spring-beanFactory一

下面以XmlBeanFactory为例来简单看一下beanFactory对xml的处理过程。

ResourceLoader resourceLoader = new DefaultResourceLoader();
//ResourceLoader类似一个工厂，getResource可以通过传入的路径判断返回什么类型的Resource，
//比如，如果路径以classpath:开头就会返回一个代表该路径的ClassPathResource实例
org.springframework.core.io.Resource resource = resourceLoader.getResource("spring/spring-test.xml");
XmlBeanFactory factory = new XmlBeanFactory(resource);

public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
    super(parentBeanFactory);
    //private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);
    //这里只看到Resource，具体Resource由实现决定，beanFactory关注Resource的getInputStream，
    //比如ClassPathResource的getInputStream是return this.clazz.getResourceAsStream(this.path)这种形式，
    //FileSystemResource的getInputStream是new FileInputStream(this.file)这种形式，
    //策略模式
    this.reader.loadBeanDefinitions(resource);
}

@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
    //EncodedResource只是给Resource设定解码字符集，在使用reader时会用到，直接处理InputStream字节流时不会涉及
    return loadBeanDefinitions(new EncodedResource(resource));
}

//loadBeanDefinitions的主要逻辑，有删减
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
    InputStream inputStream = encodedResource.getResource().getInputStream();
    InputSource inputSource = new InputSource(inputStream);
    if (encodedResource.getEncoding() != null) {
        inputSource.setEncoding(encodedResource.getEncoding());
    }
    return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}

//doLoadBeanDefinitions的主要逻辑，有删减
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
            throws BeanDefinitionStoreException {
    //org.w3c.dom.Document
    Document doc = doLoadDocument(inputSource, resource);
    //注册bean definition，还未实例化
    return registerBeanDefinitions(doc, resource);
}

//doLoadDocument会调用DefaultDocumentLoader的loadDocument方法，根据xml文件是否存在DOCTYPE决定validationMode(DTD、XSD)
public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
        ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {
    //javax.xml.parsers.DocumentBuilderFactory.newInstance()，以及对DocumentBuilderFactory的一些简单配置，如setValidating
    DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
    //javax.xml.parsers.DocumentBuilder builder=factory.newDocumentBuilder()
    DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
    //解析得到org.w3c.dom.Document
    return builder.parse(inputSource);
}

//registerBeanDefinitions就是通过document注册bean定义，有删减
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
    this.readerContext = readerContext;
    //delegate是BeanDefinitionParserDelegate用于解析xml bean definitions
    this.delegate = createDelegate(getReaderContext(), root, parent);
    Element root = doc.getDocumentElement();
    NodeList nl = root.getChildNodes();
    for (int i = 0; i < nl.getLength(); i++) {
        Node node = nl.item(i);
        if (node instanceof Element) {
            Element ele = (Element) node;
            if (delegate.isDefaultNamespace(ele)) {
                //解析逻辑主要就是将使用delegate将ele解析为beanDefinition，并将beanDefinition注册在beanFactory的注册表上（其实就是map）
                parseDefaultElement(ele, delegate);
            }
            else {
                delegate.parseCustomElement(ele);
            }
        }
    }
}

至此，spring的xml配置文件就变成了beanFactroy中注册表中的bean definitions。