Spring源码分析之IoC
IoC（Inversion of Controll）
一、概念
控制反转（Inversion of Control，缩写为IoC），是面向对象编程中的一种设计原则，可以用来减低计算机代码之间的耦合度。
Spring容器负责Bean的生命周期，通过DI（Dependency Injection）来向某个对象提供它所需的资源。
二、Spring容器 Factory
1、BeanFactory : 可以理解为一个HashMap，Key是BeanName ，value是Bean实例，通常只提供注册（put）和获取（get）操作，称之为简单容器
2、ApplicationContext ： VIP版本，高级容器。继承了多个接口，因此具备了更多的功能，如国际化，事件发布，多资源加载，系统环境等
三、源码分析
1、简单的Spring启动代码：
public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("classpath:applicationfile.xml"); }
2、在此方法中调用了refresh()
public ClassPathXmlApplicationContext( String[] configLocations, boolean refresh, @Nullable ApplicationContext parent) throws BeansException { super(parent); setConfigLocations(configLocations); if (refresh) { refresh(); } }
3、大致分为初始化容器和初始化Bean
@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.
// 初始化BeanFactory，并且加载注册BeanDefinition
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. // 设置 BeanFactory 的类加载器，添加几个 BeanPostProcessor，手动注册几个特殊的 bean prepareBeanFactory(beanFactory); try { // 【这里需要知道 BeanFactoryPostProcessor 这个知识点，Bean 如果实现了此接口， // 那么在容器初始化以后，Spring 会负责调用里面的 postProcessBeanFactory 方法。】 // 提供给子类的扩展点，到这里的时候，所有的 Bean 都加载、注册完成了，但是都还没有初始化 // 具体的子类可以在这步的时候添加一些特殊的 BeanFactoryPostProcessor 的实现类或做点什么事 // Allows post-processing of the bean factory in context subclasses. postProcessBeanFactory(beanFactory); // 调用 BeanFactoryPostProcessor 各个实现类的 postProcessBeanFactory(factory) 方法 // Invoke factory processors registered as beans in the context. invokeBeanFactoryPostProcessors(beanFactory); // 注册 BeanPostProcessor 的实现类，注意看和 BeanFactoryPostProcessor 的区别 // 此接口两个方法: postProcessBeforeInitialization 和 postProcessAfterInitialization // 两个方法分别在 Bean 初始化之前和初始化之后得到执行。注意，到这里 Bean 还没初始化 // Register bean processors that intercept bean creation. registerBeanPostProcessors(beanFactory); // 初始化当前 ApplicationContext 的 MessageSource，国际化这里就不展开说了，不然没完没了了 // Initialize message source for this context. initMessageSource(); // 初始化当前 ApplicationContext 的事件广播器，这里也不展开了 // Initialize event multicaster for this context. initApplicationEventMulticaster(); // 从方法名就可以知道，典型的模板方法(钩子方法)， // 具体的子类可以在这里初始化一些特殊的 Bean（在初始化 singleton beans 之前） // Initialize other special beans in specific context subclasses. onRefresh(); // 注册事件监听器，监听器需要实现 ApplicationListener 接口。这也不是我们的重点，过 // Check for listener beans and register them. registerListeners(); // 重点，重点，重点 // 初始化所有的 singleton beans //（lazy-init 的除外） // Instantiate all remaining (non-lazy-init) singletons. finishBeanFactoryInitialization(beanFactory); // 最后，广播事件，ApplicationContext 初始化完成 // Last step: publish corresponding event. finishRefresh(); } catch (BeansException ex) { if (logger.isWarnEnabled()) { logger.warn("Exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); } // 销毁已经初始化的 singleton 的 Beans，以免有些 bean 会一直占用资源 // 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(); } } }
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
Bean的形态: Resource > Document > Element > BeanDefinitonHolder (其中有属性BeanDefinition)
/** * Tell the subclass to refresh the internal bean factory. * @return the fresh BeanFactory instance * @see #refreshBeanFactory() * @see #getBeanFactory() */ protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { refreshBeanFactory(); return getBeanFactory(); }
/** * 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 { //查看当前ApplicationContext是否有BeanFactory，如果有就关闭 if (hasBeanFactory()) { destroyBeans(); closeBeanFactory(); } try { //初始化一个DefaultListableBeanFactory DefaultListableBeanFactory beanFactory = createBeanFactory(); beanFactory.setSerializationId(getId()); //设置BeanFactory的两个配置属性：是否允许Bean覆盖、是否允许循环依赖 customizeBeanFactory(beanFactory); //加载Bean到BeanFactory中 loadBeanDefinitions(beanFactory); synchronized (this.beanFactoryMonitor) { this.beanFactory = beanFactory; } } catch (IOException ex) { throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex); } }
/** * 通过XmlBeanDefinitionReader加载各个bean * 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); //重点 loadBeanDefinitions(beanDefinitionReader); }
/** * 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); } }
>>> 此处省略部分代码，直接跳重点
/** * 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 { //将XML转换为Document对象 Document doc = doLoadDocument(inputSource, resource); //重点 int count = registerBeanDefinitions(doc, resource); if (logger.isDebugEnabled()) { logger.debug("Loaded " + count + " bean definitions from " + resource); } return count; } ... }
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException { BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader(); int countBefore = getRegistry().getBeanDefinitionCount(); //重点 documentReader.registerBeanDefinitions(doc, createReaderContext(resource)); return getRegistry().getBeanDefinitionCount() - countBefore; }
@Override public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) { this.readerContext = readerContext; //从XML根节点开始解析文件 doRegisterBeanDefinitions(doc.getDocumentElement()); }
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); // 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; } } } preProcessXml(root); //重点 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)) { //解析default namespace下面的几个元素，包含import,alias,bean,beans四个标签 parseDefaultElement(ele, delegate); } else { //解析其他namespace的元素 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); } //解析bean标签 else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { processBeanDefinition(ele, delegate); } else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // recurse doRegisterBeanDefinitions(ele); } }
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { //将<bean/>节点中的信息提取出来，封装成BeanDefinitionHolder BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); if (bdHolder != null) { bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // Register the final decorated instance. 注册Bean BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry()); } catch (BeanDefinitionStoreException ex) { getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, ex); } // Send registration event. 注册完成，发送事件 getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder)); } }
public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { // Register bean definition under primary name. String beanName = definitionHolder.getBeanName(); //注册Bean 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); } } }
finishBeanFactoryInitialization(beanFactory);
@Override public void preInstantiateSingletons() throws BeansException { if (logger.isTraceEnabled()) { logger.trace("Pre-instantiating singletons in " + this); } // Iterate over a copy to allow for init methods which in turn register new bean definitions. // While this may not be part of the regular factory bootstrap, it does otherwise work fine. List<String> beanNames = new ArrayList<>(this.beanDefinitionNames); //初始化所有非懒加载的singleton beans // Trigger initialization of all non-lazy singleton beans... for (String beanName : beanNames) { RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); //不是抽象、并且单例、并且不是懒加载 if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { if (isFactoryBean(beanName)) { Object bean = getBean(FACTORY_BEAN_PREFIX + beanName); if (bean instanceof FactoryBean) { final FactoryBean<?> factory = (FactoryBean<?>) bean; boolean isEagerInit; if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) { isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit, getAccessControlContext()); } else { isEagerInit = (factory instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factory).isEagerInit()); } if (isEagerInit) { getBean(beanName); } } } else { getBean(beanName); } } } // Trigger post-initialization callback for all applicable beans... for (String beanName : beanNames) { Object singletonInstance = getSingleton(beanName); if (singletonInstance instanceof SmartInitializingSingleton) { final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance; if (System.getSecurityManager() != null) { AccessController.doPrivileged((PrivilegedAction<Object>) () -> { smartSingleton.afterSingletonsInstantiated(); return null; }, getAccessControlContext()); } else { smartSingleton.afterSingletonsInstantiated(); } } } }
直接跳到doGetBean
protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType, @Nullable final Object[] args, boolean typeCheckOnly) throws BeansException { //1、去除工厂前缀&,因为我们传递的不一定是BeanName也可能是aliasName final String beanName = transformedBeanName(name); Object bean; // Eagerly check singleton cache for manually registered singletons. //2、从单例缓存中获取Bean的三级缓存，这边涉及到解决Singleton循环依赖，待会儿再看 Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null) { if (logger.isTraceEnabled()) { if (isSingletonCurrentlyInCreation(beanName)) { logger.trace("Returning eagerly cached instance of singleton bean '" + beanName + "' that is not fully initialized yet - a consequence of a circular reference"); } else { logger.trace("Returning cached instance of singleton bean '" + beanName + "'"); } } //3、组装sharedInstance bean = getObjectForBeanInstance(sharedInstance, name, beanName, null); } else { // Fail if we're already creating this bean instance: // We're assumably within a circular reference. //4、如果该bean正在创建，抛出异常 if (isPrototypeCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } //如果单例模式中没有获取Bean则尝试从父类BeanFactory中获取 // Check if bean definition exists in this factory. //5、获取parentBeanFactory BeanFactory parentBeanFactory = getParentBeanFactory(); //6、parentBeanFactory 不为空且 beanDefinitionMap 中不存该 name 的 BeanDefinition if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { // Not found -> check parent. String nameToLookup = originalBeanName(name); //调用父类容器进行初始化 if (parentBeanFactory instanceof AbstractBeanFactory) { return ((AbstractBeanFactory) parentBeanFactory).doGetBean( nameToLookup, requiredType, args, typeCheckOnly); } else if (args != null) { // Delegation to parent with explicit args. return (T) parentBeanFactory.getBean(nameToLookup, args); } else if (requiredType != null) { // No args -> delegate to standard getBean method. return parentBeanFactory.getBean(nameToLookup, requiredType); } else { return (T) parentBeanFactory.getBean(nameToLookup); } } //7、如果typeCheckOnly==false，标记该bean被创建 if (!typeCheckOnly) { markBeanAsCreated(beanName); } try { //8、从容器中获取 beanName 相应的 GenericBeanDefinition 对象，并将其转换为 RootBeanDefinition 对象。如果传入的beanName是子对象，那么存在合并父对象的操作 final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); //9、检查给定的合并的 BeanDefinition checkMergedBeanDefinition(mbd, beanName, args); // Guarantee initialization of beans that the current bean depends on. 保证当前bean所依赖的bean的初始化 String[] dependsOn = mbd.getDependsOn(); if (dependsOn != null) { // 若给定的依赖 bean 已经注册为依赖给定的 bean // 即循环依赖的情况，抛出 BeanCreationException 异常 for (String dep : dependsOn) { if (isDependent(beanName, dep)) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'"); } //10、该映射关系保存到两个集合中：dependentBeanMap、dependenciesForBeanMap registerDependentBean(dep, beanName); try { getBean(dep); } catch (NoSuchBeanDefinitionException ex) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "'" + beanName + "' depends on missing bean '" + dep + "'", ex); } } } // Create bean instance. if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, () -> { try { // 重中之重 return createBean(beanName, mbd, args); } catch (BeansException ex) { // Explicitly remove instance from singleton cache: It might have been put there // eagerly by the creation process, to allow for circular reference resolution. // Also remove any beans that received a temporary reference to the bean. destroySingleton(beanName); throw ex; } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } else if (mbd.isPrototype()) { // It's a prototype -> create a new instance. 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, () -> { 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; } } // Check if required type matches the type of the actual bean instance. if (requiredType != null && !requiredType.isInstance(bean)) { try { T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType); if (convertedBean == null) { throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); } return convertedBean; } catch (TypeMismatchException ex) { if (logger.isTraceEnabled()) { logger.trace("Failed to convert bean '" + name + "' to required type '" + ClassUtils.getQualifiedName(requiredType) + "'", ex); } throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); } } return (T) bean; }
@Override protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException { if (logger.isTraceEnabled()) { logger.trace("Creating instance of bean '" + beanName + "'"); } RootBeanDefinition mbdToUse = mbd; // Make sure bean class is actually resolved at this point, and // clone the bean definition in case of a dynamically resolved Class // which cannot be stored in the shared merged bean definition. //<1> 确保此时的 bean 已经被解析了 Class<?> resolvedClass = resolveBeanClass(mbd, beanName); if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) { mbdToUse = new RootBeanDefinition(mbd); mbdToUse.setBeanClass(resolvedClass); } // Prepare method overrides. try { //验证和准备覆盖方法 mbdToUse.prepareMethodOverrides(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(), beanName, "Validation of method overrides failed", ex); } try { // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance. // 实例化前置准备,给 BeanPostProcessors 一个机会用来返回一个代理类而不是真正的类实例 // AOP 的功能就是基于这个地方 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); } try { //创建 Bean 对象 Object beanInstance = doCreateBean(beanName, mbdToUse, args); if (logger.isTraceEnabled()) { logger.trace("Finished creating instance of bean '" + beanName + "'"); } return beanInstance; } catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) { // A previously detected exception with proper bean creation context already, // or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry. throw ex; } catch (Throwable ex) { throw new BeanCreationException( mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex); } }
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args) throws BeanCreationException { // Instantiate the bean. BeanWrapper instanceWrapper = null; // <1> 单例模型，则从未完成的 FactoryBean 缓存中删除 if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } // <2> 使用合适的实例化策略来创建新的实例：工厂方法、构造函数自动注入、简单初始化 if (instanceWrapper == null) { instanceWrapper = createBeanInstance(beanName, mbd, args); } // 包装的实例对象 final Object bean = instanceWrapper.getWrappedInstance(); //包装的实例的类型 Class<?> beanType = instanceWrapper.getWrappedClass(); if (beanType != NullBean.class) { mbd.resolvedTargetType = beanType; } // Allow post-processors to modify the merged bean definition. //如果有后置处理器则允许修改bean definition 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; } } // Eagerly cache singletons to be able to resolve circular references // even when triggered by lifecycle interfaces like BeanFactoryAware. //单例模式 循环依赖的标志位 boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName)); if (earlySingletonExposure) { if (logger.isTraceEnabled()) { logger.trace("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references"); } //将该beanFactory加入到singletonFactories中 addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); } // Initialize the bean instance. Object exposedObject = bean; try { // <5> 对 bean 进行填充，将各个属性值注入，其中，可能存在依赖于其他 bean 的属性 // 则会递归初始依赖 bean populateBean(beanName, mbd, instanceWrapper); //初始化bean,如init-method，InitializingBean ，BeanPostProcessor 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); } } //处理循环依赖 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<>(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 " + "'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example."); } } } } // Register bean as disposable. //注册bean try { registerDisposableBeanIfNecessary(beanName, bean, mbd); } catch (BeanDefinitionValidationException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex); } return exposedObject; }
流程 ：
1、instanceWrapper = createBeanInstance(beanName, mbd, args)
2、final Object bean = instanceWrapper.getWrappedInstance();
3、使用依赖注入DI填充属性 populateBean(beanName, mbd, instanceWrapper);
4、Object exposedObject = bean;
5、初始化Bean ：exposedObject = initializeBean(beanName, exposedObject, mbd);
5.1、激活Aware ： invokeAwareMethods(beanName, bean)
5.2、实现BeanPostProcessor 的 postProcessBeforeInitialization 回调 ： wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
5.3、afterPropertiesSet 、 initMethod 回调 ： invokeInitMethods(beanName, wrappedBean, mbd);
5.4、BeanPostProcessorsAfterInitialization回调 ： wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
6、注册Bean ：registerDisposableBeanIfNecessary(beanName, bean, mbd);
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