beanFactory的继承关系如下图所示：
(图片来源：http://www.myexception.cn/software-architecture-design/925888.html)
在上节beanFactory的进化史，我们就讲到了上图的左边部分，这次我们来分析一下图的右边部分。AliasRegistry 是一个用于别名管理的通用接口，BeanDefinitionRegistry继承了该接口。
SimpleAliasRegistry作为一个基类，实现了AliasRegistry接口。
SingletonBeanRegistry是spring 提供的一个共享bean的注册接口。实现该接口可以方便对单例进行管理。
public interface SingletonBeanRegistry { /** * Register the given existing object as singleton in the bean registry, * under the given bean name. * <p>The given instance is supposed to be fully initialized; the registry * will not perform any initialization callbacks (in particular, it won't * call InitializingBean's {@code afterPropertiesSet} method). * The given instance will not receive any destruction callbacks * (like DisposableBean's {@code destroy} method) either. * <p>When running within a full BeanFactory: <b>Register a bean definition * instead of an existing instance if your bean is supposed to receive * initialization and/or destruction callbacks.</b> * <p>Typically invoked during registry configuration, but can also be used * for runtime registration of singletons. As a consequence, a registry * implementation should synchronize singleton access; it will have to do * this anyway if it supports a BeanFactory's lazy initialization of singletons. * @param beanName the name of the bean * @param singletonObject the existing singleton object * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet * @see org.springframework.beans.factory.DisposableBean#destroy * @see org.springframework.beans.factory.support.BeanDefinitionRegistry#registerBeanDefinition */ void registerSingleton(String beanName, Object singletonObject); /** * Return the (raw) singleton object registered under the given name. * <p>Only checks already instantiated singletons; does not return an Object * for singleton bean definitions which have not been instantiated yet. * <p>The main purpose of this method is to access manually registered singletons * (see {@link #registerSingleton}). Can also be used to access a singleton * defined by a bean definition that already been created, in a raw fashion. * <p><b>NOTE:</b> This lookup method is not aware of FactoryBean prefixes or aliases. * You need to resolve the canonical bean name first before obtaining the singleton instance. * @param beanName the name of the bean to look for * @return the registered singleton object, or {@code null} if none found * @see ConfigurableListableBeanFactory#getBeanDefinition */ Object getSingleton(String beanName); /** * Check if this registry contains a singleton instance with the given name. * <p>Only checks already instantiated singletons; does not return {@code true} * for singleton bean definitions which have not been instantiated yet. * <p>The main purpose of this method is to check manually registered singletons * (see {@link #registerSingleton}). Can also be used to check whether a * singleton defined by a bean definition has already been created. * <p>To check whether a bean factory contains a bean definition with a given name, * use ListableBeanFactory's {@code containsBeanDefinition}. Calling both * {@code containsBeanDefinition} and {@code containsSingleton} answers * whether a specific bean factory contains a local bean instance with the given name. * <p>Use BeanFactory's {@code containsBean} for general checks whether the * factory knows about a bean with a given name (whether manually registered singleton * instance or created by bean definition), also checking ancestor factories. * <p><b>NOTE:</b> This lookup method is not aware of FactoryBean prefixes or aliases. * You need to resolve the canonical bean name first before checking the singleton status. * @param beanName the name of the bean to look for * @return if this bean factory contains a singleton instance with the given name * @see #registerSingleton * @see org.springframework.beans.factory.ListableBeanFactory#containsBeanDefinition * @see org.springframework.beans.factory.BeanFactory#containsBean */ boolean containsSingleton(String beanName); /** * Return the names of singleton beans registered in this registry. * <p>Only checks already instantiated singletons; does not return names * for singleton bean definitions which have not been instantiated yet. * <p>The main purpose of this method is to check manually registered singletons * (see {@link #registerSingleton}). Can also be used to check which singletons * defined by a bean definition have already been created. * @return the list of names as a String array (never {@code null}) * @see #registerSingleton * @see org.springframework.beans.factory.support.BeanDefinitionRegistry#getBeanDefinitionNames * @see org.springframework.beans.factory.ListableBeanFactory#getBeanDefinitionNames */ String[] getSingletonNames(); /** * Return the number of singleton beans registered in this registry. * <p>Only checks already instantiated singletons; does not count * singleton bean definitions which have not been instantiated yet. * <p>The main purpose of this method is to check manually registered singletons * (see {@link #registerSingleton}). Can also be used to count the number of * singletons defined by a bean definition that have already been created. * @return the number of singleton beans * @see #registerSingleton * @see org.springframework.beans.factory.support.BeanDefinitionRegistry#getBeanDefinitionCount * @see org.springframework.beans.factory.ListableBeanFactory#getBeanDefinitionCount */ int getSingletonCount(); }
注册接口的默认实现为：DefaultSingletonBeanRegistry，主要作用是提供能被所有调用者共享bean的注册，调用者可用通过bean 名称获取到该bean的实例。同时该类也提供了对注册bean的销毁方法。
DefaultSingletonBeanRegistry也实现了AliasRegistry接口，增加了对别名的管理。
FactoryBeanRegistrySupport 集成了DefaultSingletonBeanRegistry对bean的单例bean的管理功能，是一个基类，用来处理FactoryBean实例的单例bean的注册。
我们重点介绍来研究一下AbstractBeanFactory的代码：
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory { // to do more }
从继承关系上来讲，AbstractBeanFactory具备了ConfigurableBeanFactory 的完整功能，