Spring源码解析 – AnnotationConfigApplicationContext容器创建过程

Bertha 。 2022-01-16 23:17 314阅读 0赞

# [Spring源码解析 – AnnotationConfigApplicationContext容器创建过程][Spring_ _ AnnotationConfigApplicationContext] #

Spring在BeanFactory基础上提供了一些列具体容器的实现，其中AnnotationConfigApplicationContext是一个用来管理注解bean的容器，从AnnotationConfigApplicationContext的实现结构图中可以看出：

*  AnnotationConfigApplicationContext继承GenericApplicationContext这个通用应用上下文，GenericApplicationContext内部定义了一个DefaultListableBeanFactory实例，GenericApplicationContext实现了BeanDefinitionRegistry接口，所以可以通过AnnotationConfigApplicationContext实例注册bean defintion，然后调用refresh()方法来初始化上下文。
 *  AnnotationConfigApplicationContext继承AbstractApplicationContext，AbstractApplicationContext提供了ApplicationContext的抽象实现。

下面通过一个示例分析AnnotationConfigApplicationContext的初始化过程：

AnnotationConfigApplicationContext applicationContext  = new AnnotationConfigApplicationContext(ExtensionConfig.class);

构造函数：

//1. 初始化bean读取器和扫描器;
         //调用父类GenericApplicationContext无参构造函数，初始化一个BeanFactory: 
         //DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory()
        this();
        //2.注册bean配置类
        register(annotatedClasses);
        //3.刷新上下文
        refresh();
     }

# 1. this() 初始化bean读取器和扫描器 #

public AnnotationConfigApplicationContext() {
         //在IOC容器中初始化一个 注解bean读取器AnnotatedBeanDefinitionReader
        this.reader = new AnnotatedBeanDefinitionReader(this);
        //在IOC容器中初始化一个 按类路径扫描注解bean的 扫描器
        this.scanner = new ClassPathBeanDefinitionScanner(this);

GenericApplicationContext部分代码:

public class GenericApplicationContext extends AbstractApplicationContext implements BeanDefinitionRegistry {
     private final DefaultListableBeanFactory beanFactory;
     
     //初始化一个BeanFactory
     public GenericApplicationContext() {
           this.beanFactory = new DefaultListableBeanFactory();
         }
     
         …
     }

# 2. register(annotatedClasses) #

注册bean配置类, AnnotationConfigApplicationContext容器通过AnnotatedBeanDefinitionReader的register方法实现注解bean的读取，具体源码如下：

AnnotationConfigApplicationContext.java中register方法

//按指定bean配置类读取bean
     public void register(Class<?>... annotatedClasses) {
        for (Class<?> annotatedClass : annotatedClasses) {
           registerBean(annotatedClass);
        }
     }
     
     public void registerBean(Class<?> annotatedClass) {
        doRegisterBean(annotatedClass, null, null, null);
     }
     
     //核心实现逻辑
     <T> void doRegisterBean(Class<T> annotatedClass, @Nullable Supplier<T> instanceSupplier, @Nullable String name,
           @Nullable Class<? extends Annotation>[] qualifiers, BeanDefinitionCustomizer... definitionCustomizers) {
        //将Bean配置类信息转成容器中AnnotatedGenericBeanDefinition数据结构, 
        //AnnotatedGenericBeanDefinition继承自BeanDefinition作用是定义一个bean的数据结构，下面的
        //getMetadata可以获取到该bean上的注解信息
        AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass);
         //@Conditional装配条件判断是否需要跳过注册
        if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
           return;
        }
        //@param instanceSupplier a callback for creating an instance of the bean
        //设置回调
        abd.setInstanceSupplier(instanceSupplier);
        //解析bean作用域(单例或者原型)，如果有@Scope注解，则解析@Scope，没有则默认为singleton 
        ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
     　　//作用域写回BeanDefinition数据结构, abd中缺损的情况下为空，将默认值singleton重新赋值到abd
        abd.setScope(scopeMetadata.getScopeName());
     　　//生成bean配置类beanName
        String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
        //通用注解解析到abd结构中，主要是处理Lazy, primary DependsOn, Role ,Description这五个注解
        AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
     　　//@param qualifiers specific qualifier annotations to consider, if any, in addition to qualifiers at the bean class level
     　　// @Qualifier特殊限定符处理，
        if (qualifiers != null) {
           for (Class<? extends Annotation> qualifier : qualifiers) {
              if (Primary.class == qualifier) {
         // 如果配置@Primary注解，则设置当前Bean为自动装配autowire时首选bean
                 abd.setPrimary(true);
              }
     　　else if (Lazy.class == qualifier) {
     　　//设置当前bean为延迟加载
                 abd.setLazyInit(true);
              }
              else {
     　　　　　　//其他注解，则添加到abd结构中
                 abd.addQualifier(new AutowireCandidateQualifier(qualifier));
              }
           }
        }
     　　//自定义bean注册，通常用在applicationContext创建后，手动向容器中以lambda表达式的方式注册bean, 
     　　//比如：applicationContext.registerBean(UserService.class, () -> new UserService());
        for (BeanDefinitionCustomizer customizer : definitionCustomizers) {
    　　　　 //自定义bean添加到BeanDefinition
           customizer.customize(abd);
        }
        //根据beanName和bean定义信息封装一个beanhold,heanhold其实就是一个 beanname和BeanDefinition的映射
        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
     　　//创建代理对象
        definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
     　　// BeanDefinitionReaderUtils.registerBeanDefinition 
         //内部通过DefaultListableBeanFactory.registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
         //按名称将bean定义信息注册到容器中，
     　  // 实际上DefaultListableBeanFactory内部维护一个Map<String, BeanDefinition>类型变量
        //beanDefinitionMap，用于保存注bean定义信息（beanname 和 beandefine映射）
        BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
     }

register方法重点完成了bean配置类本身的解析和注册，处理过程可以分为以下几个步骤：

1.  根据bean配置类，使用BeanDefinition解析Bean的定义信息，主要是一些注解信息
2.  Bean作用域的处理，默认缺少@Scope注解，解析成单例
3.  借助AnnotationConfigUtils工具类解析通用注解
4.  将bean定义信息已beanname，beandifine键值对的形式注册到ioc容器中

# 3. refresh()刷新上下文 #

refresh方法在AbstractApplicationContext容器中实现，refresh()方法的作用加载或者刷新当前的配置信息，如果已经存在spring容器，则先销毁之前的容器，重新创建spring容器，载入bean定义，完成容器初始化工作，所以可以看出AnnotationConfigApplicationContext容器是通过调用其父类AbstractApplicationContext的refresh()函数启动整个IoC容器完成对Bean定义的载入。

AbstractApplicationContext.java中refresh方法的实现代码如下：

public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
           //1.刷新前的预处理
           prepareRefresh();
     
           //2.获取刷新后的内部Bean工厂
           ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
     
           //3.BeanFactory的预准备工作
           prepareBeanFactory(beanFactory);
     
           try {
              // BeanFactory准备工作完成后，可以做一些后置处理工作，
     　　　　  // 4.空方法，用于在容器的子类中扩展
              postProcessBeanFactory(beanFactory);
     
              // 5. 执行BeanFactoryPostProcessor的方法，BeanFactory的后置处理器，在BeanFactory标准初始化之后执行的
              invokeBeanFactoryPostProcessors(beanFactory);
     
              // 6. 注册BeanPostProcessor（Bean的后置处理器）,用于拦截bean创建过程
              registerBeanPostProcessors(beanFactory);
     
              // 7. 初始化MessageSource组件（做国际化功能；消息绑定，消息解析）
              initMessageSource();
     
              // 8. 初始化事件派发器
              initApplicationEventMulticaster();
     
              // 9.空方法，可以用于子类实现在容器刷新时自定义逻辑
              onRefresh();
     
              // 10. 注册时间监听器，将所有项目里面的ApplicationListener注册到容器中来
              registerListeners();
     
              // 11. 初始化所有剩下的单实例bean,单例bean在初始化容器时创建，原型bean在获取时（getbean）时创建
              finishBeanFactoryInitialization(beanFactory);
     
              // 12. 完成BeanFactory的初始化创建工作，IOC容器就创建完成；
              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();
           }
        }
     }

##  ##

## 具体分析refresh中的函数逻辑： ##

### 3.1  刷新预处理： ###

AbstractApplicationContext. prepareRefresh ()方法:

protected void prepareRefresh() {
     　　//设置容器启动时间
        this.startupDate = System.currentTimeMillis();
     　　//启动标识
        this.closed.set(false);
        this.active.set(true);
     
        if (logger.isInfoEnabled()) {
           logger.info("Refreshing " + this);
        }
     
        //空方法，用于子容器自定义个性化的属性设置方法
        initPropertySources();
        //检验属性的合法等
        getEnvironment().validateRequiredProperties();
     
        //保存容器中的一些早期的事件
        this.earlyApplicationEvents = new LinkedHashSet<>();
     }

### 3.2  获取刷新后的内部Bean工厂，obtainFreshBeanFactory方法为内部bean工厂重新生成id，并返回bean工厂 ###

AbstractApplicationContext. obtainFreshBeanFactory()方法

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
     　　//为beanfactory生成唯一序列化id，beanfactory已经在GenericApplicationContext构造函数中初始化了，
        //refreshBeanFactory的逻辑在AbstractApplicationContext的实现类GenericApplicationContext中
        refreshBeanFactory();
    　　 //获取beanfactory
        ConfigurableListableBeanFactory beanFactory = getBeanFactory();
        if (logger.isDebugEnabled()) {
           logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
        }
        return beanFactory;
     }

GenericApplicationContext.refreshBeanFactory()实现代码

protected final void refreshBeanFactory() throws IllegalStateException {
        if (!this.refreshed.compareAndSet(false, true)) {
           throw new IllegalStateException(
                 "GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
        }
     　　//生成一个序列化id
        this.beanFactory.setSerializationId(getId());
     }

这里使用AbstractApplicationContext. refreshBeanFactory()在不同实现容器中有点区别，如果是以xml方式配置bean，会使用AbstractRefreshableApplicationContext容器中的实现，该容器中实现xml配置文件定位，并通过BeanDefinition载入和解析xml配置文件。

而如果是注解的方式，则并没有解析项目包下的注解，而是通过在refresh()方法中执行ConfigurationClassPostProcessor后置处理器完成对bean的加载.

### 3.3  BeanFactory的预准备工作 ###

prepareBeanFactory主要完成beanFactory的一些属性设置

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        // Tell the internal bean factory to use the context's class loader etc.
        beanFactory.setBeanClassLoader(getClassLoader());  //设置类加载器
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader())); //bean表达式解析器
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
     
        // Configure the bean factory with context callbacks.
    	  //添加一个BeanPostProcessor实现ApplicationContextAwareProcessor
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));  
    	  //设置忽略的自动装配接口，表示这些接口的实现类不允许通过接口自动注入
        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.
        //注册可以自动装配的组件，就是可以在任何组件中允许自动注入的组件
        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));
     
        //添加编译时的AspectJ
        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()));
        }
     
        // 给beanfactory容器中注册组件ConfigurableEnvironment、systemProperties、systemEnvironment
        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());
        }
     }

### 3.4  invokeBeanFactoryPostProcessors 执行bean工厂后置处理器 ###

AbstractApplicationContext. invokeBeanFactoryPostProcessors方法实现：

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()));
        }
     }

invokeBeanFactoryPostProcessors方法内部执行实现了BeanFactoryPostProcessor、BeanDefinitionRegistryPostProcessor这两个接口的Processor，先获取所有BeanDefinitionRegistryPostProcessor的实现，按优先级执行（是否实现PriorityOrdered优先级接口，是否实现Ordered顺序接口）；再以相同的策略执行所有BeanFactoryPostProcessor的实现。

PostProcessorRegistrationDelegate. invokeBeanFactoryPostProcessors实现:

public static void invokeBeanFactoryPostProcessors(
           ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
     
        // Invoke BeanDefinitionRegistryPostProcessors first, if any.
        Set<String> processedBeans = new HashSet<>();
     
        if (beanFactory instanceof BeanDefinitionRegistry) {
           BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
           List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
           List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
     
           for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
              if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                 BeanDefinitionRegistryPostProcessor registryProcessor =
                       (BeanDefinitionRegistryPostProcessor) postProcessor;
                 registryProcessor.postProcessBeanDefinitionRegistry(registry);
                 registryProcessors.add(registryProcessor);
              }
              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.
           List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
     
           // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
           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);
           invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
           currentRegistryProcessors.clear();
     
           // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
           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);
           invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
           currentRegistryProcessors.clear();
     
           // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
           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);
              invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
              currentRegistryProcessors.clear();
           }
     
           // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
           invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
           invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        }
     
        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.
        List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
        List<String> orderedPostProcessorNames = new ArrayList<>();
        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();
     }

这里面在处理BeanDefinitionRegistryPostProcessors时有一个非常重要的过程，AnnotationConfigApplicationContext构造函数在初始化reader时为内部beanFactory容器初始化了一个id为org.springframework.context.annotation.internalConfigurationAnnotationProcessor的组件，这是一个ConfigurationClassPostProcessor组件，用来处理添加@Configuration注解的类，并将Bean定义注册到BeanFactory中。

### 3.5  注册BeanPostProcessor（Bean的后置处理器）,用于拦截bean创建过程 ###

注册后置处理器的大致逻辑是：

1.获取所有的 BeanPostProcessor

2.根据处理器实现的接口区分出4中类型：

a.实现PriorityOrdered接口的处理器

b.实现Ordered接口的处理器，

c.实现MergedBeanDefinitionPostProcessor接口的处理器，

d.普通后置处理器

3.按这个4中类型依次注册到容器中

4.注册一个特殊的后置处理器ApplicationListenerDetector，ApplicationListenerDetector本身也实现了MergedBeanDefinitionPostProcessor接口，有个问题，这个为什么没有在上面c,d之间注册，而是放到最后？

AbstractApplicationContext .registerBeanPostProcessors(beanFactory);实现逻辑：

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

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.                                                                                     
        //按优先级分类                                                                                                         
        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);                            
              priorityOrderedPostProcessors.add(pp);                                                                  
              if (pp instanceof MergedBeanDefinitionPostProcessor) {                                                  
                 internalPostProcessors.add(pp);                                                                      
              }                                                                                                       
           }                                                                                                          
           else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {                                                 
              orderedPostProcessorNames.add(ppName);                                                                  
           }                                                                                                          
           else {                                                                                                     
              nonOrderedPostProcessorNames.add(ppName);                                                               
           }                                                                                                          
        }                                                                                                             
                                                                                                                      
        //先注册实现PriorityOrdered接口的处理器，添加到beanfactory容器中 
        beanFactory.addBeanPostProcessor(postProcessor);                
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);                                               
        registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);                                       
                                                                                                                      
        //注册实现Ordered接口的处理器                                                                                           
        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);                                               
                                                                                                                      
        // 注册没有实现Ordered或PriorityOrdered的处理器（nonOrderedPostProcessors）                                                
        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，重新注册所有internal BeanPostProcessors（实现MergedBeanDefinitionPostProcessor接口的后置处理器                             
        sortPostProcessors(internalPostProcessors, beanFactory);                                                      
        registerBeanPostProcessors(beanFactory, internalPostProcessors);                                              
                                                                                                                      
        //注册ApplicationListenerDetector，用于Bean创建完时检查是否是ApplicationListener                                            
        beanFactory.addBeanPostProcessor(new 
        ApplicationListenerDetector(applicationContext));                        
     }

### 3.6  初始化MessageSource组件（做国际化功能；消息绑定，消息解析） ###

AbstractApplicationContext .initMessageSource()方法实现代码：

protected void initMessageSource() {
        //获取beanFactory
        ConfigurableListableBeanFactory beanFactory = getBeanFactory();
        //判断是否已经存在id为MESSAGE_SOURCE_BEAN_NAME的组件
        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.isDebugEnabled()) {
              logger.debug("Using MessageSource [" + this.messageSource + "]");
           }
        }
        else {
           // Use empty MessageSource to be able to accept getMessage calls.
           DelegatingMessageSource dms = new DelegatingMessageSource();
           dms.setParentMessageSource(getInternalParentMessageSource());
           this.messageSource = dms;
           beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);
           if (logger.isDebugEnabled()) {
              logger.debug("Unable to locate MessageSource with name '" + MESSAGE_SOURCE_BEAN_NAME +
                    "': using default [" + this.messageSource + "]");
           }
        }
     }

### 3.7  初始化事件派发器 ###

AbstractApplicationContext .initApplicationEventMulticaster()方法实现逻辑

protected void initApplicationEventMulticaster() {
        //获取BeanFactory
        ConfigurableListableBeanFactory beanFactory = getBeanFactory();
        //如果有配置beanName为applicationEventMulticaster的事件派发器，则将其赋给容器中的applicationEventMulticaster对象
        if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
           this.applicationEventMulticaster =
                 beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
           if (logger.isDebugEnabled()) {
              logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
           }
        }
        else {
           //不存在，则创建一个SimpleApplicationEventMulticaster事件派发器，并注册到beanfactory中
           this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
           beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
           if (logger.isDebugEnabled()) {
              logger.debug("Unable to locate ApplicationEventMulticaster with name '" +
                    APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
                    "': using default [" + this.applicationEventMulticaster + "]");
           }
        }
     }

### 3.8  注册时间监听器，将项目里面的ApplicationListener注册到容器中来 ###

registerListeners方法主要实现将事件监听器添加到IOC容器中的事件派发器中，并在最后做了一个事件发布的逻辑(如果之前的步骤有产生事件，则将earlyApplicationEvents中保存的事件逐一发布)

AbstractApplicationContext .registerListeners()方法实现逻辑：

protected void registerListeners() {
        // Register statically specified listeners first.
        for (ApplicationListener<?> listener : getApplicationListeners()) {
           getApplicationEventMulticaster().addApplicationListener(listener);
        }
     
        // Do not initialize FactoryBeans here: We need to leave all regular beans
        // uninitialized to let post-processors apply to them!
        String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
        for (String listenerBeanName : listenerBeanNames) {
           getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
        }
     
        // Publish early application events now that we finally have a multicaster...
        Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
        this.earlyApplicationEvents = null;
        if (earlyEventsToProcess != null) {
           for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
              getApplicationEventMulticaster().multicastEvent(earlyEvent);
           }
        }
     }

### 3.9  初始化所有剩下的单实例bean,单例bean在初始化容器时创建，原型bean在获取时（getbean）时创建 ###

AbstractApplicationContext.finishBeanFactoryInitialization(beanFactory);方法实现代码：

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
        //组件转换器相关
        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));
        }
     
        //aspectj相关.
        String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
        for (String weaverAwareName : weaverAwareNames) {
           getBean(weaverAwareName);
        }
     
        // Stop using the temporary ClassLoader for type matching.
        beanFactory.setTempClassLoader(null);
     
        // Allow for caching all bean definition metadata, not expecting further changes.
        beanFactory.freezeConfiguration();
     
        // 初始化后剩下的单实例bean
        beanFactory.preInstantiateSingletons();
     }

DefaultListableBeanFactory. preInstantiateSingletons()方法实现逻辑：

public void preInstantiateSingletons() throws BeansException {
        if (logger.isDebugEnabled()) {
           logger.debug("Pre-instantiating singletons in " + this);
        }
     
        // Iterate over a copy to allow for init methods which in turn register new bean definitions.
        // While this may not be part of the regular factory bootstrap, it does otherwise work fine.
     　　//容器中所有bean名称
        List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
     
        // Trigger initialization of all non-lazy singleton beans...
        for (String beanName : beanNames) {
     　　   //获取Bean的定义信息；RootBeanDefinition
           RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
     　　   //非抽象，单例，非延迟加载
           if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
     　　      //是否是FactoryBean
              if (isFactoryBean(beanName)) {
                 // 通过"&beanName"获取工厂Bean实例
                 Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
                 if (bean instanceof FactoryBean) {
                    final FactoryBean<?> factory = (FactoryBean<?>) bean;
                    boolean isEagerInit;
                    if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                       isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
                                   ((SmartFactoryBean<?>) factory)::isEagerInit,
                             getAccessControlContext());
                    }
                    else {
                       isEagerInit = (factory instanceof SmartFactoryBean &&
                             ((SmartFactoryBean<?>) factory).isEagerInit());
                    }
                    if (isEagerInit) {
                       getBean(beanName);
                    }
                 }
              }
              else {
     　　　　　　 //不是FactoryBean,则利用getBean(beanName)实例化bean 
                 getBean(beanName);
              }
           }
        }
     
        // Trigger post-initialization callback for all applicable beans...
        for (String beanName : beanNames) {
           Object singletonInstance = getSingleton(beanName);
           if (singletonInstance instanceof SmartInitializingSingleton) {
              final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
              if (System.getSecurityManager() != null) {
                 AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
                    smartSingleton.afterSingletonsInstantiated();
                    return null;
                 }, getAccessControlContext());
              }
              else {
                 smartSingleton.afterSingletonsInstantiated();
              }
           }
        }
     }

### 3.10  完成BeanFactory的初始化创建工作，IOC容器就创建完成 ###

AbstractApplicationContext.finishRefresh()实现逻辑：

protected void finishRefresh() {
        // Clear context-level resource caches (such as ASM metadata from scanning).
        clearResourceCaches();
     
        //初始化和生命周期有关的后置处理器LifecycleProcessor，默认DefaultLifecycleProcessor
        initLifecycleProcessor();
     
        // 回调生命周期处理器
        getLifecycleProcessor().onRefresh();
     
        //发布容器刷新完成事件：ContextRefreshedEvent
        publishEvent(new ContextRefreshedEvent(this));
     
        LiveBeansView.registerApplicationContext(this);
     }

以上基本分析了AnnotationConfigApplicationContext容器的初始化过程， Spring容器在启动过程中，会先保存所有注册进来的Bean的定义信息；Spring容器根据条件创建Bean实例，区分单例，还是原型，后置处理器等（后置处理器会在容器创建过程中通过getBean创建，并执行相应的逻辑）；Spring容器在创建bean实例后，会使用多种后置处理器来增加bean的功能，比如处理自动注入，AOP，异步，这种后置处理器机制也丰富了bean的功能。

原文地址

[Spring源码解析 – AnnotationConfigApplicationContext容器创建过程 - 互联网荒漠 - 博客园][Spring_ _ AnnotationConfigApplicationContext]

[Spring_ _ AnnotationConfigApplicationContext]: https://www.cnblogs.com/ashleyboy/p/9662119.html