Ioc容器实际上就是Context组件结合其他两个组件共同构建了一个Bean关系网，如何构建这个关系网？构建的入口就在AbstractApplicationContext类的refresh方法中。这个方法的代码如下：

public void refresh() throws BeansException, IllegalStateException {    
 
    synchronized (this.startupShutdownMonitor) {    
 
        // Prepare this context for refreshing.    
 
        prepareRefresh();    
 
        // Tell the subclass to refresh the internal bean factory.    
 
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();    
 
        // Prepare the bean factory for use in this context.    
 
        prepareBeanFactory(beanFactory);    
 
        try {  
 
            // Allows post-  processing of the bean factory in context subclasses.  
 
            postProcessBeanFactory(beanFactory);  
 
            // Invoke factory processors registered as beans in&  nbsp;the context.  
 
            invokeBeanFactoryPostProcessors(beanFactory);    
 
            // Register bean processors that intercept bean crea  tion.  
 
            registerBeanPostProcessors  (beanFactory);  
 
            // Initialize message source for this context.    
 
            initMessageSource();    
 
            // Initialize event multicaster for this context.    
 
            initApplicationEventMulticaster();    
 
            // Initialize other special beans in specific contex  t subclasses.  
 
            onRefresh();    
 
            // Check for listener beans and register them.    
 
            registerListeners();    
 
            // Instantiate all remaining (non-lazy-init) singletons.    
 
            finishBeanFactoryInitialization  (beanFactory);  
 
            // Last step: publish corresponding event.    
 
            finishRefresh();    
 
        }  
 
        catch (BeansException ex) {  
 
            // Destroy already created singletons to avoid dangl  ing resources.  
 
            destroyBeans();    
 
            // Reset 'active' flag.    
 
            cancelRefresh(ex);    
 
            // Propagate exception to caller.    
 
            throw ex;    
 
        }  
 
    }  
 
}  
 

这个方法就是构建整个Ioc容器过程的完整的代码，了解了里面的每一行代码基本上就了解大部分Spring的原理和功能了。

这段代码主要包含这样几个步骤：

• 构建BeanFactory，以便于产生所需的“演员”
• 注册可能感兴趣的事件
• 创建Bean实例对象
• 触发被监听的事件

下面就结合代码分析这几个过程。

第二三句就是在创建和配置BeanFactory。这里是refresh也就是刷新配置，前面介绍了Context有可更新的子类，这里正是实现这个功能，当BeanFactory已存在是就更新，如果没有就新创建。