Spring源码解析-IOC控制反转（三）根据BeanDefinitionHolder，将信息保存到注册中心beanDefinitionMap

接上篇《Spring源码解析-IOC控制反转（二）操作dom树，取得标签数据》
上篇说到从dom树中取得Bean标签数据生成BeanDefinitionHolder，开始注册Bean

// BeanDefinitionReaderUtils 160
public static void registerBeanDefinition(
      BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
      throws BeanDefinitionStoreException {

   // Register bean definition under primary name.
   String beanName = definitionHolder.getBeanName();
   registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

   // Register aliases for bean name, if any.
   String[] aliases = definitionHolder.getAliases();
   if (aliases != null) {
      for (String alias : aliases) {
         registry.registerAlias(beanName, alias);
      }
   }
}

根据beanName注册这个Bean，如果有别名的话，也要根据别名注册bean。

// DefaultListableBeanFactory 908
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
      throws BeanDefinitionStoreException {

   Assert.hasText(beanName, "Bean name must not be empty");
   Assert.notNull(beanDefinition, "BeanDefinition must not be null");

   
   if (beanDefinition instanceof AbstractBeanDefinition) {
      try {
      // 校验Bean
         ((AbstractBeanDefinition) beanDefinition).validate();
      }
      catch (BeanDefinitionValidationException ex) {
         throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
               "Validation of bean definition failed", ex);
      }
   }

   BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
   if (existingDefinition != null) {
      if (!isAllowBeanDefinitionOverriding()) {
         throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
      }
      else if (existingDefinition.getRole() < beanDefinition.getRole()) {
         // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
         if (logger.isInfoEnabled()) {
            logger.info("Overriding user-defined bean definition for bean '" + beanName +
                  "' with a framework-generated bean definition: replacing [" +
                  existingDefinition + "] with [" + beanDefinition + "]");
         }
      }
      else if (!beanDefinition.equals(existingDefinition)) {
         if (logger.isDebugEnabled()) {
            logger.debug("Overriding bean definition for bean '" + beanName +
                  "' with a different definition: replacing [" + existingDefinition +
                  "] with [" + beanDefinition + "]");
         }
      }
      else {
         if (logger.isTraceEnabled()) {
            logger.trace("Overriding bean definition for bean '" + beanName +
                  "' with an equivalent definition: replacing [" + existingDefinition +
                  "] with [" + beanDefinition + "]");
         }
      }
      this.beanDefinitionMap.put(beanName, beanDefinition);
   }
   else {
      if (hasBeanCreationStarted()) {
         // Cannot modify startup-time collection elements anymore (for stable iteration)
         synchronized (this.beanDefinitionMap) {
            this.beanDefinitionMap.put(beanName, beanDefinition);
            List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
            updatedDefinitions.addAll(this.beanDefinitionNames);
            updatedDefinitions.add(beanName);
            this.beanDefinitionNames = updatedDefinitions;
            removeManualSingletonName(beanName);
         }
      }
      else {
         // Still in startup registration phase
         this.beanDefinitionMap.put(beanName, beanDefinition);
         this.beanDefinitionNames.add(beanName);
         removeManualSingletonName(beanName);
      }
      this.frozenBeanDefinitionNames = null;
   }

   if (existingDefinition != null || containsSingleton(beanName)) {
      resetBeanDefinition(beanName);
   }
}

将所有的beanName和beanDefinition绑定，放入beanDefinitionMap中，一一对应.
beanDefinitionMap是ConcurrentHashMap类的实例。线程安全且key和value都不能为空，并且key唯一。这也就是之前为什么说beanName同一个文件不允许重复，不同文件会覆盖。

// ReaderContext 164
public void fireComponentRegistered(ComponentDefinition componentDefinition) {
   this.eventListener.componentRegistered(componentDefinition);
}

调用ReaderEventListener 监听器的组件注册事件，将发送到注册中心完成注册。