spring IOC 源码解析二 AbstractApplicationContext源码解析

AbstractApplicationContext类在整个 Spring IOC中起着关键的作用，其中最核心的是它实现父类ConfigurableApplicationContext的refresh()方法，源码如下：

    @Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			//1、 Prepare this context for refreshing.
			prepareRefresh();

			//2、 Tell the subclass to refresh the internal bean factory.
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			//3、 Prepare the bean factory for use in this context.
			prepareBeanFactory(beanFactory);

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

				//5、 Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);

				//6、 Register bean processors that intercept bean creation.
				registerBeanPostProcessors(beanFactory);

				//7、 Initialize message source for this context.
				initMessageSource();

				//8、 Initialize event multicaster for this context.
				initApplicationEventMulticaster();

				//9、 Initialize other special beans in specific context subclasses.
				onRefresh();

				//10、 Check for listener beans and register them.
				registerListeners();

				//11、 Instantiate all remaining (non-lazy-init) singletons.
				finishBeanFactoryInitialization(beanFactory);

				//12、 Last step: publish corresponding event.
				finishRefresh();
			}

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

				//13、 Destroy already created singletons to avoid dangling resources.
				destroyBeans();

				//14、 Reset 'active' flag.
				cancelRefresh(ex);

				//15、Propagate exception to caller.
				throw ex;
			}

			finally {
				//16、 Reset common introspection caches in Spring's core, since we
				// might not ever need metadata for singleton beans anymore...
				resetCommonCaches();
			}
		}
	}