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前言

基于源碼 springboot2.7.3，對應 spring5.3.22
本章源碼只注釋 AbstractApplicationContext#refresh 方法

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一、AbstractApplicationContext#refresh 方法解析

1.1 前置

Spring 的大致流程是先將 Bean 讀取成 BeanDefinition，然后再實例化 bean，初始化Bean
無論是使用注解還是 XML 配置的方式，都會將 Bean 解析成 BeanDefinition， XML解析的核心類是 XmlBeanDefinitionReader

1.2 refresh 方法

模板方法，里面大量的擴展點可交由子類實現

// 刷新前的操作prepareRefresh();// Tell the subclass to refresh the internal bean factory.// 獲取 BeanFactoryConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();// Prepare the bean factory for use in this context.// 預處理 beanFactory// 向 beanFactory 添加了一些 ignoreDependencyInterfaceprepareBeanFactory(beanFactory);try {// Allows post-processing of the bean factory in context subclasses.// 交由子類實現, 在刷新前對 beanFactory 做一些操作postProcessBeanFactory(beanFactory);StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");// Invoke factory processors registered as beans in the context.// 執行 BFPPinvokeBeanFactoryPostProcessors(beanFactory);// Register bean processors that intercept bean creation.// 注冊 BPPregisterBeanPostProcessors(beanFactory);beanPostProcess.end();// Initialize message source for this context.// 初始化 MessageSource, i18n 相關initMessageSource();// Initialize event multicaster for this context.// 初始化事件發布器initApplicationEventMulticaster();// Initialize other special beans in specific context subclasses.// 刷新容器onRefresh();// Check for listener beans and register them.// 注冊事件監聽器registerListeners();// Instantiate all remaining (non-lazy-init) singletons.// 重要, 完成 bean 的初始化工作finishBeanFactoryInitialization(beanFactory);// Last step: publish corresponding event.// 結束刷新finishRefresh();

1.2.1 prepareRefresh

protected void prepareRefresh() {// Switch to active.this.startupDate = System.currentTimeMillis();this.closed.set(false);this.active.set(true);// ... 日志打印// Initialize any placeholder property sources in the context environment.// 初始化 PropertySources, 如果是 servlet 應用的話, 會將 ServletContext 的配置信息放入到 Environment 中initPropertySources();// Validate that all properties marked as required are resolvable:// see ConfigurablePropertyResolver#setRequiredProperties// 如果有必須的配置, 驗證配置是否存在getEnvironment().validateRequiredProperties();// Store pre-refresh ApplicationListeners...// earlyApplicationListeners：提前暴露的 Listener// 兼容 SpringBootif (this.earlyApplicationListeners == null) {this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);}else {// Reset local application listeners to pre-refresh state.this.applicationListeners.clear();this.applicationListeners.addAll(this.earlyApplicationListeners);}// Allow for the collection of early ApplicationEvents,// to be published once the multicaster is available...this.earlyApplicationEvents = new LinkedHashSet<>();
}

1.2.2 obtainFreshBeanFactory

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {// 刷新 beanFactory// 交由子類實現的方法// 1. 如果是 Spring 應用, 則是 AbstractRefreshableApplicationContext, 會創建 beanFactory// 2. 如果是 SpringBoot 應用, 實現類則是 GenericApplicationContext, beanFactory 已經提前創建好了, 直接獲取出來refreshBeanFactory();return getBeanFactory();
}

1.2.3 prepareBeanFactory

對 BeanFactory 做一些前置處理

// 1. ignoreDependencyInterface
// 2. registerResolvableDependency
// 3. 將 environment、System、ApplicationSetup 等 Bean 加入到 beaFactory
// 4. 將 ApplicationContext(this) 注冊到 BeanFactory

1.2.4 postProcessBeanFactory

鉤子, 交給子類實現，這里看 SpringBoot 的實現

@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {// 添加了一個 BPPbeanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));beanFactory.ignoreDependencyInterface(ServletContextAware.class);// 將 Request 和 Session 兩個 Scope 注冊到 ApplicationContextregisterWebApplicationScopes();
}

1.2.5 invokeBeanFactoryPostProcessors

執行 BFPP

1. BFPP 主要分為兩種，一種是 BeanDefinitionRegistryPostProcessor，這個類可以用來注冊 BeanDefinition，而新注冊的 BeanDefinition 也可能是一個 BeanDefinitionRegistryPostProcessor，另外一種就只是 BFPP
2. BFPP 的優先級 使用 applicationContext 直接注冊的 > @PriorityOrder > @Order > 普通的

public static void invokeBeanFactoryPostProcessors(  ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPos tProcessor> beanFactoryPostProcessors) {  // beanFactory 一般是 DefaultListableBeanFactory, 它確實是一個 BeanDefinitionRegistryif (beanFactory instanceof BeanDefinitionRegistry) {  BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; // 常規的 BFPP List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>(); // 能夠注冊 bean 的 BFPPList<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();  for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {  if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {  BeanDefinitionRegistryPostProcessor registryProcessor =  (BeanDefinitionRegistryPostProcessor) postProcessor;  // 調用 postProcessBeanDefinitionRegistry，注冊 beanregistryProcessor.postProcessBeanDefinitionRegistry(registry);  registryProcessors.add(registryProcessor);  }  else {  regularPostProcessors.add(postProcessor);  }  }  // 從容器中獲取所有的 BeanDefinitionRegistryPostProcessorString[] postProcessorNames =  beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);  for (String ppName : postProcessorNames) {  if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {  currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));  processedBeans.add(ppName);  }  }  sortPostProcessors(currentRegistryProcessors, beanFactory);  registryProcessors.addAll(currentRegistryProcessors);  invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());  currentRegistryProcessors.clear();  // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.  postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);  for (String ppName : postProcessorNames) {  if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {  currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));  processedBeans.add(ppName);  }  }  sortPostProcessors(currentRegistryProcessors, beanFactory);  registryProcessors.addAll(currentRegistryProcessors);  invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());  currentRegistryProcessors.clear();  // 這里為什么要用 while? 因為 BeanDefinitionRegistryPostProcessor 還有可能注冊 BeanDefinitionRegistryPostProcessorsboolean reiterate = true;  while (reiterate) {  reiterate = false;  postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);  for (String ppName : postProcessorNames) {  if (!processedBeans.contains(ppName)) {  currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));  processedBeans.add(ppName);  reiterate = true;  }  }  sortPostProcessors(currentRegistryProcessors, beanFactory);  registryProcessors.addAll(currentRegistryProcessors);  invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());  currentRegistryProcessors.clear();  }  // Now, invoke the postProcessBeanFactory callback of all processors handled so far.  // 執行 register 的 postProcessorinvokeBeanFactoryPostProcessors(registryProcessors, beanFactory);  // 然后執行參數中傳過來的 bfpp 的 postProcessor// 注意：這里只處理參數傳過來的 BFPPinvokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);  }  else {  // Invoke factory processors registered with the context instance.  invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);  }  // 下面將會執行容器中所有的 BFPPbeanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);  // 1. 標注了 @PriorityOrdered 的 BFPPList<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();  // 2. 標注了 @Order 的 BFPPList<String> orderedPostProcessorNames = new ArrayList<>();  // 3. 普通的 BFPPList<String> nonOrderedPostProcessorNames = new ArrayList<>();  for (String ppName : postProcessorNames) {  if (processedBeans.contains(ppName)) {  // skip - already processed in first phase above  }  else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {  priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));  }  else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {  orderedPostProcessorNames.add(ppName);  }  else {  nonOrderedPostProcessorNames.add(ppName);  }  }  // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.  sortPostProcessors(priorityOrderedPostProcessors, beanFactory);  invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);  // Next, invoke the BeanFactoryPostProcessors that implement Ordered.  List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());  for (String postProcessorName : orderedPostProcessorNames) {  orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));  }  sortPostProcessors(orderedPostProcessors, beanFactory);  invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);  // Finally, invoke all other BeanFactoryPostProcessors.  List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());  for (String postProcessorName : nonOrderedPostProcessorNames) {  nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));  }  invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);  // Clear cached merged bean definitions since the post-processors might have  // modified the original metadata, e.g. replacing placeholders in values...    beanFactory.clearMetadataCache();  
}

1.2.6 registerBeanPostProcessors

注冊 BPP
優先級 @PriorityOrdered > Ordered > 普通的

public static void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {// 獲取所有的 BPPString[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);// BPP的數量，這里 +1 是因為下面要加一個int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));// 1. PriorityOrdered 的 BPPList<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();// 2. 內部的 BPPList<BeanPostProcessor> internalPostProcessors = new ArrayList<>();// 3. Ordered 的 BPPList<String> orderedPostProcessorNames = new ArrayList<>();// 4. 普通的 BPPList<String> nonOrderedPostProcessorNames = new ArrayList<>();for (String ppName : postProcessorNames) {if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);priorityOrderedPostProcessors.add(pp);// 實現了 MergedBeanDefinitionPostProcessor 為內部的 BPPif (pp instanceof MergedBeanDefinitionPostProcessor) {internalPostProcessors.add(pp);}}else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {orderedPostProcessorNames.add(ppName);}else {nonOrderedPostProcessorNames.add(ppName);}}// PriorityOrdered 的 BPP 排序sortPostProcessors(priorityOrderedPostProcessors, beanFactory);registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);// Next, register the BeanPostProcessors that implement Ordered.// Ordered 的 BPP 排序List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());for (String ppName : orderedPostProcessorNames) {BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);orderedPostProcessors.add(pp);if (pp instanceof MergedBeanDefinitionPostProcessor) {internalPostProcessors.add(pp);}}sortPostProcessors(orderedPostProcessors, beanFactory);registerBeanPostProcessors(beanFactory, orderedPostProcessors);// 普通的 BPP 排序List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());for (String ppName : nonOrderedPostProcessorNames) {BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);nonOrderedPostProcessors.add(pp);if (pp instanceof MergedBeanDefinitionPostProcessor) {internalPostProcessors.add(pp);}}registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);// Finally, re-register all internal BeanPostProcessors.sortPostProcessors(internalPostProcessors, beanFactory);registerBeanPostProcessors(beanFactory, internalPostProcessors);beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

1.2.7 initApplicationEventMulticaster

初始化事件發布器, 用來發布各種事件
默認對象為 SimpleApplicationEventMulticaster

protected void initApplicationEventMulticaster() {ConfigurableListableBeanFactory beanFactory = getBeanFactory();// 如果容器中有了, 使用容器中的if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {this.applicationEventMulticaster =beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);if (logger.isTraceEnabled()) {logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");}}else {// 沒有這里創建一個this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);if (logger.isTraceEnabled()) {logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");}}
}

1.2.8 onRefresh

交由子類實現的鉤子

1.2.9 registerListeners

注冊監聽器

protected void registerListeners() {// 1. 獲取直接注冊到 applicationContext 中的 Listernerfor (ApplicationListener<?> listener : getApplicationListeners()) {getApplicationEventMulticaster().addApplicationListener(listener);}// 2. 獲取容器中所有的 ApplicationListenerString[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);for (String listenerBeanName : listenerBeanNames) {getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);}// Publish early application events now that we finally have a multicaster...Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;this.earlyApplicationEvents = null;if (!CollectionUtils.isEmpty(earlyEventsToProcess)) {for (ApplicationEvent earlyEvent : earlyEventsToProcess) {getApplicationEventMulticaster().multicastEvent(earlyEvent);}}
}

1.2.10 finishBeanFactoryInitialization

完成 bean 的初始化, Bean 的創建過程就在這個方法里
內容太多，請查看 1.3 章節

1.2.11 finishRefresh

結束 refresh 方法

protected void finishRefresh() {// 清理緩存clearResourceCaches();// 向容器中添加一個 DefaultLifecycleProcessorinitLifecycleProcessor();// 調用 LifecycleProcessor 的 onRefresh() 方法getLifecycleProcessor().onRefresh();// Publish the final event.publishEvent(new ContextRefreshedEvent(this));// Participate in LiveBeansView MBean, if active.if (!NativeDetector.inNativeImage()) {LiveBeansView.registerApplicationContext(this);}
}

1.3 Bean 的生命周期

1.3.1 入口

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {// 。。。// 凍結 BeanFactroy, 就是設置為一個標志位beanFactory.freezeConfiguration();// 實例化 beanbeanFactory.preInstantiateSingletons();
}

1.3.2 preInstantiateSingletons

代碼太多了，直接寫核心流程

// preInstantiateSingletons()
// 1. 處理 FactoryBean
// 2. 調用 getBean()

1.3.3 doGetBean

// 1. 處理 dependsOn
// 2. 處理單實例 bean, 調用 createBean
// 3. 處理 Prototype Bean
// 4. 處理別的 Scope 的 Bean, 例如 request, Session, 擴展: Nacos 的 @RefreshScope 也是這里處理的

1.3.4 createBean

// 1. 處理方法覆蓋
mbdToUse.prepareMethodOverrides();
// 2. 調用 InstantiationAwareBeanPostProcessors 的 applyBeanPostProcessorsBeforeInstantiation() 方
// 2.1 如果這個方法返回了一個Bean, 則說明是我們自主控制了 Bean 的創建, 后續流程將不再執行
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {return bean;
}
// 3. 調用 doCreateBean() 方法創建 Bean
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);

1.3.5 doCreateBean

protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)throws BeanCreationException {// Instantiate the bean.BeanWrapper instanceWrapper = null;if (mbd.isSingleton()) {instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);}// 創建 Bean 實例// 1. 使用 Supplier 創建// 2. 使用 工廠方法創建// 3. 使用構造器創建if (instanceWrapper == null) {instanceWrapper = createBeanInstance(beanName, mbd, args);}Object bean = instanceWrapper.getWrappedInstance();Class<?> beanType = instanceWrapper.getWrappedClass();// 。。。// 判斷是否允許提前暴露對象boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&isSingletonCurrentlyInCreation(beanName));if (earlySingletonExposure) {// 添加到三級緩存中// getEarlyBeanReference() 會調用 InstantiationAwareBeanPostProcessor 的 getEarlyBeanReference() 方法// 1. InstantiationAwareBeanPostProcessor 需要注意一個實現類 AbstractAutoProxyCreator, 這個類是用來創建動態代理對象的addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));}// 對外暴露的對象Object exposedObject = bean;try {// 填充 bean 屬性populateBean(beanName, mbd, instanceWrapper);// 初始化 beanexposedObject = initializeBean(beanName, exposedObject, mbd);}// ...// 注冊 DisposableBeantry {registerDisposableBeanIfNecessary(beanName, bean, mbd);}/。。。return exposedObject;
}

1.3.6 populateBean

// 1. 執行 InstantiationAwareBeanPostProcessor#postProcessAfterInstantiation
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {if (!bp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {return;}}
}
// 2. 處理 BeanDefinition 的 propertyValues

1.3.7 initializeBean 初始化 bean

// 1. 執行 Aware
// 1.1 這里只處理 BeanNameAware,BeanClassLoaderAware,BeanFactoryAware
invokeAwareMethods(beanName, bean);
// 2. 調用 BPP 的 postProcessBeforeInitialization()
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
// 3. 調用初始化方法
// 3.1 InitializingBean 調用 afterPropertiesSet()
// 3.2 調用我們自定義的初始化方法
invokeInitMethods(beanName, wrappedBean, mbd);
// 調用  BPP 的 postProcessAfterInitialization()
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);

二、各種 BeanPostProcessor(BPP)

在 Bean 的生命周期中常見的可分為 4 種 BPP，可以查看類 BeanPostProcessorCache，不同的 BPP 在 Bean 的生命周期的不同時刻執行。

1. InstantiationAwareBeanPostProcessor
2. SmartInstantiationAwareBeanPostProcessor
3. DestructionAwareBeanPostProcessor
4. MergedBeanDefinitionPostProcessor

InstantiationAwareBeanPostProcessor

Bean的生命周期中一定是先實例化再初始化。

@Component
public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor {/*** 實例化之前, 如果這里返回了一個 bean 說明我們需要自主控制 bean 的生命周期* 將不再執行后面的 BPP 和初始化操作*/@Overridepublic Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {return null;}/*** 實例化之后, 只有 before 方法返回的不是一個 null, 才會執行此方法*/@Overridepublic boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {return true;}/*** Bean 執行 afterProperties 的時候調用，可以用來修改屬性綁定* 但是這種并不能用來處理解密數據庫連接, 因為這個流程太過于前置了, bean 還沒有將加密的值綁定上, 這里獲取不到加密的值當然無法解密*/@Overridepublic PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) throws BeansException {if (bean instanceof BppBean) {MutablePropertyValues mpvs = (pvs instanceof MutablePropertyValues) ?(MutablePropertyValues) pvs : new MutablePropertyValues();// 會將 name 屬性值修改為 abcmpvs.add("name", "abc");return mpvs;}return pvs;}/*** 跟上面方法功能一樣, 但是這個方法將要被廢棄* 如果 postProcessProperties 返回 null, 則會調用這個方法*/@Overridepublic PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {return pvs;}
}

MergedBeanDefinitionPostProcessor

該接口可以用來操作 BeanDefinition

@Override
public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {}

SmartInstantiationAwareBeanPostProcessor

繼承了 InstantiationAwareBeanPostProcessor

@Component
public class MySmartInstantiationAwareBeanPostProcessor implements SmartInstantiationAwareBeanPostProcessor {/*** 提前預測 bean 類型* 返回 null 表示不預測*/public Class<?> predictBeanType(Class<?> beanClass, String beanName) throws BeansException {if (beanName.equalsIgnoreCase("bppBean")) {return BppBean.class;}return null;}/*** 可以用來指定創建 bean 所用的構造器*/@Overridepublic Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, String beanName) throws BeansException {return SmartInstantiationAwareBeanPostProcessor.super.determineCandidateConstructors(beanClass, beanName);}/*** 如果 bean 從三級緩存中獲取對象, 則會調用這個方法*/@Overridepublic Object getEarlyBeanReference(Object bean, String beanName) throws BeansException {return bean;}
}

DestructionAwareBeanPostProcessor

Bean 銷毀前執行

@Component
public class MyDestructionAwareBeanPostProcessor implements DestructionAwareBeanPostProcessor {/*** 銷毀之前執行*/@Overridepublic void postProcessBeforeDestruction(Object bean, String beanName) throws BeansException {System.out.println(beanName + "銷毀之前執行");}/*** false 表示不執行銷毀*/@Overridepublic boolean requiresDestruction(Object bean) {return false;}
}

總結

博主對源碼的理解也很淺顯，如有異議，可于評論區留言，歡迎各位大佬指教。

Bean 的生命周期

getBean() -> doGetBean() -> createBean() -> doCreateBean()

1. preInstantiateSingletons
1.1 處理 FactoryBean
1.2 調用 getBean()2. getBean()
2.1 調用 doGetBean()3. doGetBean()
3.1 處理 DependsOn
3.2 獲取單實例 Bean 調用 createBean()
3.3 獲取多實例 Bean
3.4 處理別的 Scope 類型的Bean, 如 Request，Session4. createBean()
4.1 處理方法覆蓋
4.2 調用 InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation
4.2.1 如果這里返回了一個Bean 將會調用 BeanPostProcessor#postProcessAfterInitialization。
4.2.2 然后后續的流程將不再處理，直接返回4.2.1 返回的 bean
4.3 調用 doCreateBean() 創建 Bean5. doCreateBean()
5.1 調用 `createBeanInstance` 創建 bean
5.1.1 使用 Supplier 創建 Bean
5.1.2 使用工廠方法創建 Bean
5.1.3 使用構造器創建 Bean5.2 調用 populateBean
5.2.1 調用 InstantiationAwareBeanPostProcessor#postProcessAfterInstantiation
5.2.2 處理 BeanDefinition 的 PropertyValues5.3 初始化 initializeBean
5.3.1 執行 Aware; BeanNameAware, BeanClassLoaderAware, BeanFactoryAware
5.3.2 執行 BeanPostProcessor#postProcessBeforeInitialization
5.3.3 執行初始化方法  invokeInitMethods()5.4 invokeInitMethods()
5.4.1 如果是 InitializingBean 執行 afterPropertiesSet
5.4.2 執行自定義的初始化方法