Spring-IOC从ApplicationContext角度看bean的加载流程【二】obtainFreshBeanFactory

obtainFreshBeanFactory方法的作用是告诉子类刷新内部bean工厂。

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
        //刷新bean工厂，这里使用了子类AbstractRefreshableApplicationContext中的实现
        refreshBeanFactory();
        //获取bean工厂
        return getBeanFactory();
    }

这里refreshBeanFactory()方法由子类AbstractRefreshableApplicationContext实现：

@Override
protected final void refreshBeanFactory() throws BeansException {
    //如果已经持有一个BeanFactory
    if (hasBeanFactory()) {
        //用于销毁此上下文管理的所有bean
        destroyBeans();
        //关闭持有的BeanFactory
        closeBeanFactory();
    }
    try {
        //新建一个 DefaultListableBeanFactory
        DefaultListableBeanFactory beanFactory = createBeanFactory();
        beanFactory.setSerializationId(getId());
        // 自定义此上下文使用的内部bean工厂。
        // allowBeanDefinitionOverriding
        // allowCircularReferences
        customizeBeanFactory(beanFactory);
        //加载BeanDefinitions
        loadBeanDefinitions(beanFactory);
        synchronized (this.beanFactoryMonitor) {
            this.beanFactory = beanFactory;
        }
    } catch (IOException ex) {
        throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    }
}

核心方法loadBeanDefinitions，从配置文件中加载bean的定义，看AbstractXmlApplicationContext中的实现。

//通过XmlBeanDefinitionReader加载bean定义。
	@Override
	protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
		// 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.
		beanDefinitionReader.setEnvironment(this.getEnvironment());
		beanDefinitionReader.setResourceLoader(this);
		beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

		// Allow a subclass to provide custom initialization of the reader,
		// then proceed with actually loading the bean definitions.
		initBeanDefinitionReader(beanDefinitionReader);
		loadBeanDefinitions(beanDefinitionReader);
	}