Ioc容器實(shí)際上就是Context組件結(jié)合其他兩個(gè)組件共同構(gòu)建了一個(gè)Bean關(guān)系網(wǎng)，如何構(gòu)建這個(gè)關(guān)系網(wǎng)？構(gòu)建的入口就在AbstractApplicationContext類的refresh方法中。這個(gè)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(gè)方法就是構(gòu)建整個(gè)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(gè)步驟：

• 構(gòu)建BeanFactory，以便于產(chǎn)生所需的“演員”
• 注冊可能感興趣的事件
• 創(chuàng)建Bean實(shí)例對象
• 觸發(fā)被監(jiān)聽的事件

下面就結(jié)合代碼分析這幾個(gè)過程。

第二三句就是在創(chuàng)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(shí)現(xiàn)這個(gè)功能，當(dāng)BeanFactory已存在是就更新，如果沒有就新創(chuàng)建。