Spring源码之XMLBeanFactory-白红宇

本文是针对Srping的XMLBeanFactory来进行解析xml并将解析后的信息使用GenericBeanDefinition作为载体进行注册,xmlBeanFactory已经在Spring 3.1中被标记为不建议使用，但是我们分析源码不影响，因为源码并未改变，并ApplicationContext依旧使用XmlBeanDefinitionReader和DefaultListableBeanFactory进行xml的解析和注册工作，本篇博客是跟源码一步步看spring怎么实现bean的注册，源码为spring5.X,源码已经在每一行上加了注释，方便读者学习。

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首先我们从XMLBeanFactory入手,直接上代码：

package org.springframework.lantao;import org.springframework.beans.factory.BeanFactory;import org.springframework.beans.factory.xml.XmlBeanFactory;import org.springframework.core.io.ClassPathResource;public class XmlBeanFactoryTest {    public static void main(String[] args) {        // 资源加载        ClassPathResource classPathResource = new ClassPathResource("spring-bean.xml");        // XmlBeanFactory 加载资源并解析注册bean        BeanFactory beanFactory = new XmlBeanFactory(classPathResource);        // BeanFactory.getBean();        UserBean userBean = (UserBean) beanFactory.getBean("userBean");        System.out.println(userBean.getName());	}}复制代码

XmlBeanFactory解析Xml是使用了XmlBeanDefinitionReader.loadBeanDefinition()方法,源码如下：

@Deprecated@SuppressWarnings({
    "serial", "all"})public class XmlBeanFactory extends DefaultListableBeanFactory {	private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);	/**	 * Create a new XmlBeanFactory with the given resource,	 * which must be parsable using DOM.	 * @param resource the XML resource to load bean definitions from	 * @throws BeansException in case of loading or parsing errors	 */	public XmlBeanFactory(Resource resource) throws BeansException {		//调用构造方法  79行		this(resource, null);	}	/**	 * Create a new XmlBeanFactory with the given input stream,	 * which must be parsable using DOM.	 * @param resource the XML resource to load bean definitions from	 * @param parentBeanFactory parent bean factory	 * @throws BeansException in case of loading or parsing errors	 */	public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {		//ignoreDependencyInterface 忽略自动装配		//主要功能就是当有忽略的接口类，自动装配会忽略这部分类的初始化装配，因为某种情况下，此时的接口实现类不能初始化，列如BeanNameAware,要想装配这个接口的实现对象，可以实现这个接口。		super(parentBeanFactory);		//这段代码是真正的资源加载		this.reader.loadBeanDefinitions(resource);	}}复制代码

我们直接看loadBeanDefinition方法，源码：

/**	 * Load bean definitions from the specified XML file.	 * @param resource the resource descriptor for the XML file	 * @return the number of bean definitions found	 * @throws BeanDefinitionStoreException in case of loading or parsing errors	 */	@Override	public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {		// 对EncodedResource进行封装，设置String encoding, Charset charset		return loadBeanDefinitions(new EncodedResource(resource));	}	/**	 * Load bean definitions from the specified XML file.	 * @param encodedResource the resource descriptor for the XML file,	 * allowing to specify an encoding to use for parsing the file	 * @return the number of bean definitions found	 * @throws BeanDefinitionStoreException in case of loading or parsing errors	 */	public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {		//encodedResource 不可以为空		Assert.notNull(encodedResource, "EncodedResource must not be null");		if (logger.isTraceEnabled()) {			logger.trace("Loading XML bean definitions from " + encodedResource);		}		// 通过属性来记录已经加载的资源		Set
     
       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 {			// 从encodedResource已经封装的Resource获取InputStream			InputStream inputStream = encodedResource.getResource().getInputStream();			try {				//InputSource 并不是spring的，而是 org.xml.sax				InputSource inputSource = new InputSource(inputStream);				//如果encodedResource 中的 Encoding 不是 null 则同步设置 InputSource的 Encoding				if (encodedResource.getEncoding() != null) {					inputSource.setEncoding(encodedResource.getEncoding());				}				//加载bean的Definitions 将xml中的信息加载到Definition中，并且在内存中注册的也是key+definitions				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();			}		}	}复制代码

上述源码可能看着比较长,但实际上这里并不是真正解析的地方，在这里做了如下：

1:从encodedResource已经封装的Resource获取InputStream；

2:如果encodedResource 中的 Encoding 不是 null 则同步设置 InputSource的 Encoding；

3:将解析动作委托给doLoadBeanDefinitions实现；

接下来我们继续看doLoadBeanDefinitions方法内容：

/**	 * Actually load bean definitions from the specified XML file.	 * @param inputSource the SAX InputSource to read from	 * @param resource the resource descriptor for the XML file	 * @return the number of bean definitions found	 * @throws BeanDefinitionStoreException in case of loading or parsing errors	 * @see #doLoadDocument	 * @see #registerBeanDefinitions	 */	protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)			throws BeanDefinitionStoreException {		try {			//加载 Document			Document doc = doLoadDocument(inputSource, resource);			//注册 bean			int count = registerBeanDefinitions(doc, resource);			if (logger.isDebugEnabled()) {				logger.debug("Loaded " + count + " bean definitions from " + resource);			}			return count;		}		catch (BeanDefinitionStoreException ex) {			throw ex;		}		catch (SAXParseException ex) {			throw new XmlBeanDefinitionStoreException(resource.getDescription(),					"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);		}		catch (SAXException ex) {			throw new XmlBeanDefinitionStoreException(resource.getDescription(),					"XML document from " + resource + " is invalid", ex);		}		catch (ParserConfigurationException ex) {			throw new BeanDefinitionStoreException(resource.getDescription(),					"Parser configuration exception parsing XML from " + resource, ex);		}		catch (IOException ex) {			throw new BeanDefinitionStoreException(resource.getDescription(),					"IOException parsing XML document from " + resource, ex);		}		catch (Throwable ex) {			throw new BeanDefinitionStoreException(resource.getDescription(),					"Unexpected exception parsing XML document from " + resource, ex);		}	}复制代码

当我们看着这个方法的时候，依旧不是真正的解析或注册的方法，在这里只是做了Document的加载，并将后续工作委托给了registerBeanDefinitions,registerBeanDefinitions方法的返回时注册Bean的个数；

我们继续看registerBeanDefinitions的源码：

/**	 * Register the bean definitions contained in the given DOM document.	 * Called by {@code loadBeanDefinitions}.	 * Creates a new instance of the parser class and invokes	 * {@code registerBeanDefinitions} on it.	 * @param doc the DOM document	 * @param resource the resource descriptor (for context information)	 * @return the number of bean definitions found	 * @throws BeanDefinitionStoreException in case of parsing errors	 * @see #loadBeanDefinitions	 * @see #setDocumentReaderClass	 * @see BeanDefinitionDocumentReader#registerBeanDefinitions	 */	public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {		//实例化 BeanDefinitionDocumentReader		BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();		//获取之前的beanDefinition加载个数		int countBefore = getRegistry().getBeanDefinitionCount();		//加载xml及注册bean		documentReader.registerBeanDefinitions(doc, createReaderContext(resource));		//记录本次加载个数		return getRegistry().getBeanDefinitionCount() - countBefore;	}复制代码

在registerBeanDefinitions方法具体实现：

1：通过BeanUtils.instantiateClass(this.documentReaderClass)的方法实例化BeanDefinitionDocumentReader；

2：通过DefaultListAbleBeanFactory中的beanDefinitionMap.size()获取之前注册bean的个数，（beanDefinitionMap是存储最终的xml解析后信息的载体，xml解析后信息是由GenericBeanDefinition进行存储，beanDefinitionMap的存储格式是key:String value:GenericBeanDefinition）

3:将解析xml和注册的工作委托给BeanDefinitionDocumentReader的registerBeanDefinitions方法；

4：记录本次加载个数并返回；

继续看BeanDefinitionDocumentReader的registerBeanDefinitions方法：

/**	 * This implementation parses bean definitions according to the "spring-beans" XSD	 * (or DTD, historically).	 * Opens a DOM Document; then initializes the default settings	 * specified at the {@code 
      } level; then parses the contained bean definitions.	 */	@Override	public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {		//实例化 ReaderContext		this.readerContext = readerContext;		//注册		doRegisterBeanDefinitions(doc.getDocumentElement());	}复制代码

registerBeanDefinitions并没有做什么，我们继续看doRegisterBeanDefinitions方法：

/**	 * Register each bean definition within the given root {@code 
     } element.	 */	@SuppressWarnings("deprecation")  // for Environment.acceptsProfiles(String...)	protected void doRegisterBeanDefinitions(Element root) {		// Any nested 
     
       elements will cause recursion in this method. In		// order to propagate and preserve 
      
        default-* attributes correctly,		// keep track of the current (parent) delegate, which may be null. Create		// the new (child) delegate with a reference to the parent for fallback purposes,		// then ultimately reset this.delegate back to its original (parent) reference.		// this behavior emulates a stack of delegates without actually necessitating one.		BeanDefinitionParserDelegate parent = this.delegate;		this.delegate = createDelegate(getReaderContext(), root, parent);		//验证xml namespace, BeanDefinitionParserDelegate.BEANS_NAMESPACE_URI		if (this.delegate.isDefaultNamespace(root)) {			//获取Attribute			String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);			if (StringUtils.hasText(profileSpec)) {				String[] specifiedProfiles = StringUtils.tokenizeToStringArray(						profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);				// We cannot use Profiles.of(...) since profile expressions are not supported				// in XML config. See SPR-12458 for details.				if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {					if (logger.isDebugEnabled()) {						logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec +								"] not matching: " + getReaderContext().getResource());					}					return;				}			}		}		//解析前处理， 内容null 留个子类实现		preProcessXml(root);		//解析		parseBeanDefinitions(root, this.delegate);		//解析后处理， 内容null 留个子类实现		postProcessXml(root);		this.delegate = parent;	}复制代码

在doRegisterBeanDefinitions烦那个发中验证xml的namespace,最重要的方法是parseBeanDefinitions，parseBeanDefinitions方法进行了解析操作；

parseBeanDefinitions方法的源码：

/**	 * Parse the elements at the root level in the document:	 * "import", "alias", "bean".	 * @param root the DOM root element of the document	 */	protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {		//验证xml namespace, BeanDefinitionParserDelegate.BEANS_NAMESPACE_URI		if (delegate.isDefaultNamespace(root)) {			NodeList nl = root.getChildNodes();			for (int i = 0; i < nl.getLength(); i++) {				Node node = nl.item(i);				if (node instanceof Element) {					Element ele = (Element) node;					if (delegate.isDefaultNamespace(ele)) {						//对默认标签处理						parseDefaultElement(ele, delegate);					}					else {						//对自定义标签处理						delegate.parseCustomElement(ele);					}				}			}		}		else {			//对自定义标签处理			delegate.parseCustomElement(root);		}	}复制代码

parseBeanDefinitions方法中已经开始对标签进行解析，区分默认标签和自定义标签，我们本次只对默认标签的源码进行解析，自定义标签自行DeBug，

parseDefaultElement方法的源码：

private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {		//解析import标签		if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {			importBeanDefinitionResource(ele);		}		//解析alias标签并注册		else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {			processAliasRegistration(ele);		}		//解析bean标签并注册		else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {			processBeanDefinition(ele, delegate);		}		//解析beans标签		else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {			// recurse			doRegisterBeanDefinitions(ele);		}	}复制代码

到这里我们可以看到，spring对import/bean/alias/beans的解析过程，对于beans的解析无法就是解析beans中的bean标签，spring直接又重新调用了doRegisterBeanDefinitions方法，我们接下来进行对bean标签的解析；

processBeanDefinition方法：

/**	 * Process the given bean element, parsing the bean definition	 * and registering it with the registry.	 */	protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {		//委托BeanDefinitionParserDelegate的parseBeanDefinitionElement方法进行元素解析并返回		//BeanDefinitionHolder实例，BeanDefinitionHolder已经包含了配置文件中的各种属性		BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);		//当BeanDefinitionHolder返回不null的情况，弱存在默认标签下的子标签再有自定义的属性，还需要再次解析		if (bdHolder != null) {			//解析默认标签中的自定义标签			bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);			try {				// Register the final decorated instance.				// 进行实例注册注册操作是BeanDefinitionReaderUtisl.registerBeanDefinition进行处理				BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());			}			catch (BeanDefinitionStoreException ex) {				getReaderContext().error("Failed to register bean definition with name '" +						bdHolder.getBeanName() + "'", ele, ex);			}			// Send registration event.			getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));		}	}复制代码

在processBeanDefinition方法中，spring做了两件事情：

1：委托BeanDefinitionParserDelegate的parseBeanDefinitionElement方法进行元素解析并返回BeanDefinitionHolder实例，BeanDefinitionHolder已经包含了配置文件中的各种属性

2：通过上获得的BeanDefinitionHolder进行bean的注册操作，通BeanDefinitionReaderUtils.registerBeanDefinition方法；

通过delegate.parseBeanDefinitionElement方法进行xml解析：

/**	 * Parses the supplied {@code 
     
      } element. May return {@code null}	 * if there were errors during parse. Errors are reported to the	 * {@link org.springframework.beans.factory.parsing.ProblemReporter}.	 */	@Nullable	public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) {		//解析id属性		String id = ele.getAttribute(ID_ATTRIBUTE);		//解析name属性		String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);		//分割name属性		List
      
        aliases = new ArrayList<>();		if (StringUtils.hasLength(nameAttr)) {			String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);			aliases.addAll(Arrays.asList(nameArr));		}		String beanName = id;		if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {			beanName = aliases.remove(0);			if (logger.isTraceEnabled()) {				logger.trace("No XML 'id' specified - using '" + beanName +						"' as bean name and " + aliases + " as aliases");			}		}		if (containingBean == null) {			checkNameUniqueness(beanName, aliases, ele);		}		//将信息封装到 beanDefinition中		AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);		if (beanDefinition != null) {			if (!StringUtils.hasText(beanName)) {				try {					//beanname不存在则使用默认规则创建					if (containingBean != null) {						beanName = BeanDefinitionReaderUtils.generateBeanName(								beanDefinition, this.readerContext.getRegistry(), true);					}					else {						beanName = this.readerContext.generateBeanName(beanDefinition);						// Register an alias for the plain bean class name, if still possible,						// if the generator returned the class name plus a suffix.						// This is expected for Spring 1.2/2.0 backwards compatibility.						String beanClassName = beanDefinition.getBeanClassName();						if (beanClassName != null &&								beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&								!this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {							aliases.add(beanClassName);						}					}					if (logger.isTraceEnabled()) {						logger.trace("Neither XML 'id' nor 'name' specified - " +								"using generated bean name [" + beanName + "]");					}				}				catch (Exception ex) {					error(ex.getMessage(), ele);					return null;				}			}			String[] aliasesArray = StringUtils.toStringArray(aliases);			return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);		}		return null;	}复制代码

在parseBeanDefinitionElement方法中做了三件事：

1：解析id/name；

2：检查name的唯一性；

3：将信息封装到 beanDefinition中，接下来直接看parseBeanDefinitionElement方法；

parseBeanDefinitionElement源码：

/**	 * Parse the bean definition itself, without regard to name or aliases. May return	 * {@code null} if problems occurred during the parsing of the bean definition.	 */	@Nullable	public AbstractBeanDefinition parseBeanDefinitionElement(			Element ele, String beanName, @Nullable BeanDefinition containingBean) {		this.parseState.push(new BeanEntry(beanName));		String className = null;		//解析classname属性		if (ele.hasAttribute(CLASS_ATTRIBUTE)) {			className = ele.getAttribute(CLASS_ATTRIBUTE).trim();		}		String parent = null;		//解析parent属性		if (ele.hasAttribute(PARENT_ATTRIBUTE)) {			parent = ele.getAttribute(PARENT_ATTRIBUTE);		}		try {			//创建用于承载属性的AbstractBeanDefinition类型的			AbstractBeanDefinition bd = createBeanDefinition(className, parent);			//解析bean的各种属性			parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);			//提取description			bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));			//解析meta （元数据）			parseMetaElements(ele, bd);			//解析Lookup-method 书中53页有使用方法			parseLookupOverrideSubElements(ele, bd.getMethodOverrides());			//解析replaced-method 书中55页有使用方法			parseReplacedMethodSubElements(ele, bd.getMethodOverrides());			//构造函数 参数			//解析constructor-arg 书中replaced-method后边			parseConstructorArgElements(ele, bd);			//解析Property 书中replaced-method后边			parsePropertyElements(ele, bd);			//解析Qualifier 书中Property后边			parseQualifierElements(ele, bd);			bd.setResource(this.readerContext.getResource());			bd.setSource(extractSource(ele));			return bd;		}		catch (ClassNotFoundException ex) {			error("Bean class [" + className + "] not found", ele, ex);		}		catch (NoClassDefFoundError err) {			error("Class that bean class [" + className + "] depends on not found", ele, err);		}		catch (Throwable ex) {			error("Unexpected failure during bean definition parsing", ele, ex);		}		finally {			this.parseState.pop();		}		return null;	}复制代码

通过上述代码我们可以看到这里首先是实例化了一个AbstractBeanDefinition来承载各种xml属性，接下来通过parseBeanDefinitionAttributes方法解析了xml中的各种你属性值，然后在解析(方法注入)，replaced-method(替换方法或方法返回值)，构造函数参数constructor-arg，property属性，Qualifier属性等；上述方法的源码就不一一展示了，无非都是通过Element进行解析；

接下来看真正注册的代码 BeanDefinitionReaderUtils.registerBeanDefinition

@Override	public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)			throws BeanDefinitionStoreException {		//beanName不可为空		Assert.hasText(beanName, "Bean name must not be empty");		//beanDefinition不可为空		Assert.notNull(beanDefinition, "BeanDefinition must not be null");		if (beanDefinition instanceof AbstractBeanDefinition) {			try {				//校验 MethodOverrides，MethodOverrides在解析并组装beanDefinition时有提到				((AbstractBeanDefinition) beanDefinition).validate();			}			catch (BeanDefinitionValidationException ex) {				throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,						"Validation of bean definition failed", ex);			}		}		//beanDefinitionMap 存储实例的全局Map 使用ConcurrentHashMap 线程安全		BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);		//如果已经注册 处理内容		if (existingDefinition != null) {			//是否覆盖			if (!isAllowBeanDefinitionOverriding()) {				throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);			}			else if (existingDefinition.getRole() < beanDefinition.getRole()) {				// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE				if (logger.isInfoEnabled()) {					logger.info("Overriding user-defined bean definition for bean '" + beanName +							"' with a framework-generated bean definition: replacing [" +							existingDefinition + "] with [" + beanDefinition + "]");				}			}			else if (!beanDefinition.equals(existingDefinition)) {				if (logger.isDebugEnabled()) {					logger.debug("Overriding bean definition for bean '" + beanName +							"' with a different definition: replacing [" + existingDefinition +							"] with [" + beanDefinition + "]");				}			}			else {				if (logger.isTraceEnabled()) {					logger.trace("Overriding bean definition for bean '" + beanName +							"' with an equivalent definition: replacing [" + existingDefinition +							"] with [" + beanDefinition + "]");				}			}			this.beanDefinitionMap.put(beanName, beanDefinition);		}		else {			//判断是否已经至少创建过一次 使用AbstractBeanFactory.alreadyCreated来判断			if (hasBeanCreationStarted()) {				// Cannot modify startup-time collection elements anymore (for stable iteration)				synchronized (this.beanDefinitionMap) {					this.beanDefinitionMap.put(beanName, beanDefinition);					List
     
       updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);					updatedDefinitions.addAll(this.beanDefinitionNames);					updatedDefinitions.add(beanName);					this.beanDefinitionNames = updatedDefinitions;					if (this.manualSingletonNames.contains(beanName)) {						Set
      
        updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);						updatedSingletons.remove(beanName);						this.manualSingletonNames = updatedSingletons;					}				}			}			else {				// 仍处于启动注册阶段				// 注册 beanDefinitionMap 新实例 beanName + beanDefinition				this.beanDefinitionMap.put(beanName, beanDefinition);				// 增加beanDefinitionNames				this.beanDefinitionNames.add(beanName);				// 清除缓存				this.manualSingletonNames.remove(beanName);			}			// 清除缓存			this.frozenBeanDefinitionNames = null;		}		if (existingDefinition != null || containsSingleton(beanName)) {			resetBeanDefinition(beanName);		}	}复制代码

上述代码中首先验证了beanName和BeannDefinition不可为空,然后继续校验了MethodOverridesMethodOverrides在解析并组装beanDefinition时lookup-method和recpse-method的源码中有提到，继续判断beanDefinitionMap是否存在该bean，如果bean已经存在，通过allowBeanDefinitionOverriding属性判断是否可覆盖，反之则抛出异常；如果不存在则需要判断本次是否是第一次注册bean，如果是则初始化beanDefinitionMap后进行put操作，反之直接put beanDefinitionMap完成注册；

至此我们已经看完了整个XmlBeanFactory的xml解析和注册的源码部分，相信看本篇文章无法真正理解，还需要读者下载源码使用debug运行，再结合本篇文章的注释，相信会很容易理解，码字不易，转发请注明出处：或 https://juejin.im/editor/drafts/5c8c80b7f265da2dc23231da