Spring4源码分析(ClassPathXmlApplicationContext)

Spring4源码分析(ClassPathXmlApplicationContext)
类图
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适当删减了一部分
后边部分构成了BeanFactory的结构体系
BeanFactory提供了获取Bean对象的方法
HierarchicalBeanFactory提供了获取父BeanFactory的方法
ConfigurableBeanFactory提供了设置父BeanFactory的方法
AutowireCapableBeanFactory提供了创建Bean的方法
ListableBeanFactory提供了查找Bean的方法
ConfigurableListableBeanFactory实现了ConfigurableBeanFactory, AutowireCapableBeanFactory, ListableBeanFactory,同事提供了查找BeanDefinition的方法

中间部门实现了左边对应的接口
AbstractBeanFactory
AbstractAutowireCapableBeanFactory
DefaultListableBeanFactory
构成了整个的BeanFactory工厂
提供了BeanFactory的默认实现

左边部分提供了ApplicationContext接口
AbstractApplicationContext
AbstractRefreshableApplicationContext
AbstractRefreshableConfigApplicationContext
AbstractXmlApplicationContext
ClassPathXmlApplicationContext
对BeanFactory做了二次封装

1. 初始化

时序图

1.1 ClassPathXmlApplicationContext:设置了Xml配置文件的位置

public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext {public ClassPathXmlApplicationContext(String configLocation) throws BeansException {this(new String[]{configLocation}, true, null);}public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)throws BeansException {//调用父类的构造方法,设置父类的ApplicationContext,默认为空super(parent);//设置配置文件setConfigLocations(configLocations);if (refresh) {//调用父类的方法,由AbstractApplicationContext实现refresh();}}}

1.2 AbstractRefreshableConfigApplicationContext提供了设置配置文件的功能

public abstract class AbstractRefreshableConfigApplicationContext extends AbstractRefreshableApplicationContextimplements BeanNameAware, InitializingBean {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++) {      //设置配置文件的地址this.configLocations[i] = resolvePath(locations[i]).trim();}} else {this.configLocations = null;}}}

1.3 AbstractApplicationContext提供了刷新容器抽象的方法

public abstract class AbstractApplicationContext extends DefaultResourceLoaderimplements ConfigurableApplicationContext, DisposableBean {@Overridepublic void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {// 刷新前执行的方法 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();} 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();}}}protected void prepareRefresh() {this.startupDate = System.currentTimeMillis();this.closed.set(false);this.active.set(true);if (logger.isInfoEnabled()) {logger.info("Refreshing " + this);}// Initialize any placeholder property sources in the context environment   initPropertySources(); ConfigurablePropertyResolver#setRequiredProperties   getEnvironment().validateRequiredProperties();           this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>(); }protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {refreshBeanFactory();ConfigurableListableBeanFactory beanFactory = getBeanFactory();if (logger.isDebugEnabled()) {logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);}return beanFactory;}}

1.4 AbstractRefreshableApplicationContext实现了抽象方法refreshBeanFactory,并创建了DefaultListableBeanFactory对象

public abstract class AbstractRefreshableApplicationContext extends AbstractApplicationContext {@Overrideprotected final void refreshBeanFactory() throws BeansException {if (hasBeanFactory()) {destroyBeans();closeBeanFactory();}try {//创建DefaultListableBeanFactoryDefaultListableBeanFactory beanFactory = createBeanFactory();beanFactory.setSerializationId(getId());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);}}protected DefaultListableBeanFactory createBeanFactory() {return new DefaultListableBeanFactory(getInternalParentBeanFactory());}}

1.5 AbstractXmlApplicationContext完成了对Xml配置文件的解析,创建了XmlBeanDefinitionReader对象

public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext {protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {// 创建XmlBeanDefinitionReaderXmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);beanDefinitionReader.setEnvironment(this.getEnvironment());beanDefinitionReader.setResourceLoader(this);beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));initBeanDefinitionReader(beanDefinitionReader);//加载BeanDefinitionloadBeanDefinitions(beanDefinitionReader);}protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {Resource[] configResources = getConfigResources();if (configResources != null) {reader.loadBeanDefinitions(configResources);}String[] configLocations = getConfigLocations();if (configLocations != null) {//通过XmlBeanDefinitionReader加载BeanDefinitionreader.loadBeanDefinitions(configLocations);}}}

1.6 AbstractBeanDefinitionReader抽象了配置文件解析的功能

public abstract class AbstractBeanDefinitionReader implements EnvironmentCapable, BeanDefinitionReader {@Overridepublic int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {Assert.notNull(resources, "Resource array must not be null");int counter = 0;for (Resource resource : resources) {//加载BeanDefinitioncounter += loadBeanDefinitions(resource);}return counter;}@Overridepublic int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {return loadBeanDefinitions(location, null);}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 {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 {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;}}@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;}}

1.7 XmlBeanDefinitionReader完成对具体的xml格式配置文件的解析,具体的解析由BeanDefinitionDocumentReader完成

public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {@Overridepublic int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {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());}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 {InputStream inputStream = encodedResource.getResource().getInputStream();try {InputSource inputSource = new InputSource(inputStream);if (encodedResource.getEncoding() != null) {inputSource.setEncoding(encodedResource.getEncoding());}//加载BeanDefinitionreturn 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 {//加载XML文档Document doc = doLoadDocument(inputSource, resource);//注册BeanDefinitionreturn 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);}}protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,getValidationModeForResource(resource), isNamespaceAware());}public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {//创建BeanDefinition文档阅读器BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();int countBefore = getRegistry().getBeanDefinitionCount();//注册BeanDefinitiondocumentReader.registerBeanDefinitions(doc, createReaderContext(resource));return getRegistry().getBeanDefinitionCount() - countBefore;}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());}}

1.8 DefaultBeanDefinitionDocumentReader通过BeanDefinitionParserDelegate完成对具体XML的解析

public class DefaultBeanDefinitionDocumentReader implements BeanDefinitionDocumentReader {@Overridepublic void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {this.readerContext = readerContext;logger.debug("Loading bean definitions");Element root = doc.getDocumentElement();//注册BeanDefinitiondoRegisterBeanDefinitions(root);}protected final XmlReaderContext getReaderContext() {return this.readerContext;}protected Object extractSource(Element ele) {return getReaderContext().extractSource(ele);}protected void doRegisterBeanDefinitions(Element root) {BeanDefinitionParserDelegate parent = this.delegate;//创建BeanDefinition解析器this.delegate = createDelegate(getReaderContext(), root, parent);//如果是默认命名空间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);//解析BeanDefinitionparseBeanDefinitions(root, this.delegate);postProcessXml(root);this.delegate = parent;}protected BeanDefinitionParserDelegate createDelegate(XmlReaderContext readerContext, Element root, BeanDefinitionParserDelegate parentDelegate) {BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext);delegate.initDefaults(root, parentDelegate);return delegate;}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)) {//默认命名空间parseDefaultElement(ele, delegate);}else {delegate.parseCustomElement(ele);}}}}else {delegate.parseCustomElement(root);}}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)) {//解析BeanDefinitionprocessBeanDefinition(ele, delegate);}else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {doRegisterBeanDefinitions(ele);}}protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {//解析BeanDefinition元素,返回BeanDefinitionHolder对象BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);if (bdHolder != null) {bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);try {      //注册BeanDefinitionBeanDefinitionReaderUtils.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));}}}

1.9 BeanDefinitionParserDelegate完成对具体的XML的解析,创建了BeanDefinition对象,并注册到了beanFactory工厂

public class BeanDefinitionParserDelegate {public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {//解析BeanDefinition元素return parseBeanDefinitionElement(ele, null);}public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {//获取IDString id = ele.getAttribute(ID_ATTRIBUTE);//获取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);}//解析BeanDefinition元素,返回BeanDefinitionAbstractBeanDefinition 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);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);//返回BeanDefinitionHolderreturn new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);}return null;}public AbstractBeanDefinition parseBeanDefinitionElement(Element ele, String beanName, BeanDefinition containingBean) {this.parseState.push(new BeanEntry(beanName));String className = null;if (ele.hasAttribute(CLASS_ATTRIBUTE)) {//获取ClassNameclassName = ele.getAttribute(CLASS_ATTRIBUTE).trim();}try {String parent = null;if (ele.hasAttribute(PARENT_ATTRIBUTE)) {parent = ele.getAttribute(PARENT_ATTRIBUTE);}//创建BeanDefinitionAbstractBeanDefinition bd = createBeanDefinition(className, parent);parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);//获取descriptionbd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));parseMetaElements(ele, bd);parseLookupOverrideSubElements(ele, bd.getMethodOverrides());parseReplacedMethodSubElements(ele, bd.getMethodOverrides());parseConstructorArgElements(ele, bd);parsePropertyElements(ele, bd);parseQualifierElements(ele, bd);//设置资源文件bd.setResource(this.readerContext.getResource());bd.setSource(extractSource(ele));//返回BeanDefinitionreturn 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;}protected AbstractBeanDefinition createBeanDefinition(String className, String parentName)throws ClassNotFoundException {return BeanDefinitionReaderUtils.createBeanDefinition(parentName, className, this.readerContext.getBeanClassLoader());}}

2 运行

2.1 AbstractApplicationContext提供了getBean方法

public abstract class AbstractApplicationContext extends DefaultResourceLoaderimplements ConfigurableApplicationContext, DisposableBean {@Overridepublic Object getBean(String name) throws BeansException {assertBeanFactoryActive();return getBeanFactory().getBean(name);}}

2.2 AbstractRefreshableApplicationContext提供了getBeanFactory方法

public abstract class AbstractRefreshableApplicationContext extends AbstractApplicationContext {@Overridepublic final ConfigurableListableBeanFactory getBeanFactory() {synchronized (this.beanFactoryMonitor) {if (this.beanFactory == null) {throw new IllegalStateException("BeanFactory not initialized or already closed - " +"call 'refresh' before accessing beans via the ApplicationContext");}return this.beanFactory;}}}

2.3 AbstractBeanFactory提供了getBean方法获取Bean的实例

public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {@Overridepublic Object getBean(String name) throws BeansException {//获取Beanreturn doGetBean(name, null, null, false);}public <T> T getBean(String name, Class<T> requiredType, Object... args) throws BeansException {return doGetBean(name, requiredType, args, false);}@SuppressWarnings("unchecked")protected <T> T doGetBean(final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)throws BeansException {final String beanName = transformedBeanName(name);Object bean;Object sharedInstance = getSingleton(beanName);if (sharedInstance != null && args == null) {if (logger.isDebugEnabled()) {if (isSingletonCurrentlyInCreation(beanName)) {logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +"' that is not fully initialized yet - a consequence of a circular reference");} else {logger.debug("Returning cached instance of singleton bean '" + beanName + "'");}}bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);} else {if (isPrototypeCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName);}BeanFactory parentBeanFactory = getParentBeanFactory();if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {String nameToLookup = originalBeanName(name);if (args != null) {return (T) parentBeanFactory.getBean(nameToLookup, args);} else {return parentBeanFactory.getBean(nameToLookup, requiredType);}}if (!typeCheckOnly) {markBeanAsCreated(beanName);}try {//获取BeanDefinitionfinal RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);checkMergedBeanDefinition(mbd, beanName, args);String[] dependsOn = mbd.getDependsOn();if (dependsOn != null) {for (String dep : dependsOn) {if (isDependent(beanName, dep)) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");}registerDependentBean(dep, beanName);getBean(dep);}}if (mbd.isSingleton()) {sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {@Overridepublic Object getObject() throws BeansException {try {//创建Beanreturn createBean(beanName, mbd, args);} catch (BeansException ex) {destroySingleton(beanName);throw ex;}}});bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);} else if (mbd.isPrototype()) {Object prototypeInstance = null;try {beforePrototypeCreation(beanName);prototypeInstance = createBean(beanName, mbd, args);} finally {afterPrototypeCreation(beanName);}bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);} else {String scopeName = mbd.getScope();final Scope scope = this.scopes.get(scopeName);if (scope == null) {throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");}try {Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {@Overridepublic Object getObject() throws BeansException {beforePrototypeCreation(beanName);try {return createBean(beanName, mbd, args);} finally {afterPrototypeCreation(beanName);}}});bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);} catch (IllegalStateException ex) {throw new BeanCreationException(beanName,"Scope '" + scopeName + "' is not active for the current thread; consider " +"defining a scoped proxy for this bean if you intend to refer to it from a singleton",ex);}}} catch (BeansException ex) {cleanupAfterBeanCreationFailure(beanName);throw ex;}}if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {try {return getTypeConverter().convertIfNecessary(bean, requiredType);} catch (TypeMismatchException ex) {if (logger.isDebugEnabled()) {logger.debug("Failed to convert bean '" + name + "' to required type '" +ClassUtils.getQualifiedName(requiredType) + "'", ex);}throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());}}return (T) bean;}protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {// Quick check on the concurrent map first, with minimal locking.RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);if (mbd != null) {return mbd;}//获取BeanDefinitionreturn getMergedBeanDefinition(beanName, getBeanDefinition(beanName));}protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd)throws BeanDefinitionStoreException {//获取BeanDefinitionreturn getMergedBeanDefinition(beanName, bd, null);}protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd, BeanDefinition containingBd)throws BeanDefinitionStoreException {synchronized (this.mergedBeanDefinitions) {RootBeanDefinition mbd = null;if (containingBd == null) {mbd = this.mergedBeanDefinitions.get(beanName);}if (mbd == null) {if (bd.getParentName() == null) {// Use copy of given root bean definition.if (bd instanceof RootBeanDefinition) {mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();}else {//重新创建RootBeanDefinitionmbd = new RootBeanDefinition(bd);}}else {// Child bean definition: needs to be merged with parent.BeanDefinition pbd;try {String parentBeanName = transformedBeanName(bd.getParentName());if (!beanName.equals(parentBeanName)) {pbd = getMergedBeanDefinition(parentBeanName);}else {BeanFactory parent = getParentBeanFactory();if (parent instanceof ConfigurableBeanFactory) {pbd = ((ConfigurableBeanFactory) parent).getMergedBeanDefinition(parentBeanName);}else {throw new NoSuchBeanDefinitionException(parentBeanName,"Parent name '" + parentBeanName + "' is equal to bean name '" + beanName +"': cannot be resolved without an AbstractBeanFactory parent");}}}catch (NoSuchBeanDefinitionException ex) {throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,"Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);}mbd = new RootBeanDefinition(pbd);mbd.overrideFrom(bd);}if (!StringUtils.hasLength(mbd.getScope())) {mbd.setScope(RootBeanDefinition.SCOPE_SINGLETON);}if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {mbd.setScope(containingBd.getScope());}if (containingBd == null && isCacheBeanMetadata()) {this.mergedBeanDefinitions.put(beanName, mbd);}}return mbd;}}}

2.4 AbstractAutowireCapableBeanFactory提供了创建实例的方法,对应的实例又InstantiationStrategy根据策略创建

public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactoryimplements AutowireCapableBeanFactory {protected InstantiationStrategy getInstantiationStrategy() {return this.instantiationStrategy;}@Overrideprotected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {if (logger.isDebugEnabled()) {logger.debug("Creating instance of bean '" + beanName + "'");}RootBeanDefinition mbdToUse = mbd;Class<?> resolvedClass = resolveBeanClass(mbd, beanName);if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {mbdToUse = new RootBeanDefinition(mbd);mbdToUse.setBeanClass(resolvedClass);}try {mbdToUse.prepareMethodOverrides();}catch (BeanDefinitionValidationException ex) {throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),beanName, "Validation of method overrides failed", ex);}try {Object bean = resolveBeforeInstantiation(beanName, mbdToUse);if (bean != null) {return bean;}}catch (Throwable ex) {throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,"BeanPostProcessor before instantiation of bean failed", ex);}//创建Bean实例Object beanInstance = doCreateBean(beanName, mbdToUse, args);if (logger.isDebugEnabled()) {logger.debug("Finished creating instance of bean '" + beanName + "'");}return beanInstance;}protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)throws BeanCreationException {BeanWrapper instanceWrapper = null;if (mbd.isSingleton()) {instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);}if (instanceWrapper == null) {//创建Bean实例instanceWrapper = createBeanInstance(beanName, mbd, args);}final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);mbd.resolvedTargetType = beanType;synchronized (mbd.postProcessingLock) {if (!mbd.postProcessed) {try {applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);}catch (Throwable ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"Post-processing of merged bean definition failed", ex);}mbd.postProcessed = true;}}boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&isSingletonCurrentlyInCreation(beanName));if (earlySingletonExposure) {if (logger.isDebugEnabled()) {logger.debug("Eagerly caching bean '" + beanName +"' to allow for resolving potential circular references");}addSingletonFactory(beanName, new ObjectFactory<Object>() {@Overridepublic Object getObject() throws BeansException {return getEarlyBeanReference(beanName, mbd, bean);}});}Object exposedObject = bean;try {populateBean(beanName, mbd, instanceWrapper);if (exposedObject != null) {exposedObject = initializeBean(beanName, exposedObject, mbd);}}catch (Throwable ex) {if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {throw (BeanCreationException) ex;}else {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);}}if (earlySingletonExposure) {Object earlySingletonReference = getSingleton(beanName, false);if (earlySingletonReference != null) {if (exposedObject == bean) {exposedObject = earlySingletonReference;}else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {String[] dependentBeans = getDependentBeans(beanName);Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);for (String dependentBean : dependentBeans) {if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {actualDependentBeans.add(dependentBean);}}if (!actualDependentBeans.isEmpty()) {throw new BeanCurrentlyInCreationException(beanName,"Bean with name '" + beanName + "' has been injected into other beans [" +StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +"] in its raw version as part of a circular reference, but has eventually been " +"wrapped. This means that said other beans do not use the final version of the " +"bean. This is often the result of over-eager type matching - consider using " +"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");}}}}try {registerDisposableBeanIfNecessary(beanName, bean, mbd);}catch (BeanDefinitionValidationException ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);}return exposedObject;}protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {Class<?> beanClass = resolveBeanClass(mbd, beanName);if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());}if (mbd.getFactoryMethodName() != null)  {return instantiateUsingFactoryMethod(beanName, mbd, args);}// Shortcut when re-creating the same bean...boolean resolved = false;boolean autowireNecessary = false;if (args == null) {synchronized (mbd.constructorArgumentLock) {if (mbd.resolvedConstructorOrFactoryMethod != null) {resolved = true;autowireNecessary = mbd.constructorArgumentsResolved;}}}if (resolved) {if (autowireNecessary) {return autowireConstructor(beanName, mbd, null, null);}else {return instantiateBean(beanName, mbd);}}Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);if (ctors != null ||mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {return autowireConstructor(beanName, mbd, ctors, args);}// 创建对象return instantiateBean(beanName, mbd);}protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {try {Object beanInstance;final BeanFactory parent = this;if (System.getSecurityManager() != null) {beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {@Overridepublic Object run() {return getInstantiationStrategy().instantiate(mbd, beanName, parent);}}, getAccessControlContext());}else {// 初始化对象beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);}//Bean包装器BeanWrapper bw = new BeanWrapperImpl(beanInstance);initBeanWrapper(bw);return bw;}catch (Throwable ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);}}}

2.5 SimpleInstantiationStrategy提供了根据反射和CGLIB创建对象实例的方法

public class SimpleInstantiationStrategy implements InstantiationStrategy {@Overridepublic Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) {if (bd.getMethodOverrides().isEmpty()) {Constructor<?> constructorToUse;synchronized (bd.constructorArgumentLock) {constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;if (constructorToUse == null) {final Class<?> clazz = bd.getBeanClass();if (clazz.isInterface()) {throw new BeanInstantiationException(clazz, "Specified class is an interface");}try {if (System.getSecurityManager() != null) {constructorToUse = AccessController.doPrivileged(new PrivilegedExceptionAction<Constructor<?>>() {@Overridepublic Constructor<?> run() throws Exception {return clazz.getDeclaredConstructor((Class[]) null);}});}else {//获取默认构造函数constructorToUse =  clazz.getDeclaredConstructor((Class[]) null);}bd.resolvedConstructorOrFactoryMethod = constructorToUse;}catch (Throwable ex) {throw new BeanInstantiationException(clazz, "No default constructor found", ex);}}}//创建对象return BeanUtils.instantiateClass(constructorToUse);}else {return instantiateWithMethodInjection(bd, beanName, owner);}}}

2.6 BeanUtils负责根据反射创建对象

public abstract class BeanUtils {public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {Assert.notNull(ctor, "Constructor must not be null");try {ReflectionUtils.makeAccessible(ctor);//通过反射创建对象return ctor.newInstance(args);}catch (InstantiationException ex) {throw new BeanInstantiationException(ctor, "Is it an abstract class?", ex);}catch (IllegalAccessException ex) {throw new BeanInstantiationException(ctor, "Is the constructor accessible?", ex);}catch (IllegalArgumentException ex) {throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", ex);}catch (InvocationTargetException ex) {throw new BeanInstantiationException(ctor, "Constructor threw exception", ex.getTargetException());}}}