舉例說明IoC容器的實現方式有哪些，Ioc容器beanDefinition－Spring 源碼系列（1）

2023-12-06 阅读 25 评论 0

摘要：Ioc容器beanDefinition－Spring?源碼系列（1）目錄： ? Ioc容器beanDefinition－Spring?源碼（1） Ioc容器依賴注入－Spring 源碼（2）舉例說明IoC容器的實現方式有哪些？Ioc容器BeanPostProcessor－Spr

Ioc容器beanDefinition－Spring?源碼系列（1）

目錄：

Ioc容器beanDefinition－Spring?源碼（1）

Ioc容器依賴注入－Spring 源碼（2）

舉例說明IoC容器的實現方式有哪些？Ioc容器BeanPostProcessor－Spring 源碼（3）

事件機制－Spring 源碼（4）

AOP執行增強－Spring 源碼系列（5）

beanpropertybindingresult？1，理解控制反轉??

以前一直說著這個詞，然后把它等于上ioc這個詞，再等于上代碼里一個bean里依賴了其他bean，不用new，用注解，用xml去描述，就可以了。能用就行了，實際理論的不管也不影響編碼，其實能用了內心也是理解是怎么回事的，知識理論上說不好而已。

我覺得只要理解一個事情就好了，ioc所謂的控制翻轉，它控制翻轉的是什么？

依賴對象的獲得被反轉

把一個bean中對其他bean的依賴這個事提取出來，統一由一個容器管理，解耦了bean管理和業務的代碼（工廠方法模式不就干這事嘛）

最后，Spring提供了一個IoC容器來管理對象的生命周期、依賴關系，這也是spring的最核心的基礎組件。

其實控制反轉也是一種設計模式，的確，從項目層面抽取了管理bean依賴關系，徹底解耦bean注入和業務代碼，也是一種軟件開發中的思想。

2，IoC容器

它要完成什么事？

通過解析bean依賴關系的描述，容器需要創建出項目中所有需要管理的bean，然后注入。

那么拆成打的兩步：1，把依賴關系描述解析成bean；2，把bean注入

但是，既然是bean之間有依賴關系，當生產一個bean時，它依賴的bean也需要已經產生，所以在一個軟件中，觸發開始初始化容器的時候是把項目中用到的bean看成樹結構的樣子，然后一次遞歸的生產bean，注入。有點像目錄結構遍歷。

比如：A依賴B B依賴C，那么A生產時會觸發B生產，然后觸發C生產。

所以，我們閱讀IoC源碼時也會看到這樣的實現。

3，IoC容器的實現

BeanFactory和ApplicationContext

BeanFactory是容器基礎設計，ApplicationContext增加了針對企業軟件一些擴展功能，應該說后者是前者的高級形態。

public interface BeanFactory {/*** 用來獲取FactoryBean本身的轉義符*/String FACTORY_BEAN_PREFIX = "&";/*** 獲取容器維護的bean是用名稱來指定的*/Object getBean(String name) throws BeansException;<T> T getBean(String name, Class<T> requiredType) throws BeansException;<T> T getBean(Class<T> requiredType) throws BeansException;Object getBean(String name, Object... args) throws BeansException;<T> T getBean(Class<T> requiredType, Object... args) throws BeansException;/*** 查看容器中是否包含指定name的bean*/boolean containsBean(String name);/*** 判斷指定name的bean是否為單例*/boolean isSingleton(String name) throws NoSuchBeanDefinitionException;/*** 判斷指定name的bean是否為多例*/boolean isPrototype(String name) throws NoSuchBeanDefinitionException;boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException;Class<?> getType(String name) throws NoSuchBeanDefinitionException;/*** 獲得bean的所有別名*/String[] getAliases(String name);}

BeanFactory設計定義了ioc的規范。

DefaultListableBeanFactory <—?XmlBeanFactory

DefaultListableBeanFactory有容器的完整實現，而XmlBeanFactory是對它的一種擴展，擴展什么看名字就知道了，支持xml數據源的解析。我們看下XmlBeanFactory的代碼：

public class XmlBeanFactory extends DefaultListableBeanFactory {/*** 換了一個reader*/private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);public XmlBeanFactory(Resource resource) throws BeansException {this(resource, null);}public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {super(parentBeanFactory);this.reader.loadBeanDefinitions(resource);}}

XmlBeanFactory在初始化時調用loadBeanDefinitions方法，使用XmlBeanDefinitionReader去解析元數據，這也是最初的一步。

FileSystemXmlApplicationContext源碼：

public class FileSystemXmlApplicationContext extends AbstractXmlApplicationContext {public FileSystemXmlApplicationContext() {}public FileSystemXmlApplicationContext(ApplicationContext parent) {super(parent);}public FileSystemXmlApplicationContext(String configLocation) throws BeansException {this(new String[] {configLocation}, true, null);}public FileSystemXmlApplicationContext(String... configLocations) throws BeansException {this(configLocations, true, null);}public FileSystemXmlApplicationContext(String[] configLocations, ApplicationContext parent) throws BeansException {this(configLocations, true, parent);}public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh) throws BeansException {this(configLocations, refresh, null);}/*** setConfigLocations 將路徑字符串解析到自己存資源配置的configLocations里* 然后調用refresh()，這也是容器初始化的入口* */public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)throws BeansException {super(parent);setConfigLocations(configLocations);if (refresh) {refresh();}}/*** 這是這個FileSystemXml自己的實現部分，getResourceByPath必然是哪一個父類模版方法需要調用的方法* 而這個方法自己實現提供一個FileSystemResource出來。* Resource這個就是將元數據轉化成容器可以統一可以解析的資源，根據不同的元數據類型，必然需要不同的算法去讀取這些數據。*/@Overrideprotected Resource getResourceByPath(String path) {if (path != null && path.startsWith("/")) {path = path.substring(1);}return new FileSystemResource(path);}}

Spring ioc、?

調用AbstractApplicationContext的refresh方法：

標準的模版方法，這里注意繼承鏈路，嵌套的模版方法調用下來。

    public void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {// Prepare this context for refreshing.
            prepareRefresh();// Tell the subclass to refresh the internal bean factory.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.// 擴展點1
                invokeBeanFactoryPostProcessors(beanFactory);// Register bean processors that intercept bean creation.// 擴展點2
                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) {// Destroy already created singletons to avoid dangling resources.
                destroyBeans();// Reset 'active' flag.
                cancelRefresh(ex);// Propagate exception to caller.throw ex;}}}

調用AbstractApplicationContext 的obtainFreshBeanFactory方法：

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {// 這要調用子類的實現=>AbstractRefreshableApplicationContext
        refreshBeanFactory();ConfigurableListableBeanFactory beanFactory = getBeanFactory();if (logger.isDebugEnabled()) {logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);}return beanFactory;}

AbstractRefreshableApplicationContext的refreshBeanFactory

BeanUtils，?

protected final void refreshBeanFactory() throws BeansException {if (hasBeanFactory()) {destroyBeans();closeBeanFactory();}try {DefaultListableBeanFactory beanFactory = createBeanFactory();beanFactory.setSerializationId(getId());customizeBeanFactory(beanFactory);// 子類實現
            loadBeanDefinitions(beanFactory);synchronized (this.beanFactoryMonitor) {this.beanFactory = beanFactory;}}catch (IOException ex) {throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);}}

AbstractXmlApplicationContext的loadBeanDefinitions

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {// Create a new XmlBeanDefinitionReader for the given BeanFactory.// 指定ReaderXmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);// Configure the bean definition reader with this context's// resource loading environment.beanDefinitionReader.setEnvironment(this.getEnvironment());beanDefinitionReader.setResourceLoader(this);beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));// Allow a subclass to provide custom initialization of the reader,// then proceed with actually loading the bean definitions.
        initBeanDefinitionReader(beanDefinitionReader);//
        loadBeanDefinitions(beanDefinitionReader);}protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {Resource[] configResources = getConfigResources();if (configResources != null) {reader.loadBeanDefinitions(configResources);}String[] configLocations = getConfigLocations();if (configLocations != null) {reader.loadBeanDefinitions(configLocations);}}

XmlBeanDefinitionReader繼承的基類AbstractBeanDefinitionReader的實現：

public 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;}public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {return loadBeanDefinitions(location, null);}public 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;}/**最終調用到的實現，這里需要產生Resource，既然用FileSystemXmlApplicationContext* 那在讀取文件產生Resource的過程有它自定義的部分，也就是我們在FileSystemXmlApplicationContext中看到的getResourceByPath會被使用。*/public int loadBeanDefinitions(String location, Set<Resource> actualResources) throws BeanDefinitionStoreException {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 {// 要產生Resource了Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);// 這里是解析Resource的入口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;}}

回到AbstractApplicationContext調用getResources方法，resourcePatternResolver用默認的PathMatchingResourcePatternResolver

public Resource[] getResources(String locationPattern) throws IOException {return this.resourcePatternResolver.getResources(locationPattern);}
public AbstractApplicationContext() {this.resourcePatternResolver = getResourcePatternResolver();}//默認PathMatchingResourcePatternResolver
protected ResourcePatternResolver getResourcePatternResolver() {return new PathMatchingResourcePatternResolver(this);}

PathMatchingResourcePatternResolver的getResources實現

public Resource[] getResources(String locationPattern) throws IOException {Assert.notNull(locationPattern, "Location pattern must not be null");// 一種是classpath開頭 一種沒有if (locationPattern.startsWith(CLASSPATH_ALL_URL_PREFIX)) {// a class path resource (multiple resources for same name possible)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 {// Only look for a pattern after a prefix here// (to not get fooled by a pattern symbol in a strange prefix).int prefixEnd = locationPattern.indexOf(":") + 1;if (getPathMatcher().isPattern(locationPattern.substring(prefixEnd))) {// a file patternreturn findPathMatchingResources(locationPattern);}else {// a single resource with the given name// 使用ResourceLoader來產生Resourcereturn new Resource[] {getResourceLoader().getResource(locationPattern)};}}}// 默認使用DefaultResourceLoader來解析路徑public PathMatchingResourcePatternResolver(ClassLoader classLoader) {this.resourceLoader = new DefaultResourceLoader(classLoader);}public ResourceLoader getResourceLoader() {return this.resourceLoader;}

java的io流、DefaultResourceLoader的getResource，而此時返回的Resource是FileSystemResource類型

public Resource getResource(String location) {Assert.notNull(location, "Location must not be null");if (location.startsWith("/")) {// 最終調用子類的getResourceByPath，而這個方法正是FileSystemXmlApplicationContext實現的return getResourceByPath(location);}else if (location.startsWith(CLASSPATH_URL_PREFIX)) {return new ClassPathResource(location.substring(CLASSPATH_URL_PREFIX.length()), getClassLoader());}else {try {// Try to parse the location as a URL...URL url = new URL(location);return new UrlResource(url);}catch (MalformedURLException ex) {// No URL -> resolve as resource path.return getResourceByPath(location);}}
}

可見FileSystemXmlApplicationContext最終體現在產生的Resource不同實現。

Resource相當于定位到資源的抽象，下一步就是不同Resource解析資源。

回到AbstractBeanDefinitionReader的loadBeanDefinitions。定位后下一步就是解析Resource的入口：

int loadCount = loadBeanDefinitions(resource);

子類XmlBeanDefinitionReader實現：

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());}Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();if (currentResources == null) {currentResources = new HashSet<EncodedResource>(4);this.resourcesCurrentlyBeingLoaded.set(currentResources);}if (!currentResources.add(encodedResource)) {throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!");}try {// 終于到了java讀取文件熟悉的InputStream了，Recoure－>InputStreamInputStream inputStream = encodedResource.getResource().getInputStream();try {InputSource inputSource = new InputSource(inputStream);if (encodedResource.getEncoding() != null) {inputSource.setEncoding(encodedResource.getEncoding());}// 繼續解析：InputStream -> Documentreturn 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();}}}

調用到DefaultDocumentLoader實現解析xml

protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)throws BeanDefinitionStoreException {try {// 繼續解析：InputStream -> DocumentDocument doc = doLoadDocument(inputSource, resource);// 轉化：Document->BeanDefinition// 顯然，從一個Document變成一個個bean的描述（BeanDefinition），就涉及到我們在使用spring時經常用到的bean定義時的各種配置規則，如果查看源碼，也許會更好的理解。return registerBeanDefinitions(doc, resource);}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);}}// 具體documentLoader來實現，DefaultDocumentLoader實現解析xmlprotected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,getValidationModeForResource(resource), isNamespaceAware());}

DefaultDocumentLoader使用JAXP方式解析：

public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);if (logger.isDebugEnabled()) {logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");}DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);return builder.parse(inputSource);}protected DocumentBuilder createDocumentBuilder(DocumentBuilderFactory factory, EntityResolver entityResolver, ErrorHandler errorHandler)throws ParserConfigurationException {DocumentBuilder docBuilder = factory.newDocumentBuilder();if (entityResolver != null) {docBuilder.setEntityResolver(entityResolver);}if (errorHandler != null) {docBuilder.setErrorHandler(errorHandler);}return docBuilder;}

registerBeanDefinitions方法：

public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();int countBefore = getRegistry().getBeanDefinitionCount();//BeanDefinitionDocumentReader具體實現
        documentReader.registerBeanDefinitions(doc, createReaderContext(resource));return getRegistry().getBeanDefinitionCount() - countBefore;}

BeanDefinitionDocumentReader具體實現：

public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {this.readerContext = readerContext;logger.debug("Loading bean definitions");Element root = doc.getDocumentElement();doRegisterBeanDefinitions(root);}protected void doRegisterBeanDefinitions(Element root) {// Any nested <beans> elements will cause recursion in this method. In// order to propagate and preserve <beans> 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;// 指定好BeanDefinitionParserDelegatethis.delegate = createDelegate(getReaderContext(), root, parent);if (this.delegate.isDefaultNamespace(root)) {String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);if (StringUtils.hasText(profileSpec)) {String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {return;}}}//可擴展入口
        preProcessXml(root);parseBeanDefinitions(root, this.delegate);postProcessXml(root);this.delegate = parent;}protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {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)) {// 一次解析每個節點
                        parseDefaultElement(ele, delegate);}else {delegate.parseCustomElement(ele);}}}}else {delegate.parseCustomElement(root);}}//標簽解析private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {//import
            importBeanDefinitionResource(ele);}else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {//alias
            processAliasRegistration(ele);}else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {//bean
            processBeanDefinition(ele, delegate);}else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {// beans recurse
            doRegisterBeanDefinitions(ele);}}

如果是beans的標簽則進行了遞歸，查看解析bean標簽的代碼：

protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {// 終于是解析入口了,Element－>BeanDefinitionHolderBeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);if (bdHolder != null) {bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);try {// Register the final decorated instance.
                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));}}public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {return parseBeanDefinitionElement(ele, null);}

這里的BeanDefinitionHolder包裝了BeanDefinition以及bean和alias：

private final BeanDefinition beanDefinition;private final String beanName;private final String[] aliases;

BeanDefinitionReaderUtils.registerBeanDefinition：

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {// bean idString id = ele.getAttribute(ID_ATTRIBUTE);// bean nameString nameAttr = ele.getAttribute(NAME_ATTRIBUTE);List<String> aliases = new ArrayList<String>();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.isDebugEnabled()) {logger.debug("No XML 'id' specified - using '" + beanName +"' as bean name and " + aliases + " as aliases");}}if (containingBean == null) {checkNameUniqueness(beanName, aliases, ele);}
// beanDefinition產生 此時已經解析了bean中的其他字段AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);if (beanDefinition != null) {if (!StringUtils.hasText(beanName)) {try {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.isDebugEnabled()) {logger.debug("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;}

拿到holder后進行注冊：

    public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)throws BeanDefinitionStoreException {// Register bean definition under primary name.String beanName = definitionHolder.getBeanName();// 把解析出來到BeanDefinition進行注冊
        registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());// Register aliases for bean name, if any.String[] aliases = definitionHolder.getAliases();if (aliases != null) {for (String alias : aliases) {registry.registerAlias(beanName, alias);}}}

最終DefaultListableBeanFactory中的代碼：

public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)throws BeanDefinitionStoreException {Assert.hasText(beanName, "Bean name must not be empty");Assert.notNull(beanDefinition, "BeanDefinition must not be null");if (beanDefinition instanceof AbstractBeanDefinition) {try {((AbstractBeanDefinition) beanDefinition).validate();}catch (BeanDefinitionValidationException ex) {throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,"Validation of bean definition failed", ex);}}BeanDefinition oldBeanDefinition;oldBeanDefinition = this.beanDefinitionMap.get(beanName);if (oldBeanDefinition != null) {if (!isAllowBeanDefinitionOverriding()) {throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +"': There is already [" + oldBeanDefinition + "] bound.");}else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTUREif (this.logger.isWarnEnabled()) {this.logger.warn("Overriding user-defined bean definition for bean '" + beanName +"' with a framework-generated bean definition: replacing [" +oldBeanDefinition + "] with [" + beanDefinition + "]");}}else if (!beanDefinition.equals(oldBeanDefinition)) {if (this.logger.isInfoEnabled()) {this.logger.info("Overriding bean definition for bean '" + beanName +"' with a different definition: replacing [" + oldBeanDefinition +"] with [" + beanDefinition + "]");}}else {if (this.logger.isDebugEnabled()) {this.logger.debug("Overriding bean definition for bean '" + beanName +"' with an equivalent definition: replacing [" + oldBeanDefinition +"] with [" + beanDefinition + "]");}}this.beanDefinitionMap.put(beanName, beanDefinition);}else {if (hasBeanCreationStarted()) {// Cannot modify startup-time collection elements anymore (for stable iteration)synchronized (this.beanDefinitionMap) {this.beanDefinitionMap.put(beanName, beanDefinition);List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);updatedDefinitions.addAll(this.beanDefinitionNames);updatedDefinitions.add(beanName);this.beanDefinitionNames = updatedDefinitions;if (this.manualSingletonNames.contains(beanName)) {Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);updatedSingletons.remove(beanName);this.manualSingletonNames = updatedSingletons;}}}else {// Still in startup registration phasethis.beanDefinitionMap.put(beanName, beanDefinition);this.beanDefinitionNames.add(beanName);this.manualSingletonNames.remove(beanName);}this.frozenBeanDefinitionNames = null;}if (oldBeanDefinition != null || containsSingleton(beanName)) {resetBeanDefinition(beanName);}}