Spring框架核心源代码的分析及其感受-3

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException { 
       XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);  //从这块代码
      可以发现XML的解析估计是在这里发生的，也就是这个Reader来读取的，
       ....
       loadBeanDefinitions(beanDefinitionReader);
 }

 

….

protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {

       Resource[] configResources = getConfigResources();

       if (configResources != null) {

           reader.loadBeanDefinitions(configResources); //果然是由Reader来加载和解析XML并载入BeanDefinition中的！
       }

       String[] configLocations = getConfigLocations();

       if (configLocations != null) {

           reader.loadBeanDefinitions(configLocations);

       }

    }

 

protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)

           throws BeanDefinitionStoreException {

       try {

           int validationMode = getValidationModeForResource(resource);

           Document doc = this.documentLoader.loadDocument(

                  inputSource, getEntityResolver(), this.errorHandler, validationMode, isNamespaceAware());

           //在这里激发注册过程

           return registerBeanDefinitions(doc, resource);

       }

       catch (BeanDefinitionStoreException ex) {

           throw ex;

       }

       catch (SAXParseException ex) {

    …

}

 

从上上面的代码中，你可以肯定的是 XML 是在 XmlBeanDefinitionReader 类中解析的，解析到 BeanDefinition 中！进入 XmlBeanDefinitionReader 中，看一看：

 

public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {

       Assert.notNull(encodedResource, "EncodedResource must not be null");

       if (logger.isInfoEnabled()) {

           logger.info("Loading XML bean definitions from " + encodedResource.getResource());

       }

 

       Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();

       if (currentResources == null) {

           currentResources = new HashSet<EncodedResource>(4);

           this.resourcesCurrentlyBeingLoaded.set(currentResources);

       }

       if (!currentResources.add(encodedResource)) {

           throw new BeanDefinitionStoreException(

                  "Detected cyclic loading of " + encodedResource + " - check your import definitions!");

       }

       try {

           InputStream inputStream = encodedResource.getResource().getInputStream();

           try {

              InputSource inputSource = new InputSource(inputStream);

              if (encodedResource.getEncoding() != null) {

                  inputSource.setEncoding(encodedResource.getEncoding());

              }

              //这里是具体加载的实现逻辑

              return doLoadBeanDefinitions(inputSource, encodedResource.getResource());

             ...... 
           } 

 

哈哈，你也可以看到 ReaourceLoader 确实是加载 XML 的！进入 doLoadBeanDefinitions 方法！

-------------TODO,这里需要补充一下

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

看到了吧？就是一个大家经常用到 SAX 的 Document 来取得 XML 文档的，在进入 registerBeanDefinitions 看看！

 

public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {

       BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();

       if (documentReader instanceof DefaultBeanDefinitionDocumentReader) {

           ((DefaultBeanDefinitionDocumentReader)documentReader).setEnvironment(this.getEnvironment());

       }

       int countBefore = getRegistry().getBeanDefinitionCount();

       documentReader.registerBeanDefinitions(doc, createReaderContext(resource));//在这里注册，也就是注册到一个共享的容器中，比如Map.这样缓存起来后，spring其他部分就可以从一个共享的位置加载目标BeanDefinition了（通过BeanDefinition的名字）。

       return getRegistry().getBeanDefinitionCount() - countBefore;

    }

 

在进入 documentReader.registerBeanDefinitions 看看！

protected void doRegisterBeanDefinitions(Element root) {

       String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);

       boolean isCandidate = false;

       if (profileSpec == null || profileSpec.equals("")) {

           isCandidate = true;

       } else {

           String[] profiles = commaDelimitedListToStringArray(trimAllWhitespace(profileSpec));

           for (String profile : profiles) {

              if (this.environment.getActiveProfiles().contains(profile)) {

                  isCandidate = true;

                  break;

              }

           }

       }

 

       if (!isCandidate) {

           return;

       }

       BeanDefinitionParserDelegate parent = this.delegate;//Deletgate里面包含着多有XML属性和elemnt的结构信息

       this.delegate = createHelper(readerContext, root, parent);

 

       preProcessXml(root);

       parseBeanDefinitions(root, this.delegate);
       postProcessXml(root);