内含大量源码

建议横屏观看

Spring IoC容器涉及到的类很多，启动过程比较复杂，大体分为两步：

1. 创建BeanFactory
2. 实例化Bean对象

鉴于公众号字数限制（5000）本文拆成上下两部分。

第一部分——创建BeanFactory

主要容器依赖关系：

以FileSystemXmlApplicationContext这个标准容器为例：

public FileSystemXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}

看到FileSystemXmlApplicationContext的构造器中有如下步骤： 1.初始化父容器AbstractApplicationContext

2.设置资源文件的位置：setConfigLocations

3.核心方法refresh(); 其实是在超类AbstractApplicationContext中定义的一个模版方法。

refresh()方法的定义是在AbstractApplicationContext的父接口ConfigurableApplicationContext中。再往上层追溯，可以发现ConfigurableApplicationContext的基类就是BeanFactory接口。

/**
* Load or refresh the persistent representation of the configuration,
* which might an XML file, properties file, or relational database schema.
* <p>As this is a startup method, it should destroy already created singletons
* if it fails, to avoid dangling resources. In other words, after invocation
* of that method, either all or no singletons at all should be instantiated.
* @throws BeansException if the bean factory could not be initialized
* @throws IllegalStateException if already initialized and multiple refresh
* attempts are not supported
*/
void refresh() throws BeansException, IllegalStateException;

AbstractApplicationContext类实现了ConfigurableApplicationContext接口。重写了refresh()方法。下面分析FileSystemXmlApplicationContext的超类AbstractApplicationContext中的refresh()方法：

@Override
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.
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();
}

AbstractApplicationContext中模版方法refresh()中定义了若干个步骤，其中最核心的是：

1. 创建BeanFactory：ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
2. 实例化Bean：finishBeanFactoryInitialization(beanFactory);

创建BeanFactory

AbstractApplicationContext

针对AbstractApplicationContext这个类做分析。断点进入obtainFreshBeanFactory()方法，该方法会返回ConfigurableListableBeanFactory对象。

也就是说这个obtainFreshBeanFactory()方法方法会返回一个BeanFactory对象。

obtainFreshBeanFactory()方法如下：

/**
* Tell the subclass to refresh the internal bean factory.
* @return the fresh BeanFactory instance
* @see #refreshBeanFactory()
* @see #getBeanFactory()
*/
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}

该方法分为两步：

1.刷新BeanFactory：refreshBeanFactory();

2.创建BeanFactory：getBeanFactory();

先进入refreshBeanFactory();方法，依然是模版方法，进入子类AbstractRefreshableApplicationContext的refreshBeanFactory方法中。

AbstractRefreshableApplicationContext

看下AbstractRefreshableApplicationContext中refreshBeanFactory()方法的实现：

/**
* This implementation performs an actual refresh of this context's underlying
* bean factory, shutting down the previous bean factory (if any) and
* initializing a fresh bean factory for the next phase of the context's lifecycle.
*/
@Override
protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
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);
}
}

这里refreshBeanFactory()方法的实现中，首先检查当前环境是否已经存在一个BeanFactory，如果已存在BeanFactory，则先销毁对应的bean，然后销毁BeanFactory。然后开始创建新的BeanFactory。

createBeanFactory()方法只是创建了一个空的BeanFactory。整个refreshBeanFactory()方法的核心在loadBeanDefinitions(beanFactory)中。

AbstractXmlApplicationContext

进入模版方法loadBeanDefinitions(beanFactory)的实现类AbstractXmlApplicationContext中

/**
* Loads the bean definitions via an XmlBeanDefinitionReader.
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
* @see #initBeanDefinitionReader
* @see #loadBeanDefinitions
*/
@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
XmlBeanDefinitionReader 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);
}

loadBeanDefinitions(DefaultListableBeanFactory beanFactory)方法中，通过上一步创建的空的BeanFactory来创建一个XmlBeanDefinitionReader对象。XmlBeanDefinitionReader是用来解析XML中定义的bean的。重点关注最后一个方法：loadBeanDefinitions(beanDefinitionReader)，这是一个重载的方法，这个方法的入参是刚刚生产的XmlBeanDefinitionReader对象。

重载的方法loadBeanDefinitions(XmlBeanDefinitionReader reader)如下：

/**
* Load the bean definitions with the given XmlBeanDefinitionReader.
* <p>The lifecycle of the bean factory is handled by the {@link #refreshBeanFactory}
* method; hence this method is just supposed to load and/or register bean definitions.
* @param reader the XmlBeanDefinitionReader to use
* @throws BeansException in case of bean registration errors
* @throws IOException if the required XML document isn't found
* @see #refreshBeanFactory
* @see #getConfigLocations
* @see #getResources
* @see #getResourcePatternResolver
*/
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);
}
}

可以看到，这个方法会调用XmlBeanDefinitionReader对象中的loadBeanDefinitions()方法中。

AbstractBeanDefinitionReader

从上图的集成关系可以发现，XmlBeanDefinitionReader是AbstractBeanDefinitionReader的子类。上述代码段reader.loadBeanDefinitions(configLocations);会调用其父类AbstractBeanDefinitionReader中的loadBeanDefinitions方法。最终会调用父类AbstractBeanDefinitionReader的重载方法：loadBeanDefinitions(String... locations)

@Override
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;
}

可以发现loadBeanDefinitions(String... locations)方法会遍历资源数组，最终会调用重载方法loadBeanDefinitions(String location, @Nullable Set<Resource> actualResources)：

/**
* Load bean definitions from the specified resource location.
* <p>The location can also be a location pattern, provided that the
* ResourceLoader of this bean definition reader is a ResourcePatternResolver.
* @param location the resource location, to be loaded with the ResourceLoader
* (or ResourcePatternResolver) of this bean definition reader
* @param actualResources a Set to be filled with the actual Resource objects
* that have been resolved during the loading process. May be {@code null}
* to indicate that the caller is not interested in those Resource objects.
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
* @see #getResourceLoader()
* @see #loadBeanDefinitions(org.springframework.core.io.Resource)
* @see #loadBeanDefinitions(org.springframework.core.io.Resource[])
*/
public int loadBeanDefinitions(String location, @Nullable 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 {
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
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;
}
}

这个方法会对文件路径进行解析，生成资源数组。然后loadBeanDefinitions(resources)对资源数据循环操作，加载Bean的定义。

loadBeanDefinitions(Resource... resources)方法如下：

@Override
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;
}

可以看到，loadBeanDefinitions(Resource... resources)方法在for循环中，调用loadBeanDefinitions(resource)方法，解析Bean。

loadBeanDefinitions(Resource resource)方法在最上层基类BeanDefinitionReader定义：

/**
* Load bean definitions from the specified resource.
* @param resource the resource descriptor
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
*/
int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException;

XmlBeanDefinitionReader

这里AbstractBeanDefinitionReader中对loadBeanDefinitions(Resource resource)的调用，会调用XmlBeanDefinitionReader子类中实现的方法：

/**
* 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 {
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<>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
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();
}
}
}

XmlBeanDefinitionReader的方法loadBeanDefinitions(EncodedResource encodedResource)的核心逻辑是doLoadBeanDefinitions(inputSource, encodedResource.getResource());这一行代码。载入Bean的定义。

进入doLoadBeanDefinitions(inputSource, encodedResource.getResource());方法

/**
* 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 {
Document doc = doLoadDocument(inputSource, resource);
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);
}
}

可以看出该方法主要逻辑是根据输入流加载 Document 文档对象，然后根据得到的文档对象，将定义的Bean注册到容器，调用 registerBeanDefinitions(doc, resource);进行注册，registerBeanDefinitions(doc, resource);定义如下：

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

这个方法的核心是调用documentReader.registerBeanDefinitions(doc, createReaderContext(resource));对Bean进行注册，registerBeanDefinitions是在BeanDefinitionDocumentReader中定义的：

public interface BeanDefinitionDocumentReader {/**
* Read bean definitions from the given DOM document and
* register them with the registry in the given reader context.
* @param doc the DOM document
* @param readerContext the current context of the reader
* (includes the target registry and the resource being parsed)
* @throws BeanDefinitionStoreException in case of parsing errors
*/
void registerBeanDefinitions(Document doc, XmlReaderContext readerContext)
throws BeanDefinitionStoreException;}

DefaultBeanDefinitionDocumentReader

这个接口的实现类是DefaultBeanDefinitionDocumentReader：

/**
* This implementation parses bean definitions according to the "spring-beans" XSD
* (or DTD, historically).
* <p>Opens a DOM Document; then initializes the default settings
* specified at the {@code <beans/>} level; then parses the contained bean definitions.
*/
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
doRegisterBeanDefinitions(root);
}

registerBeanDefinitions(Document doc, XmlReaderContext readerContext)是依靠doRegisterBeanDefinitions(root);来实现注册功能的。doRegisterBeanDefinitions(Element root)方法如下：

/**
* Register each bean definition within the given root {@code <beans/>} element.
*/
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;
this.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)) {
if (logger.isInfoEnabled()) {
logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec +
"] not matching: " + getReaderContext().getResource());
}
return;
}
}
}preProcessXml(root);
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);this.delegate = parent;
}

doRegisterBeanDefinitions(Element root)方法的核心功能是由parseBeanDefinitions(root, this.delegate);方法实现的。parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate)方法如下：

/**
* 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) {
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)) {
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}

parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate)方法主要逻辑是parseDefaultElement(ele, delegate);这一行代码。parseDefaultElement方法定义如下：

private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}

根据不同bean的配置不同，进入不同分支执行。选择processBeanDefinition(ele, delegate);方法进行分析：

/**
* Process the given bean element, parsing the bean definition
* and registering it with the registry.
*/
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder 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));
}
}

可以看到，BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());这一行是最终注册Bean的关键代码。

BeanDefinitionReaderUtils

/**
* Register the given bean definition with the given bean factory.
* @param definitionHolder the bean definition including name and aliases
* @param registry the bean factory to register with
* @throws BeanDefinitionStoreException if registration failed
*/
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
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);
}
}
}

registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());这一行是将Bean的名字和BeanDefinition对象进行注册的地方。

DefaultListableBeanFactory

@Override
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 existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
if (!isAllowBeanDefinitionOverriding()) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + existingDefinition + "] bound.");
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isWarnEnabled()) {
logger.warn("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.isInfoEnabled()) {
logger.info("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] 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<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
if (this.manualSingletonNames.contains(beanName)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
updatedSingletons.remove(beanName);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// Still in startup registration phase
this.beanDefinitionMap.put(beanName, beanDefinition);
this.beanDefinitionNames.add(beanName);
this.manualSingletonNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
}if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}

可以说该方法是Bean注册的最后一步，将beanName和 beanDefinition 放进一个 ConcurrentHashMap（256） 中。将所有的BeanName保存到beanDefinitionNames这个ArrayList<>(256)中。到此，创建Bean工厂完成，生成Bean定义并注册到了BeanFactory中。但是还没开始将Bean进行实例化。