spring高级容器ApplicationContext之ref

我们在上节spring高级容器之ApplicationContext文章中对applicationContext容器的功能简单的了解下,我们还遗留了一个问题就是#refresh()方法的作用,可以说该方法为applicationContext容器的核心方法,也是我们值得学习的一个方法,接下来让我们来一起学习该方法,代码如下:

/**
 * 加载或者刷新配置方法(重要)
 * @throws BeansException
 * @throws IllegalStateException
 */
void refresh() throws BeansException, IllegalStateException;

上述是该方法的定义,在ConfigurableApplicationContext类中,我们其实根据方法名就能简答的猜出该方法的用处,就是用来刷新当前spring所处的上下文,我们接着看该方法的具体的实现过程,代码如下:

  public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        //准备刷新上下文
        prepareRefresh();

        //创建并初始化beanFactory
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

        //装配beanFactory
        prepareBeanFactory(beanFactory);

        try {
            //在当前上下文环境下对beanFactory进行后置处理操作
            postProcessBeanFactory(beanFactory);

            //激活各种BeanFactory的处理器
            invokeBeanFactoryPostProcessors(beanFactory);

            //注册拦截Bean创建的Bean处理器,即注册BeanPostProcessor
            registerBeanPostProcessors(beanFactory);

            //为上下文环境初始化MessageSource,即不同语言的消息体,国际化处理操作
            initMessageSource();

            //初始化上下文事件广播器
            initApplicationEventMulticaster();

            //此处是留给子类来初始化其他的bean
            onRefresh();

            //在所有bean中查找listener bean,然后注册到广播器中
            registerListeners();

            //初始化剩下的单例Bean(非延迟加载的)
            finishBeanFactoryInitialization(beanFactory);

            //完成刷新过程,通知生命周期处理器lifecycleProcessor刷新过程,同时发出ContextRefreshEvent通知别人
            finishRefresh();
        }

        catch (BeansException ex) {
            if (logger.isWarnEnabled()) {
                logger.warn("Exception encountered during context initialization - " +
                        "cancelling refresh attempt: " + ex);
            }

            //销毁已经创建的单例bean
            destroyBeans();

            // Reset 'active' flag.
            cancelRefresh(ex);

            // 抛异常
            throw ex;
        }

        finally {
            // Reset common introspection caches in Spring's core, since we
            // might not ever need metadata for singleton beans anymore...
            resetCommonCaches();
        }
    }
}

接下来我们分别来看看上述代码中的方法,注意:很重要

prepareRefresh()

该方法其主要的作用是对上下文环境的初始化准备工作,如对系统环境或者系统属性变量的准备验证过程,这个变量的设置可能会影响着系统的正确性,我们可以通过重写initPropertySources方法就可以了,代码如下:

/**
 * Prepare this context for refreshing, setting its startup date and
 * active flag as well as performing any initialization of property sources.
 */
protected void prepareRefresh() {
    // Switch to active.
    //设置启动时间
    this.startupDate = System.currentTimeMillis();
    //设置当前上下文(Context)的状态
    this.closed.set(false);
    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context environment（上下文环境）中的占位符属性来源
    initPropertySources();

    // Validate that all properties marked as required are resolvable:
    // see ConfigurablePropertyResolver#setRequiredProperties
    //验证当前上下文需要的属性是否放入环境中
    getEnvironment().validateRequiredProperties();

    // Store pre-refresh 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...
    this.earlyApplicationEvents = new LinkedHashSet<>();
}

该方法主要做了以下几件事:

• 对当前上下文进行状态的设置.
• 初始化 context environment 中占位符.
• 当前环境的一些校验等.

对于beanFactory的初始化

/**
 * Tell the subclass to refresh the internal bean factory.
 * @return the fresh BeanFactory instance
 * @see #refreshBeanFactory()
 * @see #getBeanFactory()
 */
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    refreshBeanFactory();
    return getBeanFactory();
}

其真正的核心逻辑处理方法为refreshBeanFactory(),接着看:

    AbstractRefreshableApplicationContext.java
/**
 * This implementation performs an actual refresh of this context's underlying
 * bean factory, shutting down the previous bean factory (if any) and
 * initializing a fresh bean factory for the next phase of the context's lifecycle.
 */
@Override
protected final void refreshBeanFactory() throws BeansException {
    //进行判断,若存在,销毁该beanFactory下的所有bean,并对其关闭处理
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    try {
        //创建DefaultListableBeanFactory对象
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        //设置序列化编码
        beanFactory.setSerializationId(getId());
        //定制BeanFactory设置相关属性
        customizeBeanFactory(beanFactory);
        //加载beanDefinition
        loadBeanDefinitions(beanFactory);
        //将beanFactory设置为当前环境下的beanFactory
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    }
    catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }}

简单的来看下上述的过程:

• 首先是对当前容器的判断,如果已存在beanFactory则将其移除该beanFactory创建的bean和移除自身
• 接着是调用#createBeanFactory()方法来创建beanFactory实例
• 给beanfactory设置序列化id
• 加载beanDefinition
• 将创建好的 bean 工厂的引用交给的 context 来管理

prepareBeanFactory(beanFactory)

/**
 * Configure the factory's standard context characteristics,
 * such as the context's ClassLoader and post-processors.
 * @param beanFactory the BeanFactory to configure
 */
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    // Tell the internal bean factory to use the context's class loader etc.
    //设置beanFactory的classLoader为当前上下文的classLoader
    beanFactory.setBeanClassLoader(getClassLoader());
    //设置beanFactory的表达式语言处理器
    //默认可以使用#{bean.xxx}的形式来调用相关属性值
    beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    //为beanFactory增加一个默认的PropertyEditor,主要是针对bean的属性等设置管理统一的一个tool
    beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

    // Configure the bean factory with context callbacks.
    //添加beanPostProcessor
    beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    //设置几个忽略自动装配的接口
    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.
    //设置几个自动装配的特殊规则
    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.
    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.
    // 注册默认的系统环境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());
    }
}

上述代码实际是给beanFactory设置各种各样的功能

postProcessBeanFactory(beanFactory)

protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
}

是在AbstractApplicationContext里是空实现,该方法允许子类覆盖去实现,我们接着看:

#AbstractRefreshableWebApplicationContext.java
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
    beanFactory.ignoreDependencyInterface(ServletContextAware.class);
    beanFactory.ignoreDependencyInterface(ServletConfigAware.class);

    WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
    WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
}

我们可以在子类AbstractRefreshableWebApplicationContext看到了实现的过程,简单的看一下流程:

• 首先是添加ServletContextAwareProcessor到我们的beanFactory容器中,其中processor 实现 BeanPostProcessor 接口,主要用于将ServletContext 传递给实现了 ServletContextAware 接口的 bean.
• 忽略一些装配接口ServletContextAware和ServletConfigAware等.
• 注册 WEB 应用特定的域(scope)到 beanFactory 中，方便WebApplicationContext 可以使用它们,常见的有: request session response application等.
• 注册 WEB 应用特定的 Environment bean 到 beanFactory 中,以便WebApplicationContext 可以使用它们,常见的有:contextAttributes等.

invokeBeanFactoryPostProcessors(beanFactory)

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

    // Invoke BeanDefinitionRegistryPostProcessors first, if any.
    //processedBeans用来保存所有的beanFactoryPostProcessor
    Set<String> processedBeans = new HashSet<>();
    //如果当前的beanFactory为BeanDefinitionRegistry
    if (beanFactory instanceof BeanDefinitionRegistry) {
        //强转为BeanDefinitionRegistry类型的
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
        //BeanFactoryPostProcessor的集合
        List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
        //遍历处理过程
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            //如果是BeanDefinitionRegistryPostProcessor实例
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryProcessor =
                        (BeanDefinitionRegistryPostProcessor) postProcessor;
                //添加到registryProcessors集合中
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            }
            //如果不是BeanDefinitionRegistryPostProcessor,则保存到regularPostProcessors集合中
            else {
                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.
        //用于保存临时的BeanDefinitionRegistryPostProcessor
        List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

        // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
        //首先处理实现了 PriorityOrdered (有限排序接口)的 BeanDefinitionRegistryPostProcessor
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        //遍历处理
        for (String ppName : postProcessorNames) {
            //将ConfigurableListableBeanFactory和PriorityOrdered进行匹配
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                //添加
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }
        //排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        //保存到registryProcessors集合中
        registryProcessors.addAll(currentRegistryProcessors);
        //调用所有实现了PriorityOrdered的BeanDefinitionRegistryPostProcessors的postProcessBeanDefinitionRegistry()
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        //清空,以备下次使用
        currentRegistryProcessors.clear();

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        //其次是调用Ordered的BeanDefinitionRegistryPostProcessors
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            //包含
            if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }
        //排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        registryProcessors.addAll(currentRegistryProcessors);
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();

        // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
        //最后是调用其他的BeanDefinitionRegistryPostProcessors
        boolean reiterate = true;
        while (reiterate) {
            reiterate = false;
            //通过bean的类型去获取BeanDefinitionRegistryPostProcessor
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                //没有包含在processedBeans中的（因为包含了的都已经处理了）
                if (!processedBeans.contains(ppName)) {
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                    reiterate = true;
                }
            }
            //最后与上面的处理过程一样
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            registryProcessors.addAll(currentRegistryProcessors);
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            currentRegistryProcessors.clear();
        }

        // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
        //调用所有的BeanFactoryPostProcessors(这里只包含我们手动注册的)
        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
    }
        //如果不是BeanDefinitionRegistry 只需要调用其回调函数（postProcessBeanFactory()）即可
    else {
        // Invoke factory processors registered with the context instance.
        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!
    String[] postProcessorNames =
            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    //这里需要区分PriorityOrdered和Ordered和no Ordered
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    List<String> orderedPostProcessorNames = new ArrayList<>();
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        //如果包含,直接跳过,表示已经处理过了
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
        }
        //PriorityOrdered类型
        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
        }
        //Ordered类型的
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        //nonOrdered类型的
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
    //首先是调用priorityOrderedPostProcessors接口
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    //接着是Ordered接口
    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.
    //最后是nonOrdered接口处理
    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();
}

上述代码其主要的作用是激活beanFactory的各种处理器,代码有点长,其整个处理逻辑简单清晰,都是对所有的BeanDefinitionRegistryPostProcessors按照PriorityOrdered以及Ordered和ordered的分别处理过程.

registerBeanPostProcessors

该方法主要的作用是注册所有的注册所有的BeanPostProcessor,来看代码:

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

这里并看不到真正的处理过程,接着看:

public static void registerBeanPostProcessors(
        ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

    //获取所有BeanPostProcessor的beanName
    //此时的bean是未进行初始化操作,但已经加载到容器中
    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
    //记录所有beanPostProcessor的数量
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    //注册BeanPostProcessorChecker,其主要的作用是在bean的实例化期间进行日志的记录
    //
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    //通过PriorityOrdered来保证顺序
    List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
    //有顺序
    List<String> orderedPostProcessorNames = new ArrayList<>();
    //没有顺序
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    for (String ppName : postProcessorNames) {
        if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            //获取BeanPostProcessor实例
            BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
            priorityOrderedPostProcessors.add(pp);
            if (pp instanceof MergedBeanDefinitionPostProcessor) {
                internalPostProcessors.add(pp);
            }
        }
        //保存到有序的orderedPostProcessorNames缓存中
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        //保存到无序的缓存中
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    //第一步，注册所有实现了 PriorityOrdered 的 BeanPostProcessor
    //首先是排序
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    //接着是注册
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    //第二步,注册所有实现Ordered接口的BeanPostProcessor
    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);
        }
    }
    //还是先排序
    sortPostProcessors(orderedPostProcessors, beanFactory);
    //接着是注册
    registerBeanPostProcessors(beanFactory, orderedPostProcessors);

    // Now, register all regular BeanPostProcessors.
    //第三步,注册所有没有排序的BeanPostProcessor
    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);
        }
    }
    //注册,这里不需要排序
    registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

    // Finally, re-register all internal BeanPostProcessors.
    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).
    //加入ApplicationListenerDetector(探测器)
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

这里将注册的逻辑委托给PostProcessorRegistrationDelegate来实现,具体的就不在啰嗦了,接着看

initMessageSource

该方法主要是为上下文环境初始化MessageSource,即不同语言的消息体,国际化处理操作,我们来看代码:

protected void initMessageSource() {
    //获取并初始化beanFactory
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    //如果在beanFactory包含messageSource的bean
    if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {
        //直接获取通过getBean(...)方法
        this.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);
        // Make MessageSource aware of parent MessageSource.
        //如果有父类并且是HierarchicalMessageSource类型的
        if (this.parent != null && this.messageSource instanceof HierarchicalMessageSource) {
            //强转为HierarchicalMessageSource
            HierarchicalMessageSource hms = (HierarchicalMessageSource) this.messageSource;
            if (hms.getParentMessageSource() == null) {
                // Only set parent context as parent MessageSource if no parent MessageSource
                // registered already.
                //如果没有注册父 MessageSource,则设置为父类上下文的的 MessageSource
                hms.setParentMessageSource(getInternalParentMessageSource());
            }
        }
        if (logger.isTraceEnabled()) {
            logger.trace("Using MessageSource [" + this.messageSource + "]");
        }
    }
    //这里是beanFactory不包含messageSource该bean
    else {
        // Use empty MessageSource to be able to accept getMessage calls.
        //使用空的MessageSource去接受message
        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 + "]");
        }
    }
}

代码逻辑简单,根据获取到的beanFactorey来区分,如果包含messageSource的bean进行相应的处理,没有的使用空的MessageSource来进行消息的处理,接着看:

initApplicationEventMulticaster

该方法的主要作用是为当前上下文来初始化一个事件广播器,我们来看代码:

/**
 * Initialize the ApplicationEventMulticaster.
 * Uses SimpleApplicationEventMulticaster if none defined in the context.
 * @see org.springframework.context.event.SimpleApplicationEventMulticaster
 */
protected void initApplicationEventMulticaster() {
    //获取ConfigurableListableBeanFactory从BeanFactory中
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    //如果包含applicationEventMulticaster类型的bean
    if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
        //直接获取初始化
        this.applicationEventMulticaster =
                beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
        if (logger.isTraceEnabled()) {
            logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
        }
    }
    //没有则新建SimpleApplicationEventMulticaster,并完成 bean的注册
    else {
        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() + "]");
        }
    }
}

可以发现跟消息的初始化类似,我们接着看:

onRefresh

该方法主要是留给子类拓展方法,用来完成其他bean的上下文刷新操作

/**
 * Template method which can be overridden to add context-specific refresh work.
 * Called on initialization of special beans, before instantiation of singletons.
 * <p>This implementation is empty.
 * @throws BeansException in case of errors
 * @see #refresh()
 */
protected void onRefresh() throws BeansException {
    // For subclasses: do nothing by default.
}

所以是空实现喽

registerListeners

该方法其主要的作用是为当前上下文注册一个事件监听器,至于监听器从何而来,是在所有的bean中去找,那么注册到哪呢?则是广播器中,我们来看代码:

/**
 * Add beans that implement ApplicationListener as listeners.
 * Doesn't affect other listeners, which can be added without being beans.
 */
protected void registerListeners() {
    // 首先是注册静态监听器
    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!
    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...
    //至此,已经完成将监听器注册到ApplicationEventMulticaster中,下面将发布前期的事件给监听器
    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
    this.earlyApplicationEvents = null;
    if (earlyEventsToProcess != null) {
        for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
            getApplicationEventMulticaster().multicastEvent(earlyEvent);
        }
    }
}

finishBeanFactoryInitialization

该方法主要的作用是初始化剩下的单例Bean(非延迟加载的),来看代码:

/**
 * Finish the initialization of this context's bean factory,
 * initializing all remaining singleton beans.
 */
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
    // 给当前上下文初始化转换器服务
    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.
    //如果之前没有注册 bean 后置处理器（例如PropertyPlaceholderConfigurer）,则注册默认的解析器
    if (!beanFactory.hasEmbeddedValueResolver()) {
        beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
    }

    // 尽早初始化LoadTimeWeaverAware bean以允许尽早注册其变换器
    String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
    for (String weaverAwareName : weaverAwareNames) {
        getBean(weaverAwareName);
    }

    // 停止使用临时的 ClassLoader
    beanFactory.setTempClassLoader(null);

    // 允许缓存所有bean定义元数据
    beanFactory.freezeConfiguration();

    // 初始化所有剩余的单例(非延迟的).
    beanFactory.preInstantiateSingletons();
}

finishRefresh

该方法为refresh的最后一个方法其主要的作用是完成刷新过程,通知生命周期处理器lifecycleProcessor刷新过程,同时发出ContextRefreshEvent通知别人,我们来看代码:

/**
 * 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);
}

我们可以看到的在方法finishRefresh()中是做了一些完成上下文刷新后的工作,就像代码中的清空资源缓存以及初始化生命周期等等操作,那么本节到这里就完了,关于APPlicationContext高级容器我们就说这么多,下节我们来说spring的另一个很吊的作用AOP...