Spring源码之ApplicationContext

​ 本文是针对Srping的ClassPathXMLApplicationContext来进行源码解析,在本篇博客中将不会讲述spring Xml解析注册代码，因为ApplicationContext是BeanFactory的扩展版本ApplicationContext的GetBean和xml解析注册BeanDefinition都是用一套代码，如果您是第一次看请先看一下XMLBeanFactory解析和BeanFactory.GetBean源码解析：

• XMLBeanFactory源码解析地址： https://blog.csdn.net/qq_3025...
• BeanFactory.getBean源码解析地址： https://blog.csdn.net/qq_3025...

作者整理了spring-framework 5.x的源码注释，代码已经上传者作者的GitHub了，可以让读者更好的理解，地址：

• GItHub: https://github.com/lantaoGitH...

• 接下来我们你直接上源码：

package lantao;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.lantao.UserBean;

public class ApplicationContextTest {

    public static void main(String[] args) {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-bean.xml");
        UserBean userBean = (UserBean) applicationContext.getBean("userBean");
        System.out.println(userBean.getName());
    }

}

在这里直接使用ClassPathXmlApplicationContext进行xml解析，在这里xml解析的代码和GetBean的代码就不过多的描述了，ApplicationContext是BeanFactory的扩展，所以想要看这两部分源码的请看作者的上两篇博客Sprin源码解析；

• 接下来我们看一下ClassPathXmlApplicationContext的源码：

/**
 * Create a new ClassPathXmlApplicationContext with the given parent,
 * loading the definitions from the given XML files.
 * @param configLocations array of resource locations
 * @param refresh whether to automatically refresh the context,
 * loading all bean definitions and creating all singletons.
 * Alternatively, call refresh manually after further configuring the context.
 * @param parent the parent context
 * @throws BeansException if context creation failed
 * @see #refresh()
 */
public ClassPathXmlApplicationContext(
        String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
        throws BeansException {

    super(parent);
    // 支持解析多文件
    setConfigLocations(configLocations);
    if (refresh) {
        refresh();
    }
}

在setConfigLocations方法中将资源文件放入configLocations全局变量中，，并且支持多文件解析，接下来我们你看一下重点，refresh方法；

• 源码refresh方法：

@Override
public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        // Prepare this context for refreshing.
        // 准备刷新上下文
        prepareRefresh();

        // Tell the subclass to refresh the internal bean factory.
        // 对beanFactory的各种功能填充，加载beanFactory，经过这个方法 applicationContext就有了BeanFactory的所有功能
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

        // Prepare the bean factory for use in this context.
        // 对beanFactory进行各种功能填充
        prepareBeanFactory(beanFactory);

            try {
            // Allows post-processing of the bean factory in context subclasses.
            //  允许在context子类中对BeanFactory进行post-processing。
            // 允许在上下文子类中对Bean工厂进行后处理
            // 可以在这里进行 硬编码形式的 BeanFactoryPostProcessor 调用 addBeanFactoryPostProcessor
            postProcessBeanFactory(beanFactory);

            // Invoke factory processors registered as beans in the context.
            // 激活各种BeanFactory处理器 BeanFactoryPostProcessors是在实例化之前执行
            invokeBeanFactoryPostProcessors(beanFactory);

            // Register bean processors that intercept bean creation.
            // 注册 拦截Bean创建 的Bean处理器，这里只是注册，真正地调用在getBean的时候  BeanPostProcessors实在init方法前后执行 doCreateBean方法中的 实例化方法中执行
            // BeanPostProcessor执行位置：doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization 和 applyBeanPostProcessorsAfterInitialization
            registerBeanPostProcessors(beanFactory);

            // Initialize message source for this context.
            //为上下文初始化Message源，（比如国际化处理） 这里没有过多深入
            initMessageSource();

            // Initialize event multicaster for this context.
            //初始化应用消息广播，并放入 applicationEventMulticaster bean中
            initApplicationEventMulticaster();

            // Initialize other special beans in specific context subclasses.
            //留给子类来初始化其它的bean
            onRefresh();

            // Check for listener beans and register them.
            //在所有注册的bean中查找Listener bean，注册到消息广播器中
            registerListeners();

            // Instantiate all remaining (non-lazy-init) singletons.
            //初始化剩下的单实例
            finishBeanFactoryInitialization(beanFactory);

            // Last step: publish corresponding event.
            //完成刷新过程，通知生命周期护处理器lifecycleProcessor刷新过程，同时发出ContextRefreshEvent通知别人（LifecycleProcessor 用来与所有声明的bean的周期做状态更新）
            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();
        }
    }
}

• 先来看prepareRefresh方法：

/**
 * 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.
    this.startupDate = System.currentTimeMillis();
    // 标志，指示是否已关闭此上下文
    this.closed.set(false);
    // 指示此上下文当前是否处于活动状态的标志
    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.
    // 对上下文环境中的任何属性源进行分类。
    initPropertySources();

    // Validate that all properties marked as required are resolvable:
    // see ConfigurablePropertyResolver#setRequiredProperties，

    //验证标示为必填的属性信息是否都有了 ConfigurablePropertyResolver#setRequiredProperties 方法
    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<>();
}

public class MyClassPathXmlApplicationContext extends ClassPathXmlApplicationContext{
      public MyClassPathXmlApplicationContext(String.. configLocations){
            super(configLocations);
       }
       protected void initPropertySources(){
             //添加验证要求
             getEnvironment().setRequiredProterties("VAR")；
       }
}

public static void main(Stirng[] args){
   ApplicationContext bf = new MyClassPathXmlApplicationContext("myTest.xml")；
   User user = (User)bf.getBean("testBean");
   }

• 接下来看一下obtainFreshBeanFactory方法，在这里初始化DefaultListAbleBeanFactory并解析xml：

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

/**
 * 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 {
    if (hasBeanFactory()) {
        destroyBeans();
        closeBeanFactory();
    }
    try {
        // createBeanFactory方法直接新建一个DefaultListableBeanFactory，内部使用的是DefaultListableBeanFactory实例
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        // 设置序列化id
        beanFactory.setSerializationId(getId());
        // 定制beanFactory工厂
        customizeBeanFactory(beanFactory);
        // 加载BeanDefinition
        loadBeanDefinitions(beanFactory);
        synchronized (this.beanFactoryMonitor) {
            // 使用全局变量记录BeanFactory
            this.beanFactory = beanFactory;
        }
    }
    catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
}

package lantao;
  import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyApplicationContext extends ClassPathXmlApplicationContext {

    public MyApplicationContext(String... configLocations){
       super(configLocations);
    }
    protected void initPropertySources(){
        //添加验证要求
        getEnvironment().setRequiredProperties("VAR");
    
                // 在这里添加set
        super.setAllowBeanDefinitionOverriding(true);
        super.setAllowCircularReferences(true);
    }
}

• 下面看一下prepareBeanFactory方法源码：

/**
 * 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context的classloader
    beanFactory.setBeanClassLoader(getClassLoader());

    // Spel语言解析器
    // 设置BeanFactory的表达式语言处理器 Spring3中增加了表达式语言的支持
    // 默认可以使用#{bean.xxx}的形式来调用相关属性值
    // 在Bean实例化的时候回调用 属性填充的方法(doCreateBean 方法中的 populateBean 方法中的 applyPropertyValues 方法中的 evaluateBeanDefinitionString ) 就会判断beanExpressionResolver是否为null操作
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));

    // 为BeanFactory增加一个默认的 PropertyEditor 这个主要对bean的属性等设置管理的一个工具 增加属性注册编辑器  例如：bean property 类型 date 则需要这里
    // beanFactory会在初始化 BeanWrapper（initBeanWrapper）中调用 ResourceEditorRegistrar 的 registerCustomEditors 方法
    beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

    // Configure the bean factory with context callbacks.
    // ApplicationContextAwareProcessor --> postProcessBeforeInitialization
    // 注册 BeanPostProcessor  BeanPostProcessor 实在实例化前后执行的
    beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));

    // 设置几个忽略自动装配的接口 在addBeanPostProcessor方法中已经对下面几个类做了处理，他们就不是普通的bean了，所以在这里spring做bean的依赖的时候忽略
    // doCreateBean 方法中的 populateBean 方法中的 autowireByName 或 autowireByType 中的 unsatisfiedNonSimpleProperties 中的  !isExcludedFromDependencyCheck(pd) 判断，
    // 在属性填充的时候回判断依赖，如果存在下属几个则不做处理 对于下面几个类可以做implements操作
    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.
    // 设置几个注册依赖 参考spring源码深度解析原文：当注册依赖解析后，例如但那个注册了对BeanFactory。class的解析依赖后，当bean的属性注入的时候，一旦检测到属性为BeanFactory的类型变回将beanFactory 实例注入进去
    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.
    // 寄存器早期处理器，用于检测作为ApplicationListener的内部bean。
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

    // Detect a LoadTimeWeaver and prepare for weaving, if found.
    // 增加了对AxpectJ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.
    // 添加默认的系统环境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());
    }
}

@Override
   @Nullable
   public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
       AccessControlContext acc = null;
   
       // 该方法也会在 BeanFactory 实例化bean 中调用  doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization --> postProcessBeforeInitialization
       // 如果实例化的类实现了 invokeAwareInterfaces 方法中的判断类 则会调用初始方法赋值
       if (System.getSecurityManager() != null &&
               (bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
                       bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
                       bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
           acc = this.applicationContext.getBeanFactory().getAccessControlContext();
       }
   
       if (acc != null) {
           AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
               invokeAwareInterfaces(bean);
               return null;
           }, acc);
       }
       else {
           invokeAwareInterfaces(bean);
       }
           return bean;
   }
   private void invokeAwareInterfaces(Object bean) {
       if (bean instanceof Aware) {
           if (bean instanceof EnvironmentAware) {
               ((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
           }
           if (bean instanceof EmbeddedValueResolverAware) {
               ((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
           }
           if (bean instanceof ResourceLoaderAware) {
               ((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
           }
           if (bean instanceof ApplicationEventPublisherAware) {
               ((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
           }
           if (bean instanceof MessageSourceAware) {
               ((MessageSourceAware) bean).setMessageSource(this.applicationContext);
           }
           if (bean instanceof ApplicationContextAware) {
               ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
           }
       }
   }
   
   @Override
   public Object postProcessAfterInitialization(Object bean, String beanName) {
       return bean;
   }

• 上述就是对BeanFactory的功能填充，下面看postProcessBeanFactory:

postProcessBeanFactory方法是个空方法，允许在上下文子类中对Bean工厂进行后处理，例如：可以在这里进行 硬编码形式的 BeanFactoryPostProcessor 调用 addBeanFactoryPostProcessor，进行addBeanFactoryPostProcessor或者是BeanPostProcessor；

• 接下来看一下invokeBeanFactoryPostProcessors方法:

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

    // Invoke BeanDefinitionRegistryPostProcessors first, if any.
    Set<String> processedBeans = new HashSet<>();

    // 对 BeanDefinitionRegistry  类型处理
    if (beanFactory instanceof BeanDefinitionRegistry) {
        // 强转
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

        // 普通的处理器
        List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();

        //注册处理器
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();


        // 这里就是硬编码处理 因为这里是从 getBeanFactoryPostProcessors()方法获取的 可以硬编码从addBeanFactoryPostProcessor（）方法添加
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {

            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {

                // 对于 BeanDefinitionRegistryPostProcessor 类型 在 BeanFactoryPostProcessor 的基础上还有自己的定义，需要先调用
                BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor;

                // 执行 继承 BeanDefinitionRegistryPostProcessor 类的  postProcessBeanDefinitionRegistry 方法
                registryProcessor.postProcessBeanDefinitionRegistry(registry);

                registryProcessors.add(registryProcessor);
            }
            else {
                regularPostProcessors.add(postProcessor);
            }
        }
        //上边的For循环只是调用了硬编码的 BeanDefinitionRegistryPostProcessor 中的 postProcessBeanDefinitionRegistry 方法，
        // 但是 BeanFactoryPostProcessor 中的 postProcessBeanFactory 方法还没有调用，是在方法的最后一行
        // invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
        // invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); 这两个方法中执行的，


        // 下面是自动处理器 获取类型是BeanDefinitionRegistryPostProcessor  beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); 获取的


        // 当前注册处理器
        List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

        // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
        // 首先调用实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessors
        String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);

        for (String ppName : postProcessorNames) {
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        registryProcessors.addAll(currentRegistryProcessors);
        // 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        // 下一个 ，调用实现 Ordered 的 BeanDefinitionRegistryPostProcessors
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        registryProcessors.addAll(currentRegistryProcessors);
        // 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();

        // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
        // 最后，调用所有其他BeanDefinitionRegistryPostProcessors，直到不再显示其他BeanDefinitionRegistryPostProcessors 无序的
        boolean reiterate = true;
        while (reiterate) {
            reiterate = false;
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                if (!processedBeans.contains(ppName)) {
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                    reiterate = true;
                }
            }
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            registryProcessors.addAll(currentRegistryProcessors);
            // 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                currentRegistryProcessors.clear();
        }

        // 现在，调用到目前为止处理的所有处理器的  执行BeanFactoryPostProcessor 类的 postProcessBeanFactory 方法
        // 这里执行的是 硬编码 和 非硬编码（自动）的 BeanFactoryPostProcessor 类的 postProcessBeanFactory 方法 分为硬编码处理器 和 普通处理器
        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
    }

    else {
        // 调用在上下文实例中注册的工厂处理器的postProcessBeanFactory方法。 就是硬编码 通过 addBeanFactoryPostProcessor 方法添加的BeanFactoryPostProcessor
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
    }




    // 自动处理 非硬编码 获取类型为是BeanFactoryPostProcessor    beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

    // 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.

    //  实现 priorityOrdered 的
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();

    // 实现 Ordered 的
    List<String> orderedPostProcessorNames = new ArrayList<>();

    // 无序的
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();

    for (String ppName : postProcessorNames) {
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
        }
        else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
    for (String postProcessorName : orderedPostProcessorNames) {
        orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
    }
    sortPostProcessors(orderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

    // Finally, invoke all other BeanFactoryPostProcessors.
    List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
    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();
}

• registerBeanPostProcessors方法源码：

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

    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.
    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // Separate between BeanPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
    // 使用 priorityOrdered保证顺序
    List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();

    // MergedBeanDefinitionPostProcessor
    List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();

    // 使用order保证顺序
    List<String> orderedPostProcessorNames = new ArrayList<>();

    // 无序的
    List<String> nonOrderedPostProcessorNames = new ArrayList<>();

    // 进行add操作
    for (String ppName : postProcessorNames) {
        if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
            priorityOrderedPostProcessors.add(pp);
            if (pp instanceof MergedBeanDefinitionPostProcessor) {
                internalPostProcessors.add(pp);
            }
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, register the BeanPostProcessors that implement PriorityOrdered.
    // 首先 注册实现PriorityOrdered的 BeanPostProcessors 先排序PostProcessors
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // Next, register the BeanPostProcessors that implement Ordered.
    // 下一个，注册实现Ordered的BeanPostProcessors
    List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
    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.
    // 现在，注册所有常规注册。无序的
    List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
    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.
    // 最后，注册所有MergedBeanDefinitionPostProcessor类型的BeanPostProcessor,并非重复注册。
    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 ApplicationListener探测器
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

• 接下来是initMessageSource方法，这里作者没有过多的看源码，后续补上吧.......(抱歉)

• initApplicationEventMulticaster源码：

/**
 * Initialize the ApplicationEventMulticaster.
 * Uses SimpleApplicationEventMulticaster if none defined in the context.
 * @see org.springframework.context.event.SimpleApplicationEventMulticaster
 */
protected void initApplicationEventMulticaster() {
    ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    // 使用自定义的 广播
    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 {
        // 使用spring 默认的广播
        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() + "]");
        }
    }
}

initApplicationEventMulticaster方法中主要就是判断是使用自定义的ApplicationEventMulticaster(广播器)还是使用呢Spring默认的SimpleApplicationEventMulticaster广播器；

• onRefresh 方法是留个子类重写的，内容是空；
• registerListeners方法：

/**
 * 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.
    // 注册 添加 ApplicationListener  这里通过硬编码 addApplicationListener 方法添加的
    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!
    // 注册 添加 ApplicationListener 这里是自动注册添加的
    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...
    // 发布早期的事件
    Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
    this.earlyApplicationEvents = null;
    if (earlyEventsToProcess != null) {
        for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
            getApplicationEventMulticaster().multicastEvent(earlyEvent);
        }
    }
}

• finishBeanFactoryInitialization方法源码：

/**
 * 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.
    // conversionService 用于类型转换 ，比如 String 转Date
    //判断BeanFactory中是否存在名称为“conversionService”且类型为ConversionService的Bean，如果存在则将其注入到beanFactory
    // 判断有无自定义属性转换服务接口，并将其初始化，我们在分析bean的属性填充过程中，曾经用到过该服务接口。在TypeConverterDelegate类的convertIfNecessary方法中
    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.
    // 得到所有的实现了LoadTimeWeaverAware接口的子类名称，初始化它们
    // 如果有LoadTimeWeaverAware类型的bean则初始化，用来加载Spring Bean时织入第三方模块,如AspectJ，我们在后面详细讲解。
    String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
    for (String weaverAwareName : weaverAwareNames) {
        getBean(weaverAwareName);
    }

    // Stop using the temporary ClassLoader for type matching.
    // 停止使用临时类加载器 就是在这里不让使用呢 ClassLoader 了
    beanFactory.setTempClassLoader(null);

    // Allow for caching all bean definition metadata, not expecting further changes.
    // 冻结所有bean定义，说明你注册的bean将不被修改或进行任何进一步的处理 就是不让改了 BeanDefinition
    beanFactory.freezeConfiguration();

    // Instantiate all remaining (non-lazy-init) singletons.
    // 初始化所有非懒加载的 单例 bean  调用你getBean方法
    beanFactory.preInstantiateSingletons();
}

• 最后的一个方法finishRefresh：

/**
 * 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).
    // 清除 下文级资源(例如扫描的元数据)。
    clearResourceCaches();
    
    // Initialize lifecycle processor for this context.
    // 在当前context中初始化 lifecycle
    // lifecycle 有自己的 start/ stop方法，实现此接口后spring保证在启动的时候调用start方法开始生命周期 关闭的时候调用 stop方法结束生命周期
    initLifecycleProcessor();

    // Propagate refresh to lifecycle processor first.
    // onRefresh 启动所有实现了 lifecycle 的方法
    getLifecycleProcessor().onRefresh();

    // Publish the final event.
    // 当ApplicationContext初始化完成发布后发布事件 处理后续事宜
    publishEvent(new ContextRefreshedEvent(this));

    // Participate in LiveBeansView MBean, if active.
    // 这里 没明白》。。
    LiveBeansView.registerApplicationContext(this);
}

至此ApplicationContext的源码就都已经分析完成了，其中有很多地方很难懂，大家可以对应着源码一起看，会好理解一些，如果其中有错误，欢迎大神指点，在下方留言，本篇博客是作者参考SPring 源码深度解析 + 自己的理解写出来的，算是一个学习后的的产出，最后，码字不易，转载请注明出处。

博客地址： http://lantaoblog.site