New ClassPathXmlApplicationContext经历了哪些事情

ApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:NonOsgiConsumerSample.xml");

 这是一段很简单的ApplicationContext初始化的代码，但是在这段代码的背后，springframework又为我们做了哪些事情，使得我们能够从容器中方便的获取我们想要的bean？

跟踪代码我们发现在创建一个ClassPathXmlApplicationContext的过程中，它主要经历了以下几个步骤

ClassPathXmlApplicationContext(String configLocation) ----> 
ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) ----->
AbstractXmlApplicationContext(ApplicationContext parent) ---->
AbstractRefreshableConfigApplicationContext(ApplicationContext parent)---->
AbstractRefreshableApplicationContext(ApplicationContext parent) ->
AbstractApplicationContext(ApplicationContext parent)
//最终在AbstractApplicationContext.refresh()完成bean初始化
AbstractApplicationContext.refresh()

AbstractXmlApplicationContext实现了loadBeanDefinitions() ，它的子类只需实现getConfigResources()

 

	protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws IOException {
		// Create a new XmlBeanDefinitionReader for the given BeanFactory.
		XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

		// Configure the bean definition reader with this context's
		// resource loading environment.
		beanDefinitionReader.setResourceLoader(this);
		beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

		// Allow a subclass to provide custom initialization of the reader,
		// then proceed with actually loading the bean definitions.
		initBeanDefinitionReader(beanDefinitionReader);
		loadBeanDefinitions(beanDefinitionReader);
	}

 AbstractRefreshableApplicationContext支持多重刷新，每次在内部会创建一个新的bean factory实例，子类只需实现loadBeanDefinitions()

//AbstractRefreshableApplicationContext关键代码	
protected final void refreshBeanFactory() throws BeansException {
		if (hasBeanFactory()) {
			destroyBeans();
			closeBeanFactory();
		}
		try {
			DefaultListableBeanFactory beanFactory = createBeanFactory();
			customizeBeanFactory(beanFactory);
			loadBeanDefinitions(beanFactory);
			synchronized (this.beanFactoryMonitor) {
				this.beanFactory = beanFactory;
			}
		}
		catch (IOException ex) {
			throw new ApplicationContextException(
					"I/O error parsing XML document for application context [" + getDisplayName() + "]", ex);
		}
	}

 

AbstractApplicationContext.refresh()

public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			prepareRefresh();    //无需关注

			// Tell the subclass to refresh the internal bean factory.调用了refreshBeanFactory()
			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);  //无需关注，在webapplicationcontext可能用到

				// Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);
                                                                //实例化和调用所有实现了BeanFactoryPostProcessor的bean
				// Register bean processors that intercept bean creation.
				registerBeanPostProcessors(beanFactory);

				// Initialize message source for this context.
				initMessageSource();

				// Initialize event multicaster for this context.
				initApplicationEventMulticaster();

				// Initialize other special beans in specific context 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 dangling resources.
				beanFactory.destroySingletons();

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

				// Propagate exception to caller.
				throw ex;
			}
		}
	}