Spring Ioc 容器 创建Bean 的流程
1、Spring 版本 3.1
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2、BeanFactory 创建bean 流程:
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以 DefaultListableBeanFactory 为例说明BeanFactory 创建bean的流程。 DefaultListableBeanFactory是Spring提供的两个重要的BeanFactory的实现
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2.1、当我们调用类似 DefaultListableBeanFactory 的getBean(...) 方法时候、 会去调用其父类AbstractAutowireCapableBeanFactory 的 createBean(...) 方法：
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2.2、 AbstractAutowireCapableBeanFactory 的 createBean 如下：
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protected Object createBean( final String beanName, final RootBeanDefinition mbd,
??????? final Object[] args) throws BeanCreationException {
???? .... // 省略
????? // Make sure bean class is actually resolved at this point.
????? resolveBeanClass(mbd, beanName); // ????? // Prepare method overrides.
???? try {
??????? mbd.prepareMethodOverrides(); // 2.2.2 ???
???? }catch (BeanDefinitionValidationException ex) {
?????? .... // 省略
???? }
???? try {
?? // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
??? // 2.2.3.???? Object bean = resolveBeforeInstantiation(beanName, mbd);
???? if (bean != null ) {
????? return bean; // 2.2.4.???? }
??? }catch (Throwable ex) {
???? ... // 省略
?????? }
??? Object beanInstance = doCreateBean(beanName, mbd, args);//2.2.5. ????? ... // 省略
??? return beanInstance;
??? //2.3.1、构造Bean，并返回bean 的 BeanWrapper 类
? BeanWrapper instanceWrapper = null ;
? if (mbd.isSingleton()) {
????? instanceWrapper = this .factoryBeanInstanceCache .remove(beanName);
? }
? if (instanceWrapper == null ) {
????? instanceWrapper = createBeanInstance(beanName, mbd, args);
? }
? final Object bean = (instanceWrapper != null ?instanceWrapper .getWrappedInstance(): null);
? Class beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null );
? // Allow post-processors to modify the merged bean definition.
?? //2.3.2、回调MergedBeanDefinitionPostProcessor的postProcessMergedBeanDefinition接口
? synchronized (mbd. postProcessingLock ) {
????? if (!mbd. postProcessed ) {
????????? applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
????????? 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));
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? if (earlySingletonExposure) {
????? // ... 省略日志
????? addSingletonFactory(beanName, new ObjectFactory() {
????????? public Object getObject() throws BeansException {
????????????????? ????????????? return getEarlyBeanReference(beanName, mbd, bean);
????????? }
????? });
? }
? // Initialize the bean instance.
? Object exposedObject = bean;
? try {
??????? ??? populateBean(beanName, mbd, instanceWrapper);
??? if (exposedObject != null ) {
??????? ??????? exposedObject = initializeBean(beanName, exposedObject, mbd);
??? }
?? } catch (Throwable ex) {
????? // ... 省略
? }
? if (earlySingletonExposure) {
????? // ... 省略部分代码, 代码用途???
? }
? // Register bean as disposable.
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?? // 注册Bean的销毁回调
? try {
????? registerDisposableBeanIfNecessary(beanName, bean, mbd);
? } catch (BeanDefinitionValidationException ex) {
????? // ... 省略
? }
? return exposedObject;
protected voidpopulateBean(String beanName, AbstractBeanDefinition mbd,
?????????????? BeanWrapper bw) {
???? PropertyValuespvs = mbd.getPropertyValues();
???? if (bw == null) {
??????? if (!pvs.isEmpty()) {
??????????? // ... 省略
??????? }else {
???????? // Skip property population phase for null instance.
???????? return;
???? ? ?}
???? }
???? // Give any InstantiationAwareBeanPostProcessors theopportunity to modify the
???? // state of the bean before properties are set. This canbe used, for example,
???? // to support styles of field injection.
???? booleancontinueWithPropertyPopulation = true;
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???? if (!mbd.isSynthetic()&& hasInstantiationAwareBeanPostProcessors()) {
???????? for (BeanPostProcessor bp :getBeanPostProcessors()) {
???????????? if (bp instanceofInstantiationAwareBeanPostProcessor) {
???????????????? InstantiationAwareBeanPostProcessoribp =
????????????????????????????????????? (InstantiationAwareBeanPostProcessor) bp;
???????????????? if(!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
???????????????? ? ? continueWithPropertyPopulation= false;
???????????????????? break;
????????????????? }
???? ? ? ? ??}
????????? }
???? }
??? if(!continueWithPropertyPopulation) {
?????? return;
??? }
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?????? ??? if(mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME||
???????? mbd.getResolvedAutowireMode()== RootBeanDefinition.AUTOWIRE_BY_TYPE) {
??????? MutablePropertyValuesnewPvs = newMutablePropertyValues(pvs);
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?????? // Add property values based on autowire by name ifapplicable.
?????? if(mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME){
?????????? autowireByName(beanName,mbd, bw, newPvs);
?????? }
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?????? // Add property values based on autowire by type ifapplicable.
?????? if(mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE){
??????????? autowireByType(beanName,mbd, bw, newPvs);
?????? }
?????? pvs= newPvs;
??? }
??? boolean hasInstAwareBpps =hasInstantiationAwareBeanPostProcessors();
?????? boolean needsDepCheck =(mbd.getDependencyCheck()??
??????????????????????????????????????? !=RootBeanDefinition.DEPENDENCY_CHECK_NONE);
???????
??? if (hasInstAwareBpps ||needsDepCheck) {
??????? PropertyDescriptor[]filteredPds = filterPropertyDescriptorsForDependencyCheck(bw);
????????????? ??????? if (hasInstAwareBpps) {
????????????????? for (BeanPostProcessor bp :getBeanPostProcessors()) {
????????????? if (bp instanceofInstantiationAwareBeanPostProcessor) {
????????????????? InstantiationAwareBeanPostProcessoribp =
??????????????????????????????????????????????? (InstantiationAwareBeanPostProcessor) bp;
????????????????? pvs= ibp.postProcessPropertyValues(pvs, filteredPds,
?????????????????????????????????? bw.getWrappedInstance(), beanName);
????????????????? if (pvs == null) {
????????????????????? return;
????????????????? }?
????????????? }
????????? }
?????? }
???????????? ?????? if (needsDepCheck) {
?????????? checkDependencies(beanName,mbd, filteredPds, pvs);
?????? }
??????????? ??????????? applyPropertyValues(beanName, mbd, bw, pvs);
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}
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注意： 2.4.2、 执行其它的依赖注入， 当Spring 配置文件中有<context:annotation-config/> 这样的标签，并且
????????????????????? 使用Spring 的ApplicationContext 容器(BeanFactory 不会自动注册) 会自动注册一些内置的
????????????????????? BeanPostProcessors, 这些BeanPostProcessesors 将会在此处用到，完成一些注入工作。
???????? ? ? ? ? ? ? a、AutowiredAnnotationBeanPostProcessor? 执行@Autowired注入
???????? ? ? ? ? ? ? b、CommonAnnotationBeanPostProcessor?? 执行@Resource 注入
???????????????????? c、 RequiredAnnotationBeanPostProcessor? 执行@Required 的注入检查
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public void refresh() throws BeansException,IllegalStateException {
??????? synchronized (this.startupShutdownMonitor){
??????????? // Prepare this context for refreshing.
??????????? prepareRefresh();
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??????????? // Tell the subclass to refresh the internal beanfactory.
??????????? ConfigurableListableBeanFactorybeanFactory = obtainFreshBeanFactory();
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??????????? // Prepare the bean factory for use in this context.
???????????????????? // 3.2.1为BeanFactory 注册一些内部 BeanPostProcess 如
???????????????????? //? (ApplicationContextAwareProcessor)
??????????? prepareBeanFactory(beanFactory);
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??????????? try {
??????????????? // Allows post-processing of the bean factory in contextsubclasses.
??????????????? postProcessBeanFactory(beanFactory);
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??????????????? // Invoke factory processors registered as beans in thecontext.
?????????????? // 3.2.2 调用在配置文件中定义的 BeanFactoryPostProcessor bean 方法的 ?????????????? // postProcessBeanFactory(...) 方法
????????????????????????? invokeBeanFactoryPostProcessors(beanFactory);
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??????????????? // Register bean processors that intercept bean creation.
?????????????????????????? // 3.2.3 注册内部的BeanPostProcessors 如有<context:annotation-config/>
?????????????????????????? // 这个标签将注册如下 BeanPostProcessors:
????????????????????????? //AutowiredAnnotationBeanPostProcessor,CommonAnnotationBeanPostProcessor
????????????????????????? //RequiredAnnotationBeanPostProcessor 等.
?????????????? registerBeanPostProcessors(beanFactory);
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??????????????? // Initialize message source for this context.
??????????????????????????? // 3.2.4 初始化ApplicationContext 内部的 MessageSource
??????????????? initMessageSource();
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??????????????? // Initialize event multicaster for this context.
????????????????????????????// 3.2.5 初始化ApplicationContext 内部的 applicationEventMulticaster
??????????????? initApplicationEventMulticaster();
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??????????????? // Initialize other special beans in specific contextsubclasses.
??????????????? onRefresh();
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??????????????? // Check for listener beans and register them.
??????????????????????????? // 3.2.6 注册 ApplicationListeners 在配置文件cotext 中查找ApplcationListeners
?????????????????????????? // 并注册他们。
??????????????? registerListeners();
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??????????????? // Instantiate all remaining (non-lazy-init) singletons.
??????????????????????????? // 3.2.7 初始化配置文件 context 中的所有的singleton 并且lazy-init="false"的bean
??????????????????????????? // 如果scope 不是singleton, bean将不会初始化
??????????????? finishBeanFactoryInitialization(beanFactory);
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??????????????? // Last step: publish corresponding event.
??????????????????????????? // 3.2.8 初始化 lifecycle processor，调用LifecycleProcessor 的onRefresh() 方法
??????????????????????????? // publish ContextRefreshedEvent;
??????????????? finishRefresh();
??????????? }
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??????????? catch (BeansException ex) {
??????????????? // Destroy already created singletons to avoid danglingresources.
??????????????? destroyBeans();
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??????????????? // Reset 'active' flag.
??????????????? cancelRefresh(ex);
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??????????????? // Propagate exception to caller.
??????????????? throw ex;
??????? ??? }
??????? }
??? }
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3.3 然后接下来流程将调用BeanFactory 创建Bean 的方法.
