Spring AbstractXmlApplicationContext

@Override
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
   // 创建 读取 xml bean定义的类
   // Create a new XmlBeanDefinitionReader for the given BeanFactory.
   XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

   // Configure the bean definition reader with this context's
   // resource loading environment.
   // 设置环境
   beanDefinitionReader.setEnvironment(this.getEnvironment());
   // 设置资源加载器
   beanDefinitionReader.setResourceLoader(this);
   // 资源解析器
   beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

   // Allow a subclass to provide custom initialization of the reader,
   // then proceed with actually loading the bean definitions.
   // 初始化 bean定义阅读器
   initBeanDefinitionReader(beanDefinitionReader);
   // 加载 bean 定义
   loadBeanDefinitions(beanDefinitionReader);
}