(beanFactory);
		ClassPathBeanDefinitionScanner scanner = getClassPathBeanDefinitionScanner(beanFactory);

		BeanNameGenerator beanNameGenerator = getBeanNameGenerator();
		if (beanNameGenerator != null) {
			reader.setBeanNameGenerator(beanNameGenerator);
			scanner.setBeanNameGenerator(beanNameGenerator);
			beanFactory.registerSingleton(AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR, beanNameGenerator);
		}

		ScopeMetadataResolver scopeMetadataResolver = getScopeMetadataResolver();
		if (scopeMetadataResolver != null) {
			reader.setScopeMetadataResolver(scopeMetadataResolver);
			scanner.setScopeMetadataResolver(scopeMetadataResolver);
		}

		if (!this.annotatedClasses.isEmpty()) {
			if (logger.isInfoEnabled()) {
				logger.info("Registering annotated classes: [" +
						StringUtils.collectionToCommaDelimitedString(this.annotatedClasses) + "]");
			}
			reader.register(ClassUtils.toClassArray(this.annotatedClasses));
		}

		if (!this.basePackages.isEmpty()) {
			if (logger.isInfoEnabled()) {
				logger.info("Scanning base packages: [" +
						StringUtils.collectionToCommaDelimitedString(this.basePackages) + "]");
			}
			scanner.scan(StringUtils.toStringArray(this.basePackages));
		}

		String[] configLocations = getConfigLocations();
		if (configLocations != null) {
			for (String configLocation : configLocations) {
				try {
					Class<?> clazz = getClassLoader().loadClass(configLocation);
					if (logger.isInfoEnabled()) {
						logger.info("Successfully resolved class for [" + configLocation + "]");
					}
					reader.register(clazz);
				}
				catch (ClassNotFoundException ex) {
					if (logger.isDebugEnabled()) {
						logger.debug("Could not load class for config location [" + configLocation +
								"] - trying package scan. " + ex);
					}
					int count = scanner.scan(configLocation);
					if (logger.isInfoEnabled()) {
						if (count == 0) {
							logger.info("No annotated classes found for specified class/package [" + configLocation + "]");
						}
						else {
							logger.info("Found " + count + " annotated classes in package [" + configLocation + "]");
						}
					}
				}
			}
		}
	}

prepareBeanFactory

在BeanFactory加入一些bean，或者一些規則debug

*/
	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));
		// 下面是忽視依賴關係，自動忽視下面對象的依賴，
		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());
		}
	}

postProcessBeanFactory

這是子類AnnotationConfigReactiveWebServerApplicationContext重寫了父類的方法，因此postProcessBeanFactory做用是爲子類提供本身行爲而設計的。其功能與prepareBeanFactory如出一轍。只是面對的對象不同。設計

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

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()));
		}
	}

registerBeanPostProcessors

從 BeanFactory 獲得BeanPostProcessors與子接口的實現類。進行排序，而後加到beanFactory的BeanPostProcessor集合中，方面後續操做。功能能夠在上面方法執行爲了保證單一性，重複執行了一次。

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
	}

initMessageSource

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

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

protected void onRefresh() {
		this.themeSource = UiApplicationContextUtils.initThemeSource(this);
	}

registerListeners

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);
			}
		}
	}

finishBeanFactoryInitialization

finish beanfactory.由於不一樣功能的容器，在啓動成功以後，須要多factory進行不一樣的操做。

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
		// 若是存在conversion 服務，從beanFactory工廠獲得並set到beanFctory
		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));
		}

		if (!beanFactory.hasEmbeddedValueResolver()) {
			beanFactory.addEmbeddedValueResolver(new StringValueResolver() {
				@Override
				public String resolveStringValue(String strVal) {
					return getEnvironment().resolvePlaceholders(strVal);
				}
			});
		}

		// 一個比較雞肋的功能
		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

refresh成功的處理

protected void finishRefresh() {
		// 初始化ApplicationContext生命週期
		initLifecycleProcessor();

		// 執行生命週期onRefresh
		getLifecycleProcessor().onRefresh();

		// 執行CntextRefreshed事件
		publishEvent(new ContextRefreshedEvent(this));

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

總結

prepareRefresh讓ApplicationContext作一些準備
obtainFreshBeanFactory由子類解決使用什麼BeanFactory，讓一些子類本身的處理BeanFactory的事情
prepareBeanFactory是 AbstractApplicationContext規範BeanFactory統一的行爲
invokeBeanFactoryPostProcessors 執行BeanPostProcessors
registerBeanPostProcessors 對BeanPostProcessors 排序，並加入beanFactory。接下來就是對ApplicationContext行爲初始化與執行
initMessageSource 初始化MessageSource
initApplicationEventMulticaster 初始化ApplicationEventMulticaster
onRefresh 無用
registerListeners 執行事件
finishBeanFactoryInitialization 對beanFactory進行整理工做
finishRefresh