Spring源码阅读——ApplicationContext た 入场券 2022-05-18 22:55 176阅读 0赞 Spring中提供了一个接口ApplicationContext,用于扩展BeanFactory中现有的功能。它提供了更多的功能。现在我们来看下它的实现: public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) throws BeansException { super(parent); setConfigLocations(configLocations); if (refresh) { refresh(); } } 其中refresh();方法几乎包含了所有的功能,逻辑非常清晰 public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // Prepare this context for refreshing. //环境准备,比如系统属性、环境变量的初始化及验证 prepareRefresh(); // Tell the subclass to refresh the internal bean factory. //初始化BeanFactory ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. //对BeanFactory进行各种功能填充 prepareBeanFactory(beanFactory); try { // Allows post-processing of the bean factory in context subclasses. //子类覆盖方法做额外处理 postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context. //激活各种BeanFactory处理器 invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation. //注册拦截Bean创建的Bean处理器,这里只是注册,真正地调用在getBean的时候,比如配置文件通过${}读取等 registerBeanPostProcessors(beanFactory); // Initialize message source for this context. //为上下文初始化Message源,(比如国际化处理) initMessageSource(); // Initialize event multicaster for this context. //初始化应用消息广播,并放入 applicationEventMulticaster bean中 initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses. //留给子类来初始化其它的bean onRefresh(); // Check for listener beans and register them. //在所有注册的bean中查找Listener bean,注册到消息广播器中 registerListeners(); // Instantiate all remaining (non-lazy-init) singletons. //初始化剩下的单实例 finishBeanFactoryInitialization(beanFactory); //完成刷新过程,通知生命周期护处理器lifecycleProcessor刷新过程,同时发出ContextRefreshEvent通知别人(LifecycleProcessor 用来与所有声明的bean的周期做状态更新) // Last step: publish corresponding event. 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(); } } }
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