Spring IoC 容器启动时做了什么？

小灰灰 2022-10-31 01:45 243阅读 0赞

BeanFactory 是 Spring IoC 容器的底层实现，以 XmlBeanFactory 为例

1.  XmlBeanFactory 构造方法需要 Resource 对象
2.  XmlBeanDefinitionReader\#loadBeanDefinitions 方法解析 xml Resource、获取和注册 BeanDefinition

代码入口：

public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
    	super(parentBeanFactory);
    	this.reader.loadBeanDefinitions(resource);
    }

**ApplicationContext** 是 BeanFactory 的超集。ApplicationContext 的启动主要是体现在 AbstractApplicationContext\#refresh 方法上，进行了 IoC 配置元信息读取和解析、获取设置持有的 BeanFactory 对象、BeanFactoryPostProcessors 注册、注册各种 BeanPostProcessor 用于拦截和处理 Bean 的创建、Spring 事件发布、国际化等。

代码入口：

@Override
    public void refresh() throws BeansException, IllegalStateException {
    	synchronized (this.startupShutdownMonitor) {
    		// Prepare this context for refreshing.
    		prepareRefresh();
    
    		// Tell the subclass to refresh the internal bean factory.
    		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();
    		}
    	}
    }

--------------------

### 【Java学习资源】整理推荐 ###

*  [Bean 的作用域][Bean]
 *  [maven 集成 tomcat 以 jar 的方式打包 web 应用][maven _ tomcat _ jar _ web]
 *  [Spring 依赖注入与依赖查找来源的区别][Spring]
 *  [Spring 依赖注入的处理过程与 DependencyDescriptor 的说明][Spring _ DependencyDescriptor]
 *  [Spring 各种 Aware 接口回调注入][Spring _ Aware]
 *  [Spring Bean 生命周期内的 Exception 复现][Spring Bean _ Exception]
 *  [Spring 内建 Bean][Spring _ Bean]
 *  [Spring Bean 的别名][Spring Bean]
 *  [Spring Bean 未指定名称的命名规则][Spring Bean 1]
 *  [Bean 何时被 GC][Bean _ GC]
 *  [Spring Bean 延迟加载][Spring Bean 2]
 *  [ObjectFactory 与 BeanFactory 的区别][ObjectFactory _ BeanFactory]
 *  [Bean 销毁的方式与顺序][Bean 1]
 *  [Bean 初始化的方式与顺序][Bean 2]
 *  [Bean 的实例化方式][Bean 3]
 *  [Bean的注册方式][Bean 4]
 *  [什么是 BeanDefinition？][BeanDefinition]
 *  [Spring IoC 容器启动时做了什么？][Spring IoC]
 *  [BeanFactory 与 FactoryBean 的区别][BeanFactory _ FactoryBean]
 *  [BeanFactory 与 ApplicationContext 的区别][BeanFactory _ ApplicationContext]
 *  [Spring IoC 依赖注入的实现方式][Spring IoC 1]
 *  [Spring IoC 依赖注入(支持哪些数据类型？)][Spring IoC 2]
 *  [Spring bean 依赖查找][Spring bean]
 *  [Spring-IoC][]
 *  [Spring 的核心特性][Spring 1]

--------------------

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*  [基础与语法][Link 1]
 *  [集合][Link 2]
 *  [网络编程][Link 3]
 *  [并发编程][Link 4]
 *  [Web][]
 *  [安全][Link 5]
 *  [设计模式][Link 6]
 *  [框架][Link 7]
 *  [算法与数据结构][Link 8]
 *  [异常][Link 9]
 *  [文件解析与生成][Link 10]
 *  [Linux][]
 *  [MySQL][]
 *  [Oracle][]
 *  [Redis][]
 *  [Dubbo][]

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[Linux]: https://www.javanav.com/interview/00cccb81729540d1923bd0a0ef49533a.html
[MySQL]: https://www.javanav.com/interview/d311e78502a845f1a4bb307bd6aec2b3.html
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[Dubbo]: https://www.javanav.com/interview/9a3e7a7740324757abaab953f7ebc455.html