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

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。