/**
 * The root interface for accessing a Spring bean container.
 * 根接口,整个访问容器的入口
 * <p>This is the basic client view of a bean container;
 * further interfaces such as {@link ListableBeanFactory} and
 * {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}
 * are available for specific purposes.
 * <p>This interface is implemented by objects that hold a number of bean definitions,
 * 这个接口是一个实现,保存很多的BeanDefinition信息,都有一个唯一的名字
 * each uniquely identified by a String name. Depending on the bean definition,
 * the factory will return either an independent instance of a contained object
 * (the Prototype design pattern), or a single shared instance (a superior
 * 这个工厂将会返回独立的实例或者返回一个共享的实例 (原型模式、单例模式)
 * alternative to the Singleton design pattern, in which the instance is a
 * singleton in the scope of the factory). 
 **/

  <T> T getBean(Class<T> requiredType) throws BeansException;