Spring源码学习--Spring配置解析文件ApplicationContext.xml（一）

小灰灰 2022-06-14 01:50 202阅读 0赞

接下来我们用多篇文件对Spring解析Bean配置文件ApplicationContext.xml的过程进行一系列的了解，了解Spring对我们在ApplicationContext.xml中注入的Bean的解析流程。

AbstractApplicationContext：中会初始化Bean容器

@Override
    	public void refresh() throws BeansException, IllegalStateException {
    		synchronized (this.startupShutdownMonitor) {
    		
    			...........
    			
    			//获取bean容器
    			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
    			
    			...........			
    
    	}

在obtainFreshBeanFactory中会初始化容器并返回初始化后的容器

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
    		//初始化bean容器
    		refreshBeanFactory();
    		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
    		if (logger.isDebugEnabled()) {
    			logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
    		}
    		return beanFactory;
    	}

AbstractRefreshableApplicationContext类中：在refreshBeanFactory中会初始化容器，并加载配置文件loadBeanDefinitions

@Override
    	protected final void refreshBeanFactory() throws BeansException {
    		if (hasBeanFactory()) {
    			destroyBeans();
    			closeBeanFactory();
    		}
    		try {
    			//创建Bean容器
    			DefaultListableBeanFactory beanFactory = createBeanFactory();
    			beanFactory.setSerializationId(getId());
    			customizeBeanFactory(beanFactory);
    			//加载配置文件
    			loadBeanDefinitions(beanFactory);
    			synchronized (this.beanFactoryMonitor) {
    				this.beanFactory = beanFactory;
    			}
    		}
    		catch (IOException ex) {
    			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
    		}
    	}

接下来我们看一下loadBeanDefinitions所做的操作，其实现在AbstractXmlApplicationContext中，简单来说就是初始化了XmlBeanDefinitionReader， XmlBeanDefinitionReader是用来解析ApplicationContext.xml这个文件的。

@Override
    	protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
    		// Create a new XmlBeanDefinitionReader for the given BeanFactory.
    		//创建ApplicationContext.xml文件的处理类XmlBeanDefinitionReader
    		XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
    
    		// Configure the bean definition reader with this context's
    		// resource loading environment.
    		beanDefinitionReader.setEnvironment(this.getEnvironment());
    		beanDefinitionReader.setResourceLoader(this);
    		beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
    
    		// Allow a subclass to provide custom initialization of the reader,
    		// then proceed with actually loading the bean definitions.
    		initBeanDefinitionReader(beanDefinitionReader);
    		//加载ApplicationContext.xml文件
    		loadBeanDefinitions(beanDefinitionReader);
    	}

接下来ApplicationContext.xml解析的工作是在XmlBeanDefinitionReader中

protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
    		Resource[] configResources = getConfigResources();//获取配置文件路径
    		if (configResources != null) {
    			reader.loadBeanDefinitions(configResources);
    		}
    		String[] configLocations = getConfigLocations();
    		if (configLocations != null) {
    			reader.loadBeanDefinitions(configLocations);
    		}
    	}

总结：简单来说在ApplicationContext中所做的操作是初始化了一个BeanFactory和XmlBeanDefinitionReader，其中XmlBeanDefinitionReader是用来解析Spring的xml配置文件的，接下来我们会用一篇博客介绍一下 XmlBeanDefinitionReader解析Spring的配置文件xml相关的知识。