第七章 Spring Bean Definition 注册

BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry())

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

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

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

private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);

在这个容器中 key ： Bean Name ，value：Bean Definition 。

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

public void validate() throws BeanDefinitionValidationException {
   // 是否存在重写方法, factory_method_name 是否为空
   if (hasMethodOverrides() && getFactoryMethodName() != null) {
      throw new BeanDefinitionValidationException(
            "Cannot combine factory method with container-generated method overrides: " +
                  "the factory method must create the concrete bean instance.");
   }
   //  bean class 是否等于 Class
   if (hasBeanClass()) {
      // 方法重写+验证
      prepareMethodOverrides();
   }
}

@Override
public void validate() throws BeanDefinitionValidationException {
   super.validate();
   if (this.parentName == null) {
      throw new BeanDefinitionValidationException("'parentName' must be set in ChildBeanDefinition");
   }
}

// 第二部分 beanName 存在 BeanDefinition 的情况
// 从 map 中根据 beanName 获取 beanDefinition
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
   // bean name 是否允许重复注册
   if (!isAllowBeanDefinitionOverriding()) {
      throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
   }
   // role 值比较
   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 + "]");
      }
   }
   // map 中存储的 beanDefinition 是否和参数相同
   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 + "]");
      }
   }
   // 设置 beanName 和 beanDefinition 关系
   this.beanDefinitionMap.put(beanName, beanDefinition);
}

if (!isAllowBeanDefinitionOverriding()) {
   throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}

else {
   // 检查 bean 是否已经开始创建
   if (hasBeanCreationStarted()) {
      // Cannot modify startup-time collection elements anymore (for stable iteration)
      synchronized (this.beanDefinitionMap) {
         // 设置 beanName 和 beanDefinition 关系
         this.beanDefinitionMap.put(beanName, beanDefinition);
         // bean definition 的名称列表
         List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
         // 加入内存数据
         updatedDefinitions.addAll(this.beanDefinitionNames);
         // 加入当前的 beanName
         updatedDefinitions.add(beanName);
         // 对象替换
         this.beanDefinitionNames = updatedDefinitions;
         // 移除当前的beanName
         removeManualSingletonName(beanName);
      }
   }
   else {
      // Still in startup registration phase
      // 设置容器数据
      this.beanDefinitionMap.put(beanName, beanDefinition);
      this.beanDefinitionNames.add(beanName);
      // 移除当前的beanName
      removeManualSingletonName(beanName);
   }
   this.frozenBeanDefinitionNames = null;
}

protected boolean hasBeanCreationStarted() {
   return !this.alreadyCreated.isEmpty();
}

private void removeManualSingletonName(String beanName) {
   updateManualSingletonNames(set -> set.remove(beanName), set -> set.contains(beanName));
}

private void updateManualSingletonNames(Consumer<Set<String>> action, Predicate<Set<String>> condition) {
   if (hasBeanCreationStarted()) {
      // Cannot modify startup-time collection elements anymore (for stable iteration)
      synchronized (this.beanDefinitionMap) {
         // 输入的 beanName 是否在 manualSingletonNames 存在
         if (condition.test(this.manualSingletonNames)) {
            // 数据重写
            Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
            // 删除 beanName
            action.accept(updatedSingletons);
            // 数据重写
            this.manualSingletonNames = updatedSingletons;
         }
      }
   }
   else {
      // Still in startup registration phase
      // 输入的 beanName 是否在 manualSingletonNames 存在
      if (condition.test(this.manualSingletonNames)) {
         // 删除 beanName
         action.accept(this.manualSingletonNames);
      }
   }
}

if (existingDefinition != null || containsSingleton(beanName)) {
   // 刷新bean definition
   resetBeanDefinition(beanName);
}

// 将 父 BeanDefinition 对象拷贝
mbd = new RootBeanDefinition(pbd);
// 覆盖 beanDefinition
mbd.overrideFrom(bd);

public void resetBeanDefinition(String beanName) {
   this.lookupMethodsChecked.remove(beanName);
   this.injectionMetadataCache.remove(beanName);
}

protected void resetBeanDefinition(String beanName) {
   // Remove the merged bean definition for the given bean, if already created.
   // 清空合并的BeanDefinition
   clearMergedBeanDefinition(beanName);

   // Remove corresponding bean from singleton cache, if any. Shouldn't usually
   // be necessary, rather just meant for overriding a context's default beans
   // (e.g. the default StaticMessageSource in a StaticApplicationContext).
   // 摧毁单例bean
   destroySingleton(beanName);

   // Notify all post-processors that the specified bean definition has been reset.
   // 后置处理器执行 resetBeanDefinition 方法
   for (BeanPostProcessor processor : getBeanPostProcessors()) {
      if (processor instanceof MergedBeanDefinitionPostProcessor) {
         // 执行后置方法的 resetBeanDefinition
         ((MergedBeanDefinitionPostProcessor) processor).resetBeanDefinition(beanName);
      }
   }

   // Reset all bean definitions that have the given bean as parent (recursively).
   // 处理其他的 bean name
   for (String bdName : this.beanDefinitionNames) {
      if (!beanName.equals(bdName)) {
         BeanDefinition bd = this.beanDefinitionMap.get(bdName);
         // Ensure bd is non-null due to potential concurrent modification
         // of the beanDefinitionMap.
         // beanName 等于 父名称
         if (bd != null && beanName.equals(bd.getParentName())) {
            // 递归刷新 beanName 对应的 beanDefinition
            resetBeanDefinition(bdName);
         }
      }
   }
}

private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);

@Override
public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
   BeanDefinition bd = this.beanDefinitionMap.get(beanName);
   if (bd == null) {
      if (logger.isTraceEnabled()) {
         logger.trace("No bean named '" + beanName + "' found in " + this);
      }
      throw new NoSuchBeanDefinitionException(beanName);
   }
   return bd;
}