Spring創(chuàng)建Bean的過程Debug
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? 作者?|??x1aoda1
來源 |? urlify.cn/QzYFba
Spring流程Debug
1.1 Spring測試環(huán)境搭建
Spring模塊概覽，綠色是模塊，Spring中八大模塊，黑色表示該模塊包含的jar包（組件）。例如我們想要用IOC容器，也就是綠色的CoreContainer，我們需要導(dǎo)入Beans，Core,Context,SpEL（spring-expression）四個包。
Test：測試相關(guān)
Core Container：IOC容器
AOP：面向切面編程
Aspects：切面
Instrumenttation：跟JDK關(guān)聯(lián)，一般不用
Messaging：消息服務(wù)，一般不用
Data Access/Integration：數(shù)據(jù)訪問與集成（JDBC訪問，Transaction事務(wù)，ORM對象關(guān)系映射，OXM和XML映射一般不用，JMS為Java消息服務(wù)Java-message-service一般不用）
Web：Web服務(wù)（WebSocket網(wǎng)絡(luò)通信協(xié)議，Servlet, Web，Portlet一般不用）
最偷懶的方式，是直接導(dǎo)入Spring-Framework。但是可能導(dǎo)入不必要的包，導(dǎo)致項目打包后比較大
由于Spring-Content中的ApplicationContent是整個IOC的入口。我們導(dǎo)入Spring-context包即可
????org.springframework
????spring-context
????5.2.3.RELEASE
我們導(dǎo)入spring-content后，默認(rèn)會導(dǎo)入該組件的依賴jar，spring-content底層的依賴可以看到，實際上我們是導(dǎo)入了Core Container模塊：
??
????
??????org.springframework
??????spring-aop
??????5.2.3.RELEASE
??????compile
????
????
??????org.springframework
??????spring-beans
??????5.2.3.RELEASE
??????compile
????
????
??????org.springframework
??????spring-core
??????5.2.3.RELEASE
??????compile
????
????
??????org.springframework
??????spring-expression
??????5.2.3.RELEASE
??????compile
????
??
新建Spring配置文件spring.xml：
"1.0"?encoding="UTF-8"?>
"http://www.springframework.org/schema/beans"
???????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
???????xsi:schemaLocation="http://www.springframework.org/schema/beans?http://www.springframework.org/schema/beans/spring-beans.xsd">
????
????
????"hello"?class="com.xiaodai.service.Hello">
????????
????????"id"?value="1">
????????"name"?value="zhangsan">
????????"age"?value="18">
????
編寫測試類：
import?com.xiaodai.service.Hello;
import?org.springframework.context.ApplicationContext;
import?org.springframework.context.support.ClassPathXmlApplicationContext;
public?class?Test?{
????public?static?void?main(String[]?args)?{
????????ApplicationContext?applicationContext?=?new?ClassPathXmlApplicationContext("spring.xml");
????????Hello?hello?=?applicationContext.getBean("hello",?Hello.class);
????????System.out.println(hello.getName());
????}
}
1.2 Debug容器創(chuàng)建過程
從測試類的new ClassPathXmlApplicationContext("spring.xml")開始debug，進(jìn)入ClassPathXmlApplicationContext，可以看到:
?public?ClassPathXmlApplicationContext(
???String[]?configLocations,?boolean?refresh,?@Nullable?ApplicationContext?parent)
???throws?BeansException?{
??super(parent);
??//?設(shè)置配置文件路徑
??setConfigLocations(configLocations);
??if?(refresh)?{
??????????//?核心步驟
???refresh();
??}
?}
加載配置文件后，進(jìn)入refresh()方法，該方法是容器初始化的核心步驟。該方法包含十三個方法：
????????@Override
?public?void?refresh()?throws?BeansException,?IllegalStateException?{
??synchronized?(this.startupShutdownMonitor)?{
???//?Prepare?this?context?for?refreshing.
???/**?
????*?準(zhǔn)備刷新，做一些最基本的準(zhǔn)備化工作
???**/
???prepareRefresh();
???//?Tell?the?subclass?to?refresh?the?internal?bean?factory.
???/**?
????*?獲得一個刷新的bean容器，實質(zhì)就是獲取工廠。
????*?加載xml等配置文件，用該文件產(chǎn)生的BeanDefinition來創(chuàng)建一個工廠
???**/
???ConfigurableListableBeanFactory?beanFactory?=?obtainFreshBeanFactory();
???//?Prepare?the?bean?factory?for?use?in?this?context.
???/**
????*?準(zhǔn)備bean工廠
???**/
???prepareBeanFactory(beanFactory);
???try?{
????//?Allows?post-processing?of?the?bean?factory?in?context?subclasses.
????//?后置增強，方便擴(kuò)展
????postProcessBeanFactory(beanFactory);
????//?Invoke?factory?processors?registered?as?beans?in?the?context.
????//?實例化并且執(zhí)行BeanFactoryPostProcessors
????invokeBeanFactoryPostProcessors(beanFactory);
????//?Register?bean?processors?that?intercept?bean?creation.
????//?實例化并且注冊所有的BeanPostProcessor
????registerBeanPostProcessors(beanFactory);
????//?Initialize?message?source?for?this?context.
????//?國際化設(shè)置，一般用不到
????initMessageSource();
????//?Initialize?event?multicaster?for?this?context.
????//?初始化應(yīng)用程序的多波器和廣播器
????initApplicationEventMulticaster();
????//?Initialize?other?special?beans?in?specific?context?subclasses.
????//?空方法，預(yù)留給子類做擴(kuò)展
????onRefresh();
????//?Check?for?listener?beans?and?register?them.
????//?注冊監(jiān)聽器
????registerListeners();
????//?Instantiate?all?remaining?(non-lazy-init)?singletons.
????//?工作中常用，面試常問。實例化所有非懶加載的實例對象
????finishBeanFactoryInitialization(beanFactory);
????//?Last?step:?publish?corresponding?event.
????//?完成刷新
????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();
???}
??}
?}
1.3 AbstractApplicationContext的refresh()包含的13個方法分析
結(jié)合概覽圖一個一個方法分析：
方法1：prepareRefresh() => 準(zhǔn)備工作
準(zhǔn)備刷新，做一些最基本的準(zhǔn)備化工作
?protected?void?prepareRefresh()?{
??//?Switch?to?active.
??//?設(shè)置開始時間
??this.startupDate?=?System.currentTimeMillis();
??//?關(guān)閉狀態(tài)設(shè)置為false
??this.closed.set(false);
??//?活躍狀態(tài)設(shè)置為true
??this.active.set(true);
????????//?打印日志
??if?(logger.isDebugEnabled())?{
???if?(logger.isTraceEnabled())?{
????logger.trace("Refreshing?"?+?this);
???}
???else?{
????logger.debug("Refreshing?"?+?getDisplayName());
???}
??}
??//?Initialize?any?placeholder?property?sources?in?the?context?environment.
??//?初始化屬性資源
??initPropertySources();
??//?Validate?that?all?properties?marked?as?required?are?resolvable:
??//?see?ConfigurablePropertyResolver#setRequiredProperties
??//?獲取環(huán)境信息，驗證屬性信息
??getEnvironment().validateRequiredProperties();
??//?Store?pre-refresh
??//?存儲預(yù)刷新的一些應(yīng)用信息的監(jiān)聽器
??ApplicationListeners...
??if?(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...
??//?創(chuàng)建一些監(jiān)聽器事件的集合
??this.earlyApplicationEvents?=?new?LinkedHashSet<>();
?}
總結(jié)：1.設(shè)置啟動事件 2.設(shè)置關(guān)閉活躍的狀態(tài) 3.獲取環(huán)境對象并設(shè)置屬性值 4.設(shè)置監(jiān)聽器以及需要發(fā)布事件的集合
重要的點：
獲取環(huán)境信息，驗證屬性信息，getEnvironment().validateRequiredProperties();
存儲預(yù)刷新的一些應(yīng)用信息的監(jiān)聽器，在Spring中是空實現(xiàn)，但是SpringBoot中，是有具體的值的
方法2：obtainFreshBeanFactory() => 獲得一個刷新的bean容器
獲得一個刷新的bean容器，實質(zhì)就是獲取工廠。創(chuàng)建容器對象DefaultListableBeanFactory;加載xml配置文件的屬性到當(dāng)前的工廠中，最重要的就是BeanDefinition
AbstractRefreshableApplicationContext:
????//?只要進(jìn)到這個方法，那么我們創(chuàng)建的一定是一個新的工廠
?@Override
?protected?final?void?refreshBeanFactory()?throws?BeansException?{
??if?(hasBeanFactory())?{
??????//?如果存在先銷毀，后關(guān)閉
???destroyBeans();
???closeBeanFactory();
??}
??try?{
??????//?創(chuàng)建bean工廠，這里使用的就是DefaultListableBeanFactory。此時創(chuàng)建的工廠里面的屬性值都是默認(rèn)值
???DefaultListableBeanFactory?beanFactory?=?createBeanFactory();
???//?序列化id
???beanFactory.setSerializationId(getId());
???//?設(shè)置一些屬性值
???customizeBeanFactory(beanFactory);
???//?加載bean的定義屬性值。該方法有很多重載，非常復(fù)雜，核心是do操作
???//?完成配置文件或者配置類文件的加載
???loadBeanDefinitions(beanFactory);
???synchronized?(this.beanFactoryMonitor)?{
????this.beanFactory?=?beanFactory;
???}
??}
??catch?(IOException?ex)?{
???throw?new?ApplicationContextException("I/O?error?parsing?bean?definition?source?for?"?+?getDisplayName(),?ex);
??}
?}
方法3：prepareBeanFactory(beanFactory) => 準(zhǔn)備（初始化）Bean工廠
為方法2拿到的工廠，設(shè)置某些具體的值
?protected?void?prepareBeanFactory(ConfigurableListableBeanFactory?beanFactory)?{
??//?Tell?the?internal?bean?factory?to?use?the?context's?class?loader?etc.
??//?為bean工廠設(shè)置類加載器
??beanFactory.setBeanClassLoader(getClassLoader());
??//?設(shè)置SPEL解析器
??beanFactory.setBeanExpressionResolver(new?StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
??beanFactory.addPropertyEditorRegistrar(new?ResourceEditorRegistrar(this,?getEnvironment()));
??//?Configure?the?bean?factory?with?context?callbacks.
??//?添加一個BeanPostProcessor
??beanFactory.addBeanPostProcessor(new?ApplicationContextAwareProcessor(this));
??//?忽略對應(yīng)接口的實現(xiàn)
??beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
??beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
??beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
??beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
??beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
??beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
??//?BeanFactory?interface?not?registered?as?resolvable?type?in?a?plain?factory.
??//?MessageSource?registered?(and?found?for?autowiring)?as?a?bean.
????????//?注冊一些依賴
??beanFactory.registerResolvableDependency(BeanFactory.class,?beanFactory);
??beanFactory.registerResolvableDependency(ResourceLoader.class,?this);
??beanFactory.registerResolvableDependency(ApplicationEventPublisher.class,?this);
??beanFactory.registerResolvableDependency(ApplicationContext.class,?this);
??//?Register?early?post-processor?for?detecting?inner?beans?as
??//?ApplicationListeners添加一個BeanPostProcessor增強器
??ApplicationListeners.
??beanFactory.addBeanPostProcessor(new?ApplicationListenerDetector(this));
??//?Detect?a?LoadTimeWeaver?and?prepare?for?weaving,?if?found.
??if?(beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME))?{
???beanFactory.addBeanPostProcessor(new?LoadTimeWeaverAwareProcessor(beanFactory));
???//?Set?a?temporary?ClassLoader?for?type?matching.
???beanFactory.setTempClassLoader(new?ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
??}
??//?Register?default?environment?beans.
??if?(!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME))?{
???beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME,?getEnvironment());
??}
??if?(!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME))?{
???beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME,?getEnvironment().getSystemProperties());
??}
??if?(!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME))?{
???beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME,?getEnvironment().getSystemEnvironment());
??}
?}
方法4：postProcessBeanFactory(beanFactory) => 后置增強Bean(擴(kuò)展實現(xiàn))
空方法，方便擴(kuò)展
方法5：invokeBeanFactoryPostProcessors(beanFactory) => 執(zhí)行BFPP
實例化并且執(zhí)行BeanFactoryPostProcessors
?/**
??*?Instantiate?and?invoke?all?registered?BeanFactoryPostProcessor?beans,
??*?respecting?explicit?order?if?given.
??*?Must?be?called?before?singleton?instantiation.
??*?單例對象之前一定調(diào)用，因為單例bean創(chuàng)建后就只有一份
??*/
?protected?void?invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory?beanFactory)?{
??PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory,?getBeanFactoryPostProcessors());
??//?Detect?a?LoadTimeWeaver?and?prepare?for?weaving,?if?found?in?the?meantime
??//?(e.g.?through?an?@Bean?method?registered?by?ConfigurationClassPostProcessor)
??if?(beanFactory.getTempClassLoader()?==?null?&&?beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME))?{
???beanFactory.addBeanPostProcessor(new?LoadTimeWeaverAwareProcessor(beanFactory));
???beanFactory.setTempClassLoader(new?ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
??}
?}
方法6：registerBeanPostProcessors(beanFactory) => 注冊BPP
實例化并且注冊所有的BeanPostProcessor。實例化Bean之前的準(zhǔn)備工作
?/**
??*?Instantiate?and?register?all?BeanPostProcessor?beans,
??*?respecting?explicit?order?if?given.
??*?Must?be?called?before?any?instantiation?of?application?beans.
??*/
?protected?void?registerBeanPostProcessors(ConfigurableListableBeanFactory?beanFactory)?{
??PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory,?this);
?}
方法7：initMessageSource() => 國際化設(shè)置
方法8：initApplicationEventMulticaster() => 初始化應(yīng)用程序的多波器和廣播器
也屬于準(zhǔn)備工作
方法9：onRefresh() => 預(yù)留給子類做擴(kuò)展
空方法
方法10：registerListeners() => 注冊監(jiān)聽器
也屬于準(zhǔn)備工作
?/**
??*?Add?beans?that?implement?ApplicationListener?as?listeners.
??*?Doesn't?affect?other?listeners,?which?can?be?added?without?being?beans.
??*/
?protected?void?registerListeners()?{
??//?Register?statically?specified?listeners?first.
??for?(ApplicationListener?listener?:?getApplicationListeners())?{
???getApplicationEventMulticaster().addApplicationListener(listener);
??}
??//?Do?not?initialize?FactoryBeans?here:?We?need?to?leave?all?regular?beans
??//?uninitialized?to?let?post-processors?apply?to?them!
??String[]?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?earlyEventsToProcess?=?this.earlyApplicationEvents;
??this.earlyApplicationEvents?=?null;
??if?(earlyEventsToProcess?!=?null)?{
???for?(ApplicationEvent?earlyEvent?:?earlyEventsToProcess)?{
????getApplicationEventMulticaster().multicastEvent(earlyEvent);
???}
??}
?}
方法11：finishBeanFactoryInitialization(beanFactory) => 實例化所有單例對象
面試常問，工作常用。過程比較復(fù)雜
?/**
??*?Finish?the?initialization?of?this?context's?bean?factory,
??*?initializing?all?remaining?singleton?beans.
??*/
?protected?void?finishBeanFactoryInitialization(ConfigurableListableBeanFactory?beanFactory)?{
??//?Initialize?conversion?service?for?this?context.
??/**
???*?把類型轉(zhuǎn)化操作，設(shè)置到當(dāng)前的beanFactory里面去
??**/
??if?(beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME)?&&
????beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME,?ConversionService.class))?{
???beanFactory.setConversionService(
?????beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME,?ConversionService.class));
??}
??//?Register?a?default?embedded?value?resolver?if?no?bean?post-processor
??//?(such?as?a?PropertyPlaceholderConfigurer?bean)?registered?any?before:
??//?at?this?point,?primarily?for?resolution?in?annotation?attribute?values.
??/**
???*?判斷當(dāng)前的beanFactory有沒有內(nèi)置的值處理器
??**/
??if?(!beanFactory.hasEmbeddedValueResolver())?{
???beanFactory.addEmbeddedValueResolver(strVal?->?getEnvironment().resolvePlaceholders(strVal));
??}
??//?Initialize?LoadTimeWeaverAware?beans?early?to?allow?for?registering?their?transformers?early.
??/**
???*?織入Aware
??**/
??String[]?weaverAwareNames?=?beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class,?false,?false);
??for?(String?weaverAwareName?:?weaverAwareNames)?{
???getBean(weaverAwareName);
??}
??//?Stop?using?the?temporary?ClassLoader?for?type?matching.
??//?設(shè)置類加載器
??beanFactory.setTempClassLoader(null);
??//?Allow?for?caching?all?bean?definition?metadata,?not?expecting?further?changes.
??/**
???*?凍結(jié)：某些bean不需要進(jìn)行修改操作了，放入
??**/
??beanFactory.freezeConfiguration();
??//?Instantiate?all?remaining?(non-lazy-init)?singletons.
??/**
???*?實例化所有非懶加載的實例對象(重要)
??**/
??beanFactory.preInstantiateSingletons();
?}
實例化所有非懶加載的實例對象方法：
?@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.
??/**
???*?拿到所有注冊bean的名稱
???**/
??List?beanNames?=?new?ArrayList<>(this.beanDefinitionNames);
??//?Trigger?initialization?of?all?non-lazy?singleton?beans...
??//?循環(huán)去創(chuàng)建我們需要的單例對象
??for?(String?beanName?:?beanNames)?{
??????//?拿到bean的定義信息，就是我們在xml配置文件里面指定的一些屬性
???RootBeanDefinition?bd?=?getMergedLocalBeanDefinition(beanName);
???//?是否是抽象的，是否是單例的，是否是懶加載的
???if?(!bd.isAbstract()?&&?bd.isSingleton()?&&?!bd.isLazyInit())?{
???????//?判斷當(dāng)前類是否實現(xiàn)了factoryBean接口。一般沒實現(xiàn)，直接進(jìn)入下面的getBean
????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)
???????????((SmartFactoryBean)?factory)::isEagerInit,
?????????getAccessControlContext());
??????}
??????else?{
???????isEagerInit?=?(factory?instanceof?SmartFactoryBean?&&
?????????((SmartFactoryBean)?factory).isEagerInit());
??????}
??????if?(isEagerInit)?{
???????getBean(beanName);
??????}
?????}
????}
????else?{
????????//?通過beanName。拿到bean
?????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 重要方法：
getMergedLocalBeanDefinition
?/**
??*?Return?a?merged?RootBeanDefinition,?traversing?the?parent?bean?definition
??*?if?the?specified?bean?corresponds?to?a?child?bean?definition.
??*?@param?beanName?the?name?of?the?bean?to?retrieve?the?merged?definition?for
??*?@return?a?(potentially?merged)?RootBeanDefinition?for?the?given?bean
??*?@throws?NoSuchBeanDefinitionException?if?there?is?no?bean?with?the?given?name
??*?@throws?BeanDefinitionStoreException?in?case?of?an?invalid?bean?definition
??*/
??//?返回一個合并好的RootBeanDefinition。整合子類和父類
?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?&&?!mbd.stale)?{
???return?mbd;
??}
??return?getMergedBeanDefinition(beanName,?getBeanDefinition(beanName));
?}
getBean() => doGetBean()
?/**
??*?Return?an?instance,?which?may?be?shared?or?independent,?of?the?specified?bean.
??*?@param?name?the?name?of?the?bean?to?retrieve
??*?@param?requiredType?the?required?type?of?the?bean?to?retrieve
??*?@param?args?arguments?to?use?when?creating?a?bean?instance?using?explicit?arguments
??*?(only?applied?when?creating?a?new?instance?as?opposed?to?retrieving?an?existing?one)
??*?@param?typeCheckOnly?whether?the?instance?is?obtained?for?a?type?check,
??*?not?for?actual?use
??*?@return?an?instance?of?the?bean
??*?@throws?BeansException?if?the?bean?could?not?be?created
??*/
?@SuppressWarnings("unchecked")
?protected??T?doGetBean(final?String?name,?@Nullable?final?Class?requiredType,
???@Nullable?final?Object[]?args,?boolean?typeCheckOnly)?throws?BeansException?{
????????//?獲取beanName
??final?String?beanName?=?transformedBeanName(name);
??Object?bean;
??//?Eagerly?check?singleton?cache?for?manually?registered?singletons.
??//?單例檢查，如果一級，二級，三級緩存中存在該Bean,直接獲取到了
??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?+?"'");
????}
???}
???bean?=?getObjectForBeanInstance(sharedInstance,?name,?beanName,?null);
??}
??else?{
???//?Fail?if?we're?already?creating?this?bean?instance:
???//?We're?assumably?within?a?circular?reference.
???//?如果是單例對象的話，嘗試解決循環(huán)依賴問題
???if?(isPrototypeCurrentlyInCreation(beanName))?{
????throw?new?BeanCurrentlyInCreationException(beanName);
???}
???//?Check?if?bean?definition?exists?in?this?factory.
???//?獲取父類容器
???BeanFactory?parentBeanFactory?=?getParentBeanFactory();
???if?(parentBeanFactory?!=?null?&&?!containsBeanDefinition(beanName))?{
????//?Not?found?->?check?parent.
????String?nameToLookup?=?originalBeanName(name);
????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);
????}
???}
????????????//?標(biāo)志位。如果不是類型檢查，表示要創(chuàng)建bean,此處在集合中做一個記錄
???if?(!typeCheckOnly)?{
????markBeanAsCreated(beanName);
???}
???try?{
???????//?獲取beanDefinition
????final?RootBeanDefinition?mbd?=?getMergedLocalBeanDefinition(beanName);
????//?檢測beanDefinition
????checkMergedBeanDefinition(mbd,?beanName,?args);
????//?Guarantee?initialization?of?beans?that?the?current?bean?depends?on.
????//?檢查當(dāng)前的bean是否有其他依賴的bean
????String[]?dependsOn?=?mbd.getDependsOn();
????if?(dependsOn?!=?null)?{
????????//?如果有依賴的bean,我們要先遞歸解決其他依賴的bean
?????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);
??????try?{
???????getBean(dep);
??????}
??????catch?(NoSuchBeanDefinitionException?ex)?{
???????throw?new?BeanCreationException(mbd.getResourceDescription(),?beanName,
?????????"'"?+?beanName?+?"'?depends?on?missing?bean?'"?+?dep?+?"'",?ex);
??????}
?????}
????}
????//?Create?bean?instance.
????//?是否是單例的
????if?(mbd.isSingleton())?{
?????sharedInstance?=?getSingleton(beanName,?()?->?{
??????try?{
???????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;
?}
getSingleton
?/**
??*?Return?the?(raw)?singleton?object?registered?under?the?given?name,
??*?creating?and?registering?a?new?one?if?none?registered?yet.
??*?@param?beanName?the?name?of?the?bean
??*?@param?singletonFactory?the?ObjectFactory?to?lazily?create?the?singleton
??*?with,?if?necessary
??*?@return?the?registered?singleton?object
??*/
?public?Object?getSingleton(String?beanName,?ObjectFactory?singletonFactory)?{
??Assert.notNull(beanName,?"Bean?name?must?not?be?null");
??synchronized?(this.singletonObjects)?{
???Object?singletonObject?=?this.singletonObjects.get(beanName);
???if?(singletonObject?==?null)?{
????if?(this.singletonsCurrentlyInDestruction)?{
?????throw?new?BeanCreationNotAllowedException(beanName,
???????"Singleton?bean?creation?not?allowed?while?singletons?of?this?factory?are?in?destruction?"?+
???????"(Do?not?request?a?bean?from?a?BeanFactory?in?a?destroy?method?implementation!)");
????}
????if?(logger.isDebugEnabled())?{
?????logger.debug("Creating?shared?instance?of?singleton?bean?'"?+?beanName?+?"'");
????}
????beforeSingletonCreation(beanName);
????boolean?newSingleton?=?false;
????boolean?recordSuppressedExceptions?=?(this.suppressedExceptions?==?null);
????if?(recordSuppressedExceptions)?{
?????this.suppressedExceptions?=?new?LinkedHashSet<>();
????}
????try?{
????????//?實際上就是調(diào)用了CreateBean
?????singletonObject?=?singletonFactory.getObject();
?????newSingleton?=?true;
????}
????catch?(IllegalStateException?ex)?{
?????//?Has?the?singleton?object?implicitly?appeared?in?the?meantime?->
?????//?if?yes,?proceed?with?it?since?the?exception?indicates?that?state.
?????singletonObject?=?this.singletonObjects.get(beanName);
?????if?(singletonObject?==?null)?{
??????throw?ex;
?????}
????}
????catch?(BeanCreationException?ex)?{
?????if?(recordSuppressedExceptions)?{
??????for?(Exception?suppressedException?:?this.suppressedExceptions)?{
???????ex.addRelatedCause(suppressedException);
??????}
?????}
?????throw?ex;
????}
????finally?{
?????if?(recordSuppressedExceptions)?{
??????this.suppressedExceptions?=?null;
?????}
?????afterSingletonCreation(beanName);
????}
????if?(newSingleton)?{
?????addSingleton(beanName,?singletonObject);
????}
???}
???return?singletonObject;
??}
?}
doCreateBean => 通過上方法的singletonObject = singletonFactory.getObject();進(jìn)入的
?/**
??*?Actually?create?the?specified?bean.?Pre-creation?processing?has?already?happened
??*?at?this?point,?e.g.?checking?{@code?postProcessBeforeInstantiation}?callbacks.
??*?Differentiates?between?default?bean?instantiation,?use?of?a
??*?factory?method,?and?autowiring?a?constructor.
??*?@param?beanName?the?name?of?the?bean
??*?@param?mbd?the?merged?bean?definition?for?the?bean
??*?@param?args?explicit?arguments?to?use?for?constructor?or?factory?method?invocation
??*?@return?a?new?instance?of?the?bean
??*?@throws?BeanCreationException?if?the?bean?could?not?be?created
??*?@see?#instantiateBean
??*?@see?#instantiateUsingFactoryMethod
??*?@see?#autowireConstructor
??*/
?protected?Object?doCreateBean(final?String?beanName,?final?RootBeanDefinition?mbd,?final?@Nullable?Object[]?args)
???throws?BeanCreationException?{
??//?Instantiate?the?bean.
??BeanWrapper?instanceWrapper?=?null;
??if?(mbd.isSingleton())?{
???instanceWrapper?=?this.factoryBeanInstanceCache.remove(beanName);
??}
??if?(instanceWrapper?==?null)?{
??????/**
???????*?核心的創(chuàng)建實例化Bean的過程
??????**/
???instanceWrapper?=?createBeanInstance(beanName,?mbd,?args);
??}
??final?Object?bean?=?instanceWrapper.getWrappedInstance();
??Class?beanType?=?instanceWrapper.getWrappedClass();
??if?(beanType?!=?NullBean.class)?{
???mbd.resolvedTargetType?=?beanType;
??}
??//?Allow?post-processors?to?modify?the?merged?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.
??boolean?earlySingletonExposure?=?(mbd.isSingleton()?&&?this.allowCircularReferences?&&
????isSingletonCurrentlyInCreation(beanName));
????
??/**
???*?解決循環(huán)依賴。使用三級緩存
??**/
??if?(earlySingletonExposure)?{
???if?(logger.isTraceEnabled())?{
????logger.trace("Eagerly?caching?bean?'"?+?beanName?+
??????"'?to?allow?for?resolving?potential?circular?references");
???}
???addSingletonFactory(beanName,?()?->?getEarlyBeanReference(beanName,?mbd,?bean));
??}
??//?Initialize?the?bean?instance.
??Object?exposedObject?=?bean;
??try?{
??????/**
???????*?填充屬性，上文的實例化只是默認(rèn)屬性值。填充屬性是初始化的第一步，第二步是執(zhí)行init方法
??????**/
???populateBean(beanName,?mbd,?instanceWrapper);
???/**
????*?執(zhí)行init方法
???**/
???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?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?"?+
????????"'getBeanNamesOfType'?with?the?'allowEagerInit'?flag?turned?off,?for?example.");
?????}
????}
???}
??}
??//?Register?bean?as?disposable.
??try?{
??????/**
???????*?需要銷毀的時候，銷毀的鉤子函數(shù)
??????**/
???registerDisposableBeanIfNecessary(beanName,?bean,?mbd);
??}
??catch?(BeanDefinitionValidationException?ex)?{
???throw?new?BeanCreationException(
?????mbd.getResourceDescription(),?beanName,?"Invalid?destruction?signature",?ex);
??}
??return?exposedObject;
?}
面試題：為甚么循環(huán)依賴的解決要使用三級緩存？
createBeanInstance => 核心的創(chuàng)建和實例化bean的過程，由doCreateBean調(diào)用
大量的反射出現(xiàn)在該方法中，用來創(chuàng)建對象
?/**
??*?Create?a?new?instance?for?the?specified?bean,?using?an?appropriate?instantiation?strategy:
??*?factory?method,?constructor?autowiring,?or?simple?instantiation.
??*?@param?beanName?the?name?of?the?bean
??*?@param?mbd?the?bean?definition?for?the?bean
??*?@param?args?explicit?arguments?to?use?for?constructor?or?factory?method?invocation
??*?@return?a?BeanWrapper?for?the?new?instance
??*?@see?#obtainFromSupplier
??*?@see?#instantiateUsingFactoryMethod
??*?@see?#autowireConstructor
??*?@see?#instantiateBean
??*/
?protected?BeanWrapper?createBeanInstance(String?beanName,?RootBeanDefinition?mbd,?@Nullable?Object[]?args)?{
??//?Make?sure?bean?class?is?actually?resolved?at?this?point.
??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());
??}
??Supplier?instanceSupplier?=?mbd.getInstanceSupplier();
??if?(instanceSupplier?!=?null)?{
???return?obtainFromSupplier(instanceSupplier,?beanName);
??}
??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);
???}
??}
??//?Candidate?constructors?for?autowiring?
??//?構(gòu)造器
??Constructor[]?ctors?=?determineConstructorsFromBeanPostProcessors(beanClass,?beanName);
??if?(ctors?!=?null?||?mbd.getResolvedAutowireMode()?==?AUTOWIRE_CONSTRUCTOR?||
????mbd.hasConstructorArgumentValues()?||?!ObjectUtils.isEmpty(args))?{
???return?autowireConstructor(beanName,?mbd,?ctors,?args);
??}
??//?Preferred?constructors?for?default?construction?
??ctors?=?mbd.getPreferredConstructors();
??if?(ctors?!=?null)?{
???return?autowireConstructor(beanName,?mbd,?ctors,?null);
??}
??//?No?special?handling:?simply?use?no-arg?constructor.
??/**
???*?默認(rèn)無參構(gòu)造
???**/
??return?instantiateBean(beanName,?mbd);
?}
instantiateBean(beanName, mbd) => 默認(rèn)無參構(gòu)造
?/**
??*?Instantiate?the?given?bean?using?its?default?constructor.
??*?@param?beanName?the?name?of?the?bean
??*?@param?mbd?the?bean?definition?for?the?bean
??*?@return?a?BeanWrapper?for?the?new?instance
??*/
?protected?BeanWrapper?instantiateBean(final?String?beanName,?final?RootBeanDefinition?mbd)?{
??try?{
???Object?beanInstance;
???final?BeanFactory?parent?=?this;
???if?(System.getSecurityManager()?!=?null)?{
????beanInstance?=?AccessController.doPrivileged((PrivilegedActioninstantiate
?@Override
?public?Object?instantiate(RootBeanDefinition?bd,?@Nullable?String?beanName,?BeanFactory?owner)?{
??//?Don't?override?the?class?with?CGLIB?if?no?overrides.
??if?(!bd.hasMethodOverrides())?{
???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(
?????????(PrivilegedExceptionAction>)?clazz::getDeclaredConstructor);
??????}
??????else?{
???????constructorToUse?=?clazz.getDeclaredConstructor();
??????}
??????bd.resolvedConstructorOrFactoryMethod?=?constructorToUse;
?????}
?????catch?(Throwable?ex)?{
??????throw?new?BeanInstantiationException(clazz,?"No?default?constructor?found",?ex);
?????}
????}
???}
???return?BeanUtils.instantiateClass(constructorToUse);
??}
??else?{
???//?Must?generate?CGLIB?subclass.
???return?instantiateWithMethodInjection(bd,?beanName,?owner);
??}
?}
BeanUtils.instantiateClass => 通過構(gòu)造器反射創(chuàng)建bean
?/**
??*?Convenience?method?to?instantiate?a?class?using?the?given?constructor.
??*?Note?that?this?method?tries?to?set?the?constructor?accessible?if?given?a
??*?non-accessible?(that?is,?non-public)?constructor,?and?supports?Kotlin?classes
??*?with?optional?parameters?and?default?values.
??*?@param?ctor?the?constructor?to?instantiate
??*?@param?args?the?constructor?arguments?to?apply?(use?{@code?null}?for?an?unspecified
??*?parameter,?Kotlin?optional?parameters?and?Java?primitive?types?are?supported)
??*?@return?the?new?instance
??*?@throws?BeanInstantiationException?if?the?bean?cannot?be?instantiated
??*?@see?Constructor#newInstance
??*/
?public?static??T?instantiateClass(Constructor?ctor,?Object...?args)?throws?BeanInstantiationException?{
??Assert.notNull(ctor,?"Constructor?must?not?be?null");
??try?{
???ReflectionUtils.makeAccessible(ctor);
???if?(KotlinDetector.isKotlinReflectPresent()?&&?KotlinDetector.isKotlinType(ctor.getDeclaringClass()))?{
????return?KotlinDelegate.instantiateClass(ctor,?args);
???}
???else?{
????Class[]?parameterTypes?=?ctor.getParameterTypes();
????Assert.isTrue(args.length?<=?parameterTypes.length,?"Can't?specify?more?arguments?than?constructor?parameters");
????Object[]?argsWithDefaultValues?=?new?Object[args.length];
????for?(int?i?=?0?;?i??????if?(args[i]?==?null)?{
??????Class?parameterType?=?parameterTypes[i];
??????argsWithDefaultValues[i]?=?(parameterType.isPrimitive()???DEFAULT_TYPE_VALUES.get(parameterType)?:?null);
?????}
?????else?{
??????argsWithDefaultValues[i]?=?args[i];
?????}
????}
????return?ctor.newInstance(argsWithDefaultValues);
???}
??}
??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());
??}
?}
方法12：finishRefresh() => 完成刷新
?/**
??*?Finish?the?refresh?of?this?context,?invoking?the?LifecycleProcessor's
??*?onRefresh()?method?and?publishing?the
??*?{@link?org.springframework.context.event.ContextRefreshedEvent}.
??*/
?protected?void?finishRefresh()?{
??//?Clear?context-level?resource?caches?(such?as?ASM?metadata?from?scanning).
??//?
??clearResourceCaches();
??//?Initialize?lifecycle?processor?for?this?context.
??initLifecycleProcessor();
??//?Propagate?refresh?to?lifecycle?processor?first.
??getLifecycleProcessor().onRefresh();
??//?Publish?the?final?event.
??publishEvent(new?ContextRefreshedEvent(this));
??//?Participate?in?LiveBeansView?MBean,?if?active.
??LiveBeansView.registerApplicationContext(this);
?}
方法13：resetCommonCaches() => 緩存重置
?/**
??*?Reset?Spring's?common?reflection?metadata?caches,?in?particular?the
??*?{@link?ReflectionUtils},?{@link?AnnotationUtils},?{@link?ResolvableType}
??*?and?{@link?CachedIntrospectionResults}?caches.
??*?@since?4.2
??*?@see?ReflectionUtils#clearCache()
??*?@see?AnnotationUtils#clearCache()
??*?@see?ResolvableType#clearCache()
??*?@see?CachedIntrospectionResults#clearClassLoader(ClassLoader)
??*/
?protected?void?resetCommonCaches()?{
??ReflectionUtils.clearCache();
??AnnotationUtils.clearCache();
??ResolvableType.clearCache();
??CachedIntrospectionResults.clearClassLoader(getClassLoader());
?}
最后回顧整個流程概覽圖：
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