spring学习之源码分析--AbstractApplicationContext之refresh

spring学习之源码分析--AnnotationConfigApplicationContext之register和scan 中，讲了注解形式是怎么注册BeanDefinition的，注册完后，有了bean的定义信息，当然是初始化容器了。

refresh

public void refresh() throws BeansException, IllegalStateException {

    synchronized (this.startupShutdownMonitor) {
        // Prepare this context for refreshing.
        // 准备刷新的上下文环境
        prepareRefresh();

        // Tell the subclass to refresh the internal bean factory.
        // 获取beanFactory
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

        // Prepare the bean factory for use in this context.

        // 设置beanFactory的各个属性
        prepareBeanFactory(beanFactory);

        try {
            // Allows post-processing of the bean factory in context subclasses.
            // 模板模式，留给子类通过重写这个方法来做其他处理
            postProcessBeanFactory(beanFactory);

            // Invoke factory processors registered as beans in the context.
            // BeanFactoryPostProcessorc，BeanFactory的后置处理器处理
            invokeBeanFactoryPostProcessors(beanFactory);

            // Register bean processors that intercept bean creation.
            // 注册BeanPostProcessors，拦截bean的创建过程，bean在这个时候还没创建
            registerBeanPostProcessors(beanFactory);

            // Initialize message source for this context.
            // 国际化处理
            initMessageSource();

            // Initialize event multicaster for this context.
            // 初始化事件派发器
            initApplicationEventMulticaster();

            // Initialize other special beans in specific context subclasses.
            // 模板模式，留给子类通过重写这个方法来做其他处理
            onRefresh();

            // Check for listener beans and register them.
            // 注册ApplicationListener到applicationEventMulticaster
            registerListeners();

            // Instantiate all remaining (non-lazy-init) singletons.
            // 初始化所有的单例，除了延迟加载的bean
            finishBeanFactoryInitialization(beanFactory);

            // Last step: publish corresponding event.
            // 通知别人说已经完成了
            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();
        }
    }
}

prepareRefresh

刷新前的准备，对容器属性的初始化，校验属性文件的合法性，保留早期事件

protected void prepareRefresh() {
    // Switch to active.
    // 启动时间
    this.startupDate = System.currentTimeMillis();
    // 容器是否关闭
    this.closed.set(false);
    // 容器是否是活动状态
    this.active.set(true);

    if (logger.isDebugEnabled()) {
        if (logger.isTraceEnabled()) {
            logger.trace("Refreshing " + this);
        }
        else {
            logger.debug("Refreshing " + getDisplayName());
        }
    }

    // Initialize any placeholder property sources in the context environment.
    // 初始化属性，留给子类
    initPropertySources();

    // Validate that all properties marked as required are resolvable:
    // see ConfigurablePropertyResolver#setRequiredProperties
    // 校验属性文件是否合法
    getEnvironment().validateRequiredProperties();

    // Store pre-refresh ApplicationListeners...
    // 保留早期事件
    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...
    this.earlyApplicationEvents = new LinkedHashSet<>();
}

obtainFreshBeanFactory

获取beanFactory

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    refreshBeanFactory();
    return getBeanFactory();
}

// GenericApplicationContext.class
protected final void refreshBeanFactory() throws IllegalStateException {
    // refreshed为false才可以，只能一个线程执行refresh方法
    if (!this.refreshed.compareAndSet(false, true)) {
        throw new IllegalStateException(
                "GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
    }
    // 设置序列号，由于我们这个是通过AnnotationConfigApplicationContext查看的
    // 所以已经由AnnotationConfigApplicationContext的父类GenericApplicationContext初始化了beanFactory
    this.beanFactory.setSerializationId(getId());
}

prepareBeanFactory

设置beanFactory的各个属性

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    // Tell the internal bean factory to use the context's class loader etc.
    // 设置类加载器
    beanFactory.setBeanClassLoader(getClassLoader());
    // 设置表达式解析器
    beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    // 添加属性编辑器
    beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

    // Configure the bean factory with context callbacks.
    // 添加ApplicationContextAwareProcessor，根据不同的类型加入不同的属性
    beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    // 忽略一下几个接口的自动装配
    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.
    // 注册几个依赖类型和自动注入值
    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.
    // 注册ApplicationListenerDetector，如果bean是ApplicationListener的，加入到事件派发器
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

    // Detect a LoadTimeWeaver and prepare for weaving, if found.
    // 增加对AspectJ的支持
    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.
    // 注册默认的环境bean
    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());
    }
}

invokeBeanFactoryPostProcessors

我们先了解一下BeanFactoryPostProcessor接口，他有个方法，传递的参数是ConfigurableListableBeanFactory，也就是说，在refresh中，beanFactory初始化完成后，把这个beanFactory传给BeanFactoryPostProcessor。BeanFactoryPostProcessor可以在实例化bean前，自定义他的任何行为。与之类似的BeanPostProcessor，是bean级别的，BeanFactoryPostProcessor是容器级别的。两个针对不同的范围进行加强。

大概流程是：

1、先处理BeanDefinitionRegistryPostProcessor类型的

2、再处理其他类型的BeanFactoryPostProcessor

两种BeanFactoryPostProcessor都是按照PriorityOrdered>Ordered>其他的顺序执行。

通过AnnotationConfigApplicationContext扫描或注册后，bean里面的注解要怎么注入到容器呢，就是通过ConfigurationClassPostProcessor实现的，这个ConfigurationClassPostProcessor就是实现了BeanDefinitionRegistryPostProcessor和PriorityOrdered的接口。

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()));
    }
}

public static void invokeBeanFactoryPostProcessors(
        ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

    // Invoke BeanDefinitionRegistryPostProcessors first, if any.
    // 保存被处理过的beanName
    Set<String> processedBeans = new HashSet<>();
    // 如果是BeanDefinitionRegistry
    if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
        List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
        // BeanDefinitionRegistryPostProcessor先处理，保存在registryProcessors
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryProcessor =
                        (BeanDefinitionRegistryPostProcessor) postProcessor;
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            }
            else {
                // 保存常规的，非BeanDefinitionRegistryPostProcessor
                regularPostProcessors.add(postProcessor);
            }
        }

        // Do not initialize FactoryBeans here: We need to leave all regular beans
        // uninitialized to let the bean factory post-processors apply to them!
        // Separate between BeanDefinitionRegistryPostProcessors that implement
        // PriorityOrdered, Ordered, and the rest.
        List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

        // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
        // 获取BeanDefinitionRegistryPostProcessor类型的beanName
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            // 先执行实现了PriorityOrdered接口的bean
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                // 生成的bean保存在currentRegistryProcessors
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                // 保存被处理过的beanName
                processedBeans.add(ppName);
            }
        }
        // 对currentRegistryProcessors进行排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        // 全部添加到registryProcessors，此时所有的BeanFactoryPostProcessor，包括定义的bean，都保存在registryProcessors
        registryProcessors.addAll(currentRegistryProcessors);
        // 获取PriorityOrdered接口的BeanFactoryPostProcessor完后，进行后置处理
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        // 清空currentRegistryProcessors作其他用途
        currentRegistryProcessors.clear();

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        // 获取BeanDefinitionRegistryPostProcessor，且实现Ordered接口的。实现了PriorityOrdered接口的，通过processedBeans排除了
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                // 生成的bean保存在currentRegistryProcessors
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                // 保存被处理过的beanName
                processedBeans.add(ppName);
            }
        }
        // 对currentRegistryProcessors进行排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        // 全部添加到registryProcessors
        registryProcessors.addAll(currentRegistryProcessors);
        // 获取Ordered接口的BeanFactoryPostProcessor完后，进行后置处理
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        // 清空currentRegistryProcessors作其他用途
        currentRegistryProcessors.clear();

        // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
        // 为false说明已经遍历完了
        boolean reiterate = true;
        while (reiterate) {
            reiterate = false;
            // 获取processedBeans排除的BeanDefinitionRegistryPostProcessor
            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);
                    // 说明还有，继续遍历
                    reiterate = true;
                }
            }
            // 对currentRegistryProcessors进行排序
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            // 全部添加到registryProcessors
            registryProcessors.addAll(currentRegistryProcessors);
            // 获取的BeanFactoryPostProcessor完后，进行后置处理
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 清空currentRegistryProcessors作其他用途
            currentRegistryProcessors.clear();
        }

        // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
        // BeanDefinitionRegistryPostProcessor处理完了，再调用BeanFactoryPostProcessor的后置处理器。
        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
    }

    else {
        // Invoke factory processors registered with the context instance.
        // 直接调用BeanFactoryPostProcessor的后置处理器。
        invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
    }

    // Do not initialize FactoryBeans here: We need to leave all regular beans
    // uninitialized to let the bean factory post-processors apply to them!
    // 上面主要对BeanDefinitionRegistryPostProcessor和传入的参数beanFactoryPostProcessors两种后置处理器的调用
    // 下面是bean定义中BeanFactoryPostProcessor后置处理器的调用
    // 获取bean定义中BeanFactoryPostProcessor
    String[] postProcessorNames =
            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    List<String> orderedPostProcessorNames = new ArrayList<>();
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        // 已处理过的跳过
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
        }
        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            // 实现了PriorityOrdered接口的
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            // 实现了Ordered接口的
            orderedPostProcessorNames.add(ppName);
        }
        else {
            // 其他的
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
    // 先对实现了PriorityOrdered接口的排序，然后再调用后置处理器
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    // 先对实现了Ordered接口的排序，然后再调用后置处理器
    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.
    // 最后调用剩下的后置处理器
    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...
    // 因为后处理器可能有修改了原始的元数据，所以要清除缓存的合并bean定义
    beanFactory.clearMetadataCache();
}

registerBeanPostProcessors

注册BeanPostProcessor，这边并没有调用，只是注册，传递的参数是实例及beanName。真正的调用是在bean的实例化的时候。

整体流程跟上面BeanFactoryPostProcessor差不多，只是多了一个MergedBeanDefinitionPostProcessor。

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
    PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}

public static void registerBeanPostProcessors(
        ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
    // 获取所有的BeanPostProcessor
    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

    // Register BeanPostProcessorChecker that logs an info message when
    // a bean is created during BeanPostProcessor instantiation, i.e. when
    // a bean is not eligible for getting processed by all BeanPostProcessors.
    // 获取后置处理器的个数，这个+1就是加BeanPostProcessorChecker
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // Separate between BeanPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    // 下面这段代码是不是很熟悉，跟BeanFactoryPostProcessor一样的思想，先PriorityOrdered再Ordered最后其他
    List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
    List<String> orderedPostProcessorNames = new ArrayList<>();
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
            // 保存实现了PriorityOrdered接口的BeanPostProcessor
            priorityOrderedPostProcessors.add(pp);
            if (pp instanceof MergedBeanDefinitionPostProcessor) {
                // 保存实现了PriorityOrdered及MergedBeanDefinitionPostProcessor接口的BeanPostProcessor
                internalPostProcessors.add(pp);
            }
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            // 保存实现了Ordered接口的BeanPostProcessor
            orderedPostProcessorNames.add(ppName);
        }
        else {
            // 保存其他接口的BeanPostProcessor
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, register the BeanPostProcessors that implement PriorityOrdered.
    // PriorityOrdered接口，排序，注册到beanFactory
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    // Ordered接口，排序，注册到beanFactory，另外过滤MergedBeanDefinitionPostProcessor类型的加入到internalPostProcessors
    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);

    // Now, register all regular BeanPostProcessors.
    // 其他接口，注册到beanFactory，另外过滤MergedBeanDefinitionPostProcessor类型的加入到internalPostProcessors
    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.
    // MergedBeanDefinitionPostProcessor接口，排序，注册到beanFactory
    sortPostProcessors(internalPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, internalPostProcessors);

    // Re-register post-processor for detecting inner beans as ApplicationListeners,
    // moving it to the end of the processor chain (for picking up proxies etc).
    // 添加ApplicationListenerDetector监听
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

initMessageSource

国际化处理

protected void initMessageSource() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    // 如果beanFactory存在messageSource，赋值给messageSource
    if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
        this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
        // Make MessageSource aware of parent MessageSource.
        if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
            HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
            if (hms.getParentMessageSource() == null) {
                // Only set parent context as parent MessageSource if no parent MessageSource
                // registered already.
                hms.setParentMessageSource(getInternalParentMessageSource());
            }
        }
        if (logger.isTraceEnabled()) {
            logger.trace("Using MessageSource [" + this.messageSource + "]");
        }
    }
    else {
        // Use empty MessageSource to be able to accept getMessage calls.
        // beanFactory不存在messageSource，使用默认的
        DelegatingMessageSource dms = new DelegatingMessageSource();
        dms.setParentMessageSource(getInternalParentMessageSource());
        this.messageSource = dms;
        beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
        if (logger.isTraceEnabled()) {
            logger.trace("No '" + MESSAGE_SOURCE_BEAN_NAME + "' bean, using [" + this.messageSource + "]");
        }
    }
}

initApplicationEventMulticaster

初始化事件派发器

protected void initApplicationEventMulticaster() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    // 如果beanFactory存在applicationEventMulticaster，赋值给applicationEventMulticaster
    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 {
        // beanFactory不存在applicationEventMulticaster，使用默认的
        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() + "]");
        }
    }
}

registerListeners

注册监听

protected void registerListeners() {
    // Register statically specified listeners first.
    // 注入到事件派发器
    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!
    // 从配置信息获取监听注入到事件派发器
    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...
    // 早起的监听注册到事件派发器
    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
    this.earlyApplicationEvents = null;
    if (earlyEventsToProcess != null) {
        for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
            getApplicationEventMulticaster().multicastEvent(earlyEvent);
        }
    }
}

finishBeanFactoryInitialization

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
    // Initialize conversion service for this context.
    // 如果beanFactory存在conversionService，赋值给ConversionService
    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.
    if (!beanFactory.hasEmbeddedValueResolver()) {
        beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
    }

    // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
    String[] weaverAwareNames = beanFactoryFactoryBean.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
    for (String weaverAwareName : weaverAwareNames) {
        getBean(weaverAwareName);
    }

    // Stop using the temporary ClassLoader for type matching.
    // 此时不能用临时加载器了
    beanFactory.setTempClassLoader(null);

    // Allow for caching all bean definition metadata, not expecting further changes.
    // 冻结所有bean的定义，此时不希望bean的定义被修改
    beanFactory.freezeConfiguration();

    // Instantiate all remaining (non-lazy-init) singletons.
    // 初始化剩下的单例，且除了延迟加载的bean
    beanFactory.preInstantiateSingletons();
}

beanFactory.preInstantiateSingletons() 中，区分了普通bean和FactoryBean的实例化，如果是FactoryBean，则beanName加上&再实例化。

实例化调用的是getBean方法，实际调用的是doGetBean方法。doGetBean大概步骤如下：

1、transformedBeanName，获取beanName，有可能传过来的是原始的beanName，有可能是加了&的，有可能是别名。如果是加了&的，先去除，再获取。如果是别名，先递归到最原始的别名，再获取beanName。

2、getSingleton，获取到beanName后，通过beanName看单例缓存是否创建过了，有的话直接返回。如果singletonObjects和earlySingletonObjects两个缓存都没有，从singletonFactories加载。

3、 getObjectForBeanInstance ，得到的bean，是原始的bean，可能是普通的bean，也可能是FactoryBean，所以要通过这个方法处理一下，得到我们想要的bean。我们经常提及的后置处理器就是在这里调用的。

4、 isPrototypeCurrentlyInCreation ，如果没得到bean，就去创建一个bean，此时先判断是否是多例。在单例的时候，可能尝试解决循环依赖，如果是多例，会循环引用，是不允许的。

5、如果有父容器，当前容器没有这个bean的定义，说明了这个bean就有可能在父容器中，或者让父容器创建，一直递归上去。

6、 getMergedBeanDefinition ，父容器也没有，就只能根据bean的定义中创建了。原先的bean的定义，都是GenericBeanDefinition类型的，要转换为RootBeanDefinition类型。大体逻辑是这样的，如果mergedBeanDefinitions缓存有，直接返回，如果没有，看看有没有父类，有父类，递归上去找，并合并父类的属性。如果没有父类，判断是不是RootBeanDefinition类型的，如果是，直接复制，如果不是，就转换为RootBeanDefinition。

7、实例化之前，要先实例化依赖的对象。要判断是否循环依赖isDependent，再保存依赖的关系 registerDependentBean 。

8、如果是单例，getSingleton中先对缓存、创建状态进行处理，再通过回调createBean创建bean，最后调用getObjectForBeanInstance处理一下。（见3步骤）

9、如果是多例，调用createBean前后，要调用 beforePrototypeCreation 和 afterPrototypeCreation 来保存是否在创建的状态，防止循环引用，（见4步骤的判断）。创建bean后，再调用getObjectForBeanInstance处理一下。（见3步骤）

10、其他scope类型的判断，大概步骤同9.

11、根据类型转换需要的类型。