Spring源码解析 – AnnotationConfigApplicationContext容器创建过程

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. 注册事件监听器，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