Spring容器创建流程（2）创建beanFactory，加载BeanDefinition

Spring 容器的创建。obtainFreshBeanFactorr()中完成容器的创建。（BeanFactory关系类图，之前的执行流程可在本系列博客中看到）。接下来看容器创建的第二部，创建beanFactory

容器refresh总览：

     synchronized (this.startupShutdownMonitor) {// 设置环境，校验参数。prepareRefresh();// 创建BeanFactory（DefaultListableBeanFactor），加载bean定义信息。ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();// Prepare the bean factory for use in this context.prepareBeanFactory(beanFactory);try {// Allows post-processing of the bean factory in context subclasses.postProcessBeanFactory(beanFactory);// Invoke factory processors registered as beans in the context.invokeBeanFactoryPostProcessors(beanFactory);// Register bean processors that intercept bean creation.registerBeanPostProcessors(beanFactory);// Initialize message source for this context.initMessageSource();// Initialize event multicaster for this context.initApplicationEventMulticaster();// Initialize other special beans in specific context subclasses.onRefresh();// Check for listener beans and register them.registerListeners();// Instantiate all remaining (non-lazy-init) singletons.finishBeanFactoryInitialization(beanFactory);// Last step: publish corresponding event.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();}}

obtainFreshBeanFactory 容器创建

容器初始化refresh方法中 obtainFreshBeanFactory用来创建容器实例

// AbstractApplicationContext中，重要的方法是refreshBeanFactory()方法
// getBeanFactory()不过是直接获取创建好的工厂protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {refreshBeanFactory();ConfigurableListableBeanFactory beanFactory = getBeanFactory();if (logger.isDebugEnabled()) {logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);}return beanFactory;}

refreshBeanFactory()

refreshBeanFactory 方法在 AbstractApplicationContext的子类AbstractRefreshableApplicationContext中实现。

BeanDefinition：是包含着类的定义信息，类的名字，作用域，是否懒加载等等描述bean的信息（也就是xml中配置的bean信息的封装）

 @Overrideprotected final void refreshBeanFactory() throws BeansException {// 如果工厂已经创建，销毁工厂if (hasBeanFactory()) {destroyBeans();closeBeanFactory();}try {// 直接创建一个DefaultListableBeanFactory工厂DefaultListableBeanFactory beanFactory = createBeanFactory();beanFactory.setSerializationId(getId());// 交给子类自定义配置customizeBeanFactory(beanFactory);// 加载beanDefinitionloadBeanDefinitions(beanFactory);synchronized (this.beanFactoryMonitor) {this.beanFactory = beanFactory;}}catch (IOException ex) {throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);}}

AbstractRefreshableApplicationContext 中对 customizeBeanFactory的实现

 protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {// 是否允许bean定义覆盖（默认不允许）if (this.allowBeanDefinitionOverriding != null) {beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);}// 是否允许循环依赖（默认不允许）if (this.allowCircularReferences != null) {beanFactory.setAllowCircularReferences(this.allowCircularReferences);}}

loadBeanDefinitions(beanFactory);

创建工厂中最重要的一步，加载bean的定义信息。

首先明确几个概念

XXXResource：代表着资源文件
XXXBeanDefinitionReader: 用于读取Resource,
BeanDefinition: bean的描述信息，也就是xml中bean配置的描述的封装

 @Overrideprotected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {// beanFactory本身是一个BeanDefinitionRegistry，用于注册bean信息// 创建 reader 读取 resourceXmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);// 设置资源加载环境beanDefinitionReader.setEnvironment(this.getEnvironment());// 设置资源加载器，beanFactory也实现了ResourceLoader,用于将制定位置的资源，加载为ResourcebeanDefinitionReader.setResourceLoader(this);beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));// 给子类一个再次设置的机会initBeanDefinitionReader(beanDefinitionReader);// 加载bean定义信息loadBeanDefinitions(beanDefinitionReader);}protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {Resource[] configResources = getConfigResources();if (configResources != null) {reader.loadBeanDefinitions(configResources);}// 获取资源文件路径String[] configLocations = getConfigLocations();if (configLocations != null) {// 使用XmlBeanDefinitionReader加载资源reader.loadBeanDefinitions(configLocations);}}

XmlBeanDefinitionReader 加载 Resource

 @Overridepublic int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {Assert.notNull(locations, "Location array must not be null");int counter = 0;for (String location : locations) {counter += loadBeanDefinitions(location);}return counter;}@Overridepublic int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {return loadBeanDefinitions(location, null);}// 最终调用这个方法public int loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources) throws BeanDefinitionStoreException {// 获取资源加载器，也就是前面注册的beanFactory(它就是一个资源加载器这里用的是ClassPathXmlApplicationContext)ResourceLoader resourceLoader = getResourceLoader();if (resourceLoader == null) {throw new BeanDefinitionStoreException("Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");}if (resourceLoader instanceof ResourcePatternResolver) {// Resource pattern matching available.try {// 加载资源Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);// 加载bean定义信息int loadCount = loadBeanDefinitions(resources);if (actualResources != null) {for (Resource resource : resources) {actualResources.add(resource);}}if (logger.isDebugEnabled()) {logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");}return loadCount;}catch (IOException ex) {throw new BeanDefinitionStoreException("Could not resolve bean definition resource pattern [" + location + "]", ex);}}else {// Can only load single resources by absolute URL.Resource resource = resourceLoader.getResource(location);int loadCount = loadBeanDefinitions(resource);if (actualResources != null) {actualResources.add(resource);}if (logger.isDebugEnabled()) {logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");}return loadCount;}}

Resource[] resources ((ResourcePatternResolver)resourceLoader).getResources(location);

// this.resourcePatternResolver 在构造器中已经初始化完成。@Overridepublic Resource[] getResources(String locationPattern) throws IOException {return this.resourcePatternResolver.getResources(locationPattern);}

PathMarchingResourcePatternResolver获取资源

 @Overridepublic Resource[] getResources(String locationPattern) throws IOException {Assert.notNull(locationPattern, "Location pattern must not be null");// 如果以 classpath*:开头if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {// a class path resource (multiple resources for same name possible)// isPattern判断资源路径中是否包含* 或者 ？if (getPathMatcher().isPattern(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()))) {// a class path resource patternreturn findPathMatchingResources(locationPattern);}else {// all class path resources with the given namereturn findAllClassPathResources(locationPattern.substring(CLASSPATH_ALL_URL_PREFIX.length()));}}else {// Generally only look for a pattern after a prefix here,// and on Tomcat only after the "*/" separator for its "war:" protocol.int prefixEnd = (locationPattern.startsWith("war:") ? locationPattern.indexOf("*/") + 1 :locationPattern.indexOf(':') + 1);if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {// a file patternreturn findPathMatchingResources(locationPattern);}else {// a single resource with the given name// 提供的资源路径是 classpath:application.xml 最终调用这里。// 路径封装为一个Resourcereturn new Resource[] {getResourceLoader().getResource(locationPattern)};}}}

XmlBeanDefinitionReader 加载 Resource 已经完成，接下来就是使用Resource加载BeanDefinition。

XmlBeanDefinitionReader 加载BeanDefinition

AbstractBeanDefinitionReader.loadBeanDefinitions(String location, @Nullable Set actualResources) 方法中，getConfigResources（）已经获取资源完毕。

// 加载资源
Resource[] configResources = getConfigResources();
// 加载bean定义信息
int loadCount = loadBeanDefinitions(resources);

 @Overridepublic int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {Assert.notNull(resources, "Resource array must not be null");int counter = 0;for (Resource resource : resources) {counter += loadBeanDefinitions(resource);}return counter;}@Overridepublic int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {// 统一编码封装return loadBeanDefinitions(new EncodedResource(resource));}public int loadBeanDefinitions(EncodedResource encodedResource) throws   BeanDefinitionStoreException {Assert.notNull(encodedResource, "EncodedResource must not be null");if (logger.isInfoEnabled()) {logger.info("Loading XML bean definitions from " + encodedResource.getResource());}
// resourceCurrentlyBeingLoaded是一个ThreadLocal,存放线程开始加载的资源Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();if (currentResources == null) {currentResources = new HashSet<>(4);this.resourcesCurrentlyBeingLoaded.set(currentResources);}if (!currentResources.add(encodedResource)) {throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!");}try {// 获取resource流InputStream inputStream = encodedResource.getResource().getInputStream();try {// 包装为InputSourceInputSource inputSource = new InputSource(inputStream);if (encodedResource.getEncoding() != null) {inputSource.setEncoding(encodedResource.getEncoding());}// 加载bean定义信息return doLoadBeanDefinitions(inputSource, encodedResource.getResource());}finally {inputStream.close();}}catch (IOException ex) {throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), ex);}finally {currentResources.remove(encodedResource);if (currentResources.isEmpty()) {this.resourcesCurrentlyBeingLoaded.remove();}}}

 protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)throws BeanDefinitionStoreException {try {// 使用dom解析文件Document doc = doLoadDocument(inputSource, resource);// 解析dom包装为beanDefinition，具体的解析过程比较复杂。// beanDefinitionRegistry就是上面的beanFactory,解析dom封装为beanDefinition后，保存到beanFactory中（就是调用beanDefinitionRegistry的registerBeanDefinition()方法）return registerBeanDefinitions(doc, resource);}....}

自此，beanFactory创建完成并且，beanDefinition也加载完成。