Spring源码深度解析之AnnotationConfigApplicationContext概述

2022-06-15 11:38:29

Spring的配置由基于XML，逐渐演变为基于注解，常用的应用程序上下文也由ClassPathXmlApplicationContext转为AnnotationConfigApplicationContext但基本流程都是一样的。

AnnotationConfigApplicationContext代码如下所示

publicAnnotationConfigApplicationContext(Class<?>... annotatedClasses){//这里由于他有父类，故而会先调用父类的构造方法，然后才会调用自己的构造方法//在自己构造方法中初始一个读取器和扫描器this();register(annotatedClasses);refresh();}

AnnotationConfigApplicationContext在实例化的时候会先调用父类的构造方法初始化BeanFactory，这个类包含很多重要的容器比如beanDefinitionMap等等

publicGenericApplicationContext(){//这个类包含很多重要的容器比如beanDefinitionMap等等this.beanFactory=newDefaultListableBeanFactory();}

this()方法

在this()方法中主要初始化一个读取器和一个扫描器，扫描器的的作用主要提给程序员程序员使用，在spring进行扫描的时候会再实例化一个扫描器。这里最重要是是AnnotatedBeanDefinitionReader

publicAnnotationConfigApplicationContext(){this.reader=newAnnotatedBeanDefinitionReader(this);/**
		 * 可以用来扫描宝或者类，继而转换成bd
		 * 但实际上我们扫描包不是scanner这个对象，是spring自己new的一个ClassPathBeanDefinitionScanner
		 * 这里的scanner仅仅是为了程序员能够在外部调用AnnotationConfigApplicationContext对象scan方法
		 */this.scanner=newClassPathBeanDefinitionScanner(this);}

AnnotatedBeanDefinitionReader实例化的时候会调用registerAnnotationConfigProcessors方法，在beanDefinitionMap放入几个非常重要的的类，这几个类贯整个Spring容器的生命周期

publicstatic Set<BeanDefinitionHolder>registerAnnotationConfigProcessors(
			BeanDefinitionRegistry registry,@Nullable Object source){......删除部分代码
		Set<BeanDefinitionHolder> beanDefs=newLinkedHashSet<>(8);if(!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)){
			RootBeanDefinition def=newRootBeanDefinition(ConfigurationClassPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));}if(!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)){
			RootBeanDefinition def=newRootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));}// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.if(jsr250Present&&!registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)){
			RootBeanDefinition def=newRootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));}// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.if(jpaPresent&&!registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)){
			RootBeanDefinition def=newRootBeanDefinition();try{
				def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
						AnnotationConfigUtils.class.getClassLoader()));}catch(ClassNotFoundException ex){thrownewIllegalStateException("Cannot load optional framework class: "+ PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);}
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));}if(!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)){
			RootBeanDefinition def=newRootBeanDefinition(EventListenerMethodProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));}if(!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)){
			RootBeanDefinition def=newRootBeanDefinition(DefaultEventListenerFactory.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));}return beanDefs;}

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register(annotatedClasses)方法

register(annotatedClasses)最终会调用registerBeanDefinition向beanDefinitionMap注册一个配置类，它的beanDefinition是AnnotatedGenericBeanDefinition。

private<T>voiddoRegisterBean(Class<T> beanClass,@Nullable String name,@Nullable Class<?extendsAnnotation>[] qualifiers,@Nullable Supplier<T> supplier,@Nullable BeanDefinitionCustomizer[] customizers){//创建一个AnnotatedGenericBeanDefinition
		AnnotatedGenericBeanDefinition abd=newAnnotatedGenericBeanDefinition(beanClass);if(this.conditionEvaluator.shouldSkip(abd.getMetadata())){return;}......................................//进行beanDefinition注册
		BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder,this.registry);}

refresh()方法

refresh()方法，每个方法的作用请看注释，这里比较重要的是两个方法是invokeBeanFactoryPostProcessors(beanFactory)和finishBeanFactoryInitialization(beanFactory)分别进行类扫描和依赖注入以及AOP

@Overridepublicvoidrefresh()throws BeansException, IllegalStateException{synchronized(this.startupShutdownMonitor){// Prepare this context for refreshing.//准备工作包括设置启动时间，是否激活标志位，初始化属性源（property source）配置prepareRefresh();// Tell the subclass to refresh the internal bean factory.//如果是基于XML配置，并BeanFactory工厂不是在构造函数初始的时候进行实例化的，而是调用这个方法。
			ConfigurableListableBeanFactory beanFactory=obtainFreshBeanFactory();// Prepare the bean factory for use in this context.//对BeanFactory功能进行填充prepareBeanFactory(beanFactory);try{// Allows post-processing of the bean factory in context subclasses.//目前是个空方法，如果有需要由子类进行扩展postProcessBeanFactory(beanFactory);// Invoke factory processors registered as beans in the context.//在spring环境中去执行已经被注册的 BeanFactoryPostProcessors，类的扫描就是在这里进行的，它的作用是在//bean初始化之前做一些干预。invokeBeanFactoryPostProcessors(beanFactory);// Register bean processors that intercept bean creation.//注册BeanPostProcessors，BeanPostProcessors的作用是// 在bean初始化的时候进行干预，比如说进行AOP，这里只是注册，并不会执行registerBeanPostProcessors(beanFactory);// Initialize message source for this context.//为上下文初始化Message源，即不同的语言的消息体，国际化处理initMessageSource();// Initialize event multicaster for this context.//初始化应用消息广播器，并放入 applicationEventMulticasterinitApplicationEventMulticaster();// Initialize other special beans in specific context subclasses.//留给子类初始化其他的BeanonRefresh();// 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.//这个方法非常重要，依赖注入和AOP就是在这里进行的。finishBeanFactoryInitialization(beanFactory);// Last step: publish corresponding event.//完成刷新过程，通知生命周期处理器lifecycleProcessor刷新过程，同时发出ContextRefreshEvent通知别人。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();}}}
  • 作者：在下喵星人
  • 原文链接：https://blog.csdn.net/qq_22685435/article/details/116419305
    更新时间：2022-06-15 11:38:29