Mr. Cappuccino的第63杯咖啡——Spring之AnnotationConfigApplicationContext源码分析

源码分析

以上一篇文章《Spring之Bean的生命周期》的代码进行源码分析

AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringConfig02.class);
LifeCycleBean lifeCycleBean = applicationContext.getBean("lifeCycleBean", LifeCycleBean.class);
System.out.println("-----------------------------------");
System.out.println("LifeCycleBean " + lifeCycleBean);
System.out.println("-----------------------------------");
applicationContext.close();

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new AnnotationConfigApplicationContext(SpringConfig02.class)

AnnotationConfigApplicationContext.java

AbstractApplicationContext.java

@Override
public void refresh() throws BeansException, IllegalStateException {
    
    
	synchronized (this.startupShutdownMonitor) {
    
    
		// Prepare this context for refreshing.
		// 容器刷新前的准备工作，例如对系统属性、环境变量进行准备及验证
		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进行属性填充及功能填充，例如添加某些BeanPostProcessor以实现某些功能（ApplicationContextAwareProcessor）
		prepareBeanFactory(beanFactory);

		try {
    
    
			// Allows post-processing of the bean factory in context subclasses.
			// 空方法，用于子类实现扩展功能
			postProcessBeanFactory(beanFactory);

			// Invoke factory processors registered as beans in the context.
			// 执行BeanFactoryPostProcessor，例如ConfigurationClassPostProcessor、EventListenerMethodProcessor以及某些自定义的BeanFactoryPostProcessor
			// ConfigurationClassPostProcessor用于处理配置类，会将配置类中需要注册的Bean对象的元数据解析并存入beanDefinitionMap集合中
			invokeBeanFactoryPostProcessors(beanFactory);

			// Register bean processors that intercept bean creation.
			// 注册BeanPostProcessor，例如AutowiredAnnotationBeanPostProcessor、CommonAnnotationBeanPostProcessor以及某些自定义的BeanPostProcessor
			registerBeanPostProcessors(beanFactory);

			// Initialize message source for this context.
			// 初始化消息资源，国际化处理
			initMessageSource();

			// Initialize event multicaster for this context.
			// 初始化消息多播器
			initApplicationEventMulticaster();

			// Initialize other special beans in specific context subclasses.
			// 空方法，用于子类实现扩展功能
			onRefresh();

			// Check for listener beans and register them.
			// 注册所有的ApplicationListener到消息多播器
			registerListeners();

			// Instantiate all remaining (non-lazy-init) singletons.
			// 实例化、初始化剩下的非懒加载的单例对象
			finishBeanFactoryInitialization(beanFactory);

			// Last step: publish corresponding event.
			// 完成刷新动作，启动LifecycleProcessor，发布ContextRefreshedEvent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.
			// 销毁已创建的单例对象
			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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BeanFactory中两个重要的对象

DefaultListableBeanFactory.java

/** Map of bean definition objects, keyed by bean name. */
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);

DefaultSingletonBeanRegistry.java

/** Cache of singleton objects: bean name to bean instance. */
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);

Debug源码分析

register(componentClasses)：注册指定的配置类SpringConfig02到beanDefinitionMap集合中

invokeBeanFactoryPostProcessors(beanFactory)：创建BeanFactoryPostProcessor接口相关实现类的实例对象并存入singletonObjects集合中；执行BeanFactoryPostProcessor接口相关实现类的方法，通过ConfigurationClassPostProcessor处理配置类中需要注册的bean对象，并将bean对象注册到beanDefinitionMap集合中。

registerBeanPostProcessors(beanFactory)：注册BeanPostProcessor接口相关实现类，创建BeanPostProcessor接口相关实现类的实例对象并存入singletonObjects集合中

finishBeanFactoryInitialization(beanFactory)：实例化、初始化剩下的非懒加载的单例对象并存入singletonObjects集合中

beanFactory.preInstantiateSingletons()：提前加载单例对象

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