类继承图如下：
其中的父类AbstractRefreshableApplicationContext中定义了一个DefaultListableBeanFactory对象:
@Nullable
private DefaultListableBeanFactory beanFactory;AbstractApplicationContext中定义了obtainFreshBeanFactory方法
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
return getBeanFactory();
}其中调用了getBeanFactory方法。
AbstractApplicationContext的子类AbstractRefreshableApplicationContext实现getBeanFactory方法如下：
public final ConfigurableListableBeanFactory getBeanFactory() {
synchronized (this.beanFactoryMonitor) {
if (this.beanFactory == null) {
throw new IllegalStateException("BeanFactory not initialized or already closed - " +
"call 'refresh' before accessing beans via the ApplicationContext");
}
return this.beanFactory;
}
}该方法实际返回的就是DefaultListableBeanFactory对象
