Spring-IoC容器初始化流程源码分析

ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:spring.xml</param-value>
</context-param>
<listener>
    <listener-class>
        org.springframework.web.context.ContextLoaderListener
    </listener-class>
</listener>

public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            // STEP 1： 刷新预处理
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            // STEP 2：
            //      a） 创建IoC容器（DefaultListableBeanFactory）
            //      b） 加载解析XML文件（最终存储到Document对象中）
            //      c） 读取Document对象，并完成BeanDefinition的加载和注册工作
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            // STEP 3： 对IoC容器进行一些预处理（设置一些公共属性）
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                // STEP 4： 
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                // STEP 5： 调用BeanFactoryPostProcessor后置处理器对BeanDefinition处理
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                // STEP 6： 注册BeanPostProcessor后置处理器
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                // STEP 7： 初始化一些消息源（比如处理国际化的i18n等消息源）
                initMessageSource();

                // Initialize event multicaster for this context.
                // STEP 8： 初始化应用事件广播器
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                // STEP 9： 初始化一些特殊的bean
                onRefresh();

                // Check for listener beans and register them.
                // STEP 10： 注册一些监听器
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                // STEP 11： 实例化剩余的单例bean（非懒加载方式）
                // 注意事项：Bean的IoC、DI和AOP都是发生在此步骤
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                // STEP 12： 完成刷新时，需要发布对应的事件
                finishRefresh();
            }

            catch (BeansException ex) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Exception encountered during context initialization - " +
                            "cancelling refresh attempt: " + ex);
                }

                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset 'active' flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }

            finally {
                // Reset common introspection caches in Spring's core, since we
                // might not ever need metadata for singleton beans anymore...
                resetCommonCaches();
            }
        }
    }