【SpringIOC容器初始化（一）】

【SpringIOC容器初始化（一）】 1、 IOC容器是指的spring bean 工厂里面MAP存储结构，包含beanFactory、applicationContext工厂； 2、 beanFactory采取的延迟加载,第一次getBean时才会初始化Bean； applicationContext是加载完applicationContext.xml 就创建了具体的bean实例(只对BeanDefition中描述是单例的bean,才进行恶汉模式创建) 3、applicationContext接口常用实现类 classpathXmlApplicationContext : 它是从类的跟路劲下加载配置文件,推荐使用这种 FileSystemXmlApplicationContext: 它是从磁盘上加载配置文件,配置文件可以在磁盘的任意位置 AnnotationConfigApplicationContext : 当我们使用注解配置容器对象时，需要使用此类来创建 spring 容器。它用来读取注解。 4、步骤 4.1 new ClassPathXmlApplicationContext(),初始化ClassPathXmlApplicationContext public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) throws BeansException { super(parent); setConfigLocations(configLocations); if (refresh) { refresh(); } } 4.2 调用AbstractRefreshableConfigApplicationContext的setConfigLocations(configLocations),设置xml文件路径 public void setConfigLocations(String... locations) { if (locations != null) { Assert.noNullElements(locations, "Config locations must not be null"); this.configLocations = new String[locations.length]; for (int i = 0; i < locations.length; i++) { this.configLocations[i] = resolvePath(locations[i]).trim(); } } else { this.configLocations = null; } } 4.3 AbstractXmlApplicationContext方法loadBeanDefinitions public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext { private boolean validating = true; public AbstractXmlApplicationContext() { } public AbstractXmlApplicationContext(ApplicationContext parent) { super(parent); } public void setValidating(boolean validating) { this.validating = validating; } protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException { // 这里最终还是通过XmlBeanDefinitionReader进行加载xml XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory); beanDefinitionReader.setEnvironment(this.getEnvironment()); beanDefinitionReader.setResourceLoader(this); beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this)); this.initBeanDefinitionReader(beanDefinitionReader); this.loadBeanDefinitions(beanDefinitionReader); } protected void initBeanDefinitionReader(XmlBeanDefinitionReader reader) { reader.setValidating(this.validating); } protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException { Resource[] configResources = this.getConfigResources(); // 获取配置文件路径的资源。 if (configResources != null) { reader.loadBeanDefinitions(configResources); // 这里调用了XmlBeanDefinitionReader的loadBeanDefinitions方法。这里将对xml进行解析，最终加入到map中 } String[] configLocations = this.getConfigLocations(); if (configLocations != null) { reader.loadBeanDefinitions(configLocations); } } protected Resource[] getConfigResources() { return null; } } 4.4 XmlBeanDefinitionReader 形成 private Class<?> documentReaderClass = DefaultBeanDefinitionDocumentReader.class; private NamespaceHandlerResolver namespaceHandlerResolver; private DocumentLoader documentLoader = new DefaultDocumentLoader(); private EntityResolver entityResolver; private ErrorHandler errorHandler = new SimpleSaxErrorHandler(logger); private final XmlValidationModeDetector validationModeDetector = new XmlValidationModeDetector(); private final ThreadLocal<Set<EncodedResource>> resourcesCurrentlyBeingLoaded =new NamedThreadLocal<Set<EncodedResource>>("XML bean definition resources currently being loaded"); public XmlBeanDefinitionReader(BeanDefinitionRegistry registry) { super(registry); // 将XmlBeanFactory进行保存 } @Override public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException { return loadBeanDefinitions(new EncodedResource(resource)); // 包装了一下 } // 返回发现bean的个数 public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException { Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get(); //尝试获取 if (currentResources == null) { // 如果没有，是刚初始化，就进行初始化 currentResources = new HashSet<EncodedResource>(4); // 默认空间大小为4 this.resourcesCurrentlyBeingLoaded.set(currentResources); } if (!currentResources.add(encodedResource)) { // 添加当前的资源文件到Set容器中 throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!"); } try { // 获得配置文件的输入流(将配置资源文件转换为流) InputStream inputStream = encodedResource.getResource().getInputStream(); try { InputSource inputSource = new InputSource(inputStream); // 包装了这个流，为Source if (encodedResource.getEncoding() != null) { // 是否编码。编码了就进行解码 inputSource.setEncoding(encodedResource.getEncoding()); } return doLoadBeanDefinitions(inputSource, encodedResource.getResource()); // 这里加载这个配置 } finally { inputStream.close(); } } catch (IOException ex) {。。。。 } finally { currentResources.remove(encodedResource); // if (currentResources.isEmpty()) { // 如果为空，则从ThreadLocal中移除 this.resourcesCurrentlyBeingLoaded.remove(); } } } public int loadBeanDefinitions(InputSource inputSource) throws BeanDefinitionStoreException { return loadBeanDefinitions(inputSource, "resource loaded through SAX InputSource"); } public int loadBeanDefinitions(InputSource inputSource, String resourceDescription) throws BeanDefinitionStoreException { return doLoadBeanDefinitions(inputSource, new DescriptiveResource(resourceDescription)); } //实际完成对xml进行载入的方法 protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException { try { // Document代表xml文档对象 Document doc = doLoadDocument(inputSource, resource); // 总之这里会返回一个Document return registerBeanDefinitions(doc, resource); // 将返回的Document注册 } catch (BeanDefinitionStoreException ex) { throw ex; …. catch (Throwable ex) { throw new BeanDefinitionStoreException(resource.getDescription(),"Unexpected om "); } } // 加载xml文件，返回Document。使用DefaultDocumentLoader的loadDocument方法，返回一个Document protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception { return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler, getValidationModeForResource(resource), isNamespaceAware()); } //使用DefaultNamespaceHandlerResolver 进行解析Document public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException { BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader(); // 用代理对象 int countBefore = getRegistry().getBeanDefinitionCount(); // 获取父类的BeanDefinitionRegistry（这里也就是IOC容器DefaultListableBeanFactory），然后调用getBeanDefinitionCount方法。获得注册之前的数量 documentReader.registerBeanDefinitions(doc, createReaderContext(resource));// 这里进行了解析和注入，DefaultBeanDefinitionDocumentReader中实现 return getRegistry().getBeanDefinitionCount() - countBefore; // 这里返回了数量 } protected BeanDefinitionDocumentReader createBeanDefinitionDocumentReader() { return BeanDefinitionDocumentReader.class.cast(BeanUtils.instantiateClass(this.documentReaderClass)); } public XmlReaderContext createReaderContext(Resource resource) { return new XmlReaderContext(resource, this.problemReporter, this.eventListener, this.sourceExtractor, this, getNamespaceHandlerResolver()); } public NamespaceHandlerResolver getNamespaceHandlerResolver() { // 单例模式获取 if (this.namespaceHandlerResolver == null) { this.namespaceHandlerResolver = createDefaultNamespaceHandlerResolver(); } return this.namespaceHandlerResolver; } protected NamespaceHandlerResolver createDefaultNamespaceHandlerResolver() { return new DefaultNamespaceHandlerResolver(getResourceLoader().getClassLoader()); } 4.5 AbstractRefreshableConfigApplicationContext 将配置文件进行保存 public void setConfigLocation(String location) { setConfigLocations(StringUtils.tokenizeToStringArray(location, CONFIG_LOCATION_DELIMITERS)); } public void setConfigLocations(String... locations) { // 将配置文件进行保存 if (locations != null) { Assert.noNullElements(locations, "Config locations must not be null"); this.configLocations = new String[locations.length]; for (int i = 0; i < locations.length; i++) { this.configLocations[i] = resolvePath(locations[i]).trim(); // 查找出真实的路径 } } else { this.configLocations = null; } } 4.6 AbstractRefreshableApplicationContext之BeanFactory的处理 @Override protected final void refreshBeanFactory() throws BeansException { if (hasBeanFactory()) { // 判断是否有BeanFactory destroyBeans(); // 如果有就销毁， closeBeanFactory();//并且关闭 } try { DefaultListableBeanFactory beanFactory = createBeanFactory(); // 创建新的BeanFactory beanFactory.setSerializationId(getId()); // 设置序列化 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); } } ... @Override protected void cancelRefresh(BeansException ex) { synchronized (this.beanFactoryMonitor) { if (this.beanFactory != null) this.beanFactory.setSerializationId(null); } super.cancelRefresh(ex); } 4.7 调用AbstractApplicationContext的refresh(),重点看，对于ClassPathXmlApplicationContext加载bean，只需了解它的obtainFreshBeanFactory方法。 @Override public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // 刷新上下文环境 prepareRefresh();

// 初始化BeanFactory，进行xml文件读取 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

// 对BeanFactory进行各种功能的填充 prepareBeanFactory(beanFactory);

try { // 子类覆盖方法做其他的处理 postProcessBeanFactory(beanFactory);

// 激活BeanFactory的处理器 invokeBeanFactoryPostProcessors(beanFactory);

// 注册拦截Bean创建的Bean处理器 registerBeanPostProcessors(beanFactory);

// 为上下文初始化Message源 initMessageSource();

// 初始化应用消息广播器 initApplicationEventMulticaster();

// 留给子类初始化其他的bean onRefresh();

// 查找Listeners bean,注册到消息广播器中 registerListeners();

// 初始化剩下的单实例 finishBeanFactoryInitialization(beanFactory);

// 完成刷新过程，通知生命周期处理器 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. destroyBeans();

// Reset 'active' flag. 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(); } } } 4.8 refresh中各个方法解析 protected void prepareRefresh() { this.startupDate = System.currentTimeMillis(); this.closed.set(false); this.active.set(true); initPropertySources(); // 初始化配置文件 getEnvironment().validateRequiredProperties(); this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>(); } .. protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { refreshBeanFactory(); // 这里对xml进行了解析，并且已经成功加入到map中了 ConfigurableListableBeanFactory beanFactory = getBeanFactory(); return beanFactory; // 最终返回这个bean，就是DefaultListableBeanFactory对象，加载了xml的工厂 } .. 子类实现： 　　1、在bean工厂自动装配的时候忽略一些接口。如：ServletContextAware、ServletConfigAware 　　2、注册WEB应用特定的域（scope）到bean工厂中，以便WebApplicationContext可以使用它们。比如"request", "session", "globalSession", "application"， 　　3、注册WEB应用特定的Environment bean到bean工厂中，以便WebApplicationContext可以使用它们。如："contextParameters", "contextAttributes" protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());//主要是在这里面调用了所有的BeanFactoryPostProcessor if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader())); } } protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) { PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this); } .. //初始化MessageSource接口的一个实现类。这个接口提供了消息处理功能。主要用于国际化/i18n。 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()); } } } 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); } } .. //为这个context初始化一个事件广播器（ApplicationEventMulticaster）。 protected void initApplicationEventMulticaster() { ConfigurableListableBeanFactory beanFactory = getBeanFactory(); if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {//’applicationEventMulticaster’ 检查是否给context配了一个ApplicationEventMulticaster实现类 this.applicationEventMulticaster =beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class); } else {//如果没有，就是用默认的实现类 SimpleApplicationEventMulticaster this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory); beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster); } } .. protected void onRefresh() throws BeansException { // 子类实现.在AbstractApplicationContext的子类中初始化其他特殊的bean。其实就是初始化ThemeSource接口的实例。这个方法需要在所有单例bean初始化之前调用。 // For subclasses: do nothing by default. } protected void registerListeners() {//注册应用的监听器。就是注册实现了ApplicationListener接口的监听器bean，这些监听器是注册到ApplicationEventMulticaster中的。这不会影响到其它监听器bean。在注册完以后，还会将其前期的事件发布给相匹配的监听器。 // 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... 至此，已经完成将监听器注册到ApplicationEventMulticaster中，下面将发布前期的事件给监听器。 Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents; this.earlyApplicationEvents = null; if (earlyEventsToProcess != null) { for (ApplicationEvent earlyEvent : earlyEventsToProcess) { getApplicationEventMulticaster().multicastEvent(earlyEvent); } } } //完成bean工厂的初始化工作。这一步非常复杂，也非常重要，涉及到了bean的创建。第二步中只是完成了BeanDefinition的定义、解析、处理、注册。但是还没有初始化bean实例。这一步将初始化所有非懒加载的单例bean。这一步将会重新在一篇新的笔记中介绍。 //对配置了lazy-init属性的Bean进行预实例化处理 protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) { // Initialize conversion service for this context. 为容器指定一个转换服务(ConversionService) 在对某些Bean属性进行转换时使用 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)); } // Register a default embedded value resolver if no bean post-processor // (such as a PropertyPlaceholderConfigurer bean) registered any before: // at this point, primarily for resolution in annotation attribute values. if (!beanFactory.hasEmbeddedValueResolver()) { beanFactory.addEmbeddedValueResolver(new StringValueResolver() { @Override public String resolveStringValue(String strVal) { return getEnvironment().resolvePlaceholders(strVal); } }); } // 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. //为了类型匹配，停止使用临时的类加载器 beanFactory.setTempClassLoader(null); // Allow for caching all bean definition metadata, not expecting further changes. /缓存容器中所有注册的BeanDefinition元数据，以防被修改 beanFactory.freezeConfiguration(); // Instantiate all remaining (non-lazy-init) singletons. //对配置了lazy-init属性的单态模式Bean进行预实例化处理 beanFactory.preInstantiateSingletons();//DefaultListableBeanFactory对配置lazy-init属性的单例bean预实例化 } ... //完成context的刷新。主要是调用LifecycleProcessor的onRefresh()方法，并且发布事件（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); } ... protected void resetCommonCaches() { ReflectionUtils.clearCache(); ResolvableType.clearCache(); CachedIntrospectionResults.clearClassLoader(getClassLoader()); }

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