Spring IOC学习（6）——DefaultListableBeanFactory

目录

 

简介

项目启动后容器如何初始化所有单例对象

BeanFactory和ApplicationContext的关系

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简介

DefaultListableBeanFactory已经是一个成熟的容器了，是Spring的默认BeanFactory；
实现了BeanDefinitionRegistry接口，可通过读取配置文件等方式，预先注册所有bean定义；
bean定义：描述bean的作用范围、ROLE等级、是否懒加载、depends-on等信息；这个概念在AbstractBeanFactory才出现，在FactoryBeanRegistrySupport之前都没有

/**
 * 注册bean定义
 */
 @Override
 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 {
    ((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) {
   //已存在同名的bean定义
   if (!isAllowBeanDefinitionOverriding()) {
    //不允许覆盖则抛异常
    throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
      "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
      "': There is already [" + existingDefinition + "] bound.");
   }
   else if (existingDefinition.getRole() < beanDefinition.getRole()) {
    // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
    // 等级更高的bean定义将被覆盖
    if (logger.isWarnEnabled()) {
     logger.warn("Overriding user-defined bean definition for bean '" + beanName +
       "' with a framework-generated bean definition: replacing [" +
       existingDefinition + "] with [" + beanDefinition + "]");
    }
   }
   else if (!beanDefinition.equals(existingDefinition)) {
    //覆盖前打个日志
    if (logger.isInfoEnabled()) {
     logger.info("Overriding bean definition for bean '" + beanName +
       "' with a different definition: replacing [" + existingDefinition +
       "] with [" + beanDefinition + "]");
    }
   }
   else {
    if (logger.isDebugEnabled()) {
     logger.debug("Overriding bean definition for bean '" + beanName +
       "' with an equivalent definition: replacing [" + existingDefinition +
       "] with [" + beanDefinition + "]");
    }
   }
   //注册
   this.beanDefinitionMap.put(beanName, beanDefinition);
  }

  else {
   if (hasBeanCreationStarted()) {
    //容器已经进入创建bean的阶段，要做同步操作
    // Cannot modify startup-time collect