理解 AbstractApplicationContext

最新推荐文章于 2022-06-29 23:37:06 发布

原创最新推荐文章于 2022-06-29 23:37:06 发布 · 1.2k 阅读

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本文详细解析了Spring容器的启动过程，包括初始化BeanFactory、预处理BeanFactory、调用BeanFactory后置处理器、注册Bean后置处理器等关键步骤，以及初始化消息源、事件广播器等内容。同时介绍了初始化bean的生命周期和重要类配置。

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启动方法

@Override
public void refresh() throws BeansException, IllegalStateException {
	synchronized (this.startupShutdownMonitor) {
		// Prepare this context for refreshing.
		//刷新上下文环境，为容器启动做环境准备，可扩展
		prepareRefresh();
		// Tell the subclass to refresh the internal bean factory.
		//初始化一个可以配置的BeanFactory，XML配置方式，会加载所有的配置文件，注解的不做任何事情
		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 the context.
			invokeBeanFactoryPostProcessors(beanFactory);

			// 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) {
			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();
		}
	}
}

初始化bean的生命周期

/**
	 * Initialize the LifecycleProcessor.
	 * Uses DefaultLifecycleProcessor if none defined in the context.
	 * @see org.springframework.context.support.DefaultLifecycleProcessor
	 */
	protected void initLifecycleProcessor() {
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (beanFactory.containsLocalBean(LIFECYCLE_PROCESSOR_BEAN_NAME)) {
			this.lifecycleProcessor =
					beanFactory.getBean(LIFECYCLE_PROCESSOR_BEAN_NAME, LifecycleProcessor.class);
			if (logger.isDebugEnabled()) {
				logger.debug("Using LifecycleProcessor [" + this.lifecycleProcessor + "]");
			}
		}
		else {
			DefaultLifecycleProcessor defaultProcessor = new DefaultLifecycleProcessor();
			defaultProcessor.setBeanFactory(beanFactory);
			this.lifecycleProcessor = defaultProcessor;
			beanFactory.registerSingleton(LIFECYCLE_PROCESSOR_BEAN_NAME, this.lifecycleProcessor);
			if (logger.isDebugEnabled()) {
				logger.debug("Unable to locate LifecycleProcessor with name '" +
						LIFECYCLE_PROCESSOR_BEAN_NAME +
						"': using default [" + this.lifecycleProcessor + "]");
			}
		}
	}