Ioc容器實際上就是Context組件結合其他兩個組件共同構建了一個Bean關系網，如何構建這個關系網？構建的入口就在AbstractApplicationContext類的refresh方法中。這個方法的代碼如下：

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;    
 
        }  
 
    }  
 
}  
 

這個方法就是構建整個Ioc容器過程的完整的代碼，了解了里面的每一行代碼基本上就了解大部分Spring的原理和功能了。

這段代碼主要包含這樣幾個步驟：

• 構建BeanFactory，以便于產生所需的“演員”
• 注冊可能感興趣的事件
• 創建Bean實例對象
• 觸發被監聽的事件

下面就結合代碼分析這幾個過程。

第二三句就是在創建和配置BeanFactory。這里是refresh也就是刷新配置，前面介紹了Context有可更新的子類，這里正是實現這個功能，當BeanFactory已存在是就更新，如果沒有就新創建。