Step 1. XmlBeanFactory

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

Step 2.XmlBeanDefinitionReader

// 1. 呼叫方法 loadBeanDefinitions
public int loadBeanDefinitions
 
(Resource resource) throws BeanDefinitionStoreException {
        return loadBeanDefinitions(new EncodedResource(resource));
}
// 2. 呼叫方法 doLoadBeanDefinitions
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
            throws BeanDefinitionStoreException {
        //......
 

            return registerBeanDefinitions(doc, resource);
        //......
}
// 3. 呼叫方法 registerBeanDefinitions
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
        BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
        documentReader.setEnvironment(getEnvironment());
        int
 
 countBefore = getRegistry().getBeanDefinitionCount();
        documentReader.registerBeanDefinitions(doc, createReaderContext(resource)); //核心
        return getRegistry().getBeanDefinitionCount() - countBefore;
}

Step 3.DefaultBeanDefinitionDocumentReader

public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
        this.readerContext = readerContext;
        Element root = doc.getDocumentElement();
        doRegisterBeanDefinitions(root); // 核心
}

protected void doRegisterBeanDefinitions(Element root) {
       //....
       // 對profile屬性解析
        parseBeanDefinitions(root, this.delegate);
        //....
}

protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
        if (delegate.isDefaultNamespace(root)) {
            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)) {
                        parseDefaultElement(ele, delegate); // 預設空間解析
                    }
                    else {
                        delegate.parseCustomElement(ele); // 自定義全名空間解析
                    }
                }
            }
        }
        else {
         delegate.parseCustomElement(root);//自定義全名空間解析
        }
    }

// 預設標籤解析
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
        if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
            importBeanDefinitionResource(ele); // import標籤解析
        }
        else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
            processAliasRegistration(ele); // alias標籤解析
        }
        else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
            processBeanDefinition(ele, delegate); // bean標籤解析
        }
        else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
            // recurse
            doRegisterBeanDefinitions(ele); // beans標籤解析
        }
    }

protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
        //委託給BeanDefinitionParserDelegate解析
        BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
        if (bdHolder != null) {
            //委託給 BeanDefinitionParserDelegate 解析自定義標籤，最後呼叫delegate.parseCustomElement(ele);
            bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
            try {
                // Register the final decorated instance.
                BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
            }
            catch (BeanDefinitionStoreException ex) {
                getReaderContext().error("Failed to register bean definition with name '" +
                        bdHolder.getBeanName() + "'", ele, ex);
            }
            // Send registration event.
            getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
        }
    }

Step 4. BeanDefinitionParserDelegate

1. bean常見標籤解析

// bean常見標籤解析
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
        //......
        //核心
        AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
        //......
}

//詳細解析過程
public AbstractBeanDefinition parseBeanDefinitionElement(
            Element ele, String beanName, BeanDefinition containingBean) {
            AbstractBeanDefinition bd = createBeanDefinition(className, parent);

            parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
            bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));

            parseMetaElements(ele, bd);
            parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
            parseReplacedMethodSubElements(ele, bd.getMethodOverrides());

            parseConstructorArgElements(ele, bd);
            parsePropertyElements(ele, bd);
            parseQualifierElements(ele, bd);

            bd.setResource(this.readerContext.getResource());
            bd.setSource(extractSource(ele));
}

1. bean自定義標籤解析

BeanDefinitionParserDelegate類

public BeanDefinition parseCustomElement(Element ele) {
        return parseCustomElement(ele, null);
}

public BeanDefinition parseCustomElement(Element ele, BeanDefinition containingBd) {
        String namespaceUri = getNamespaceURI(ele);
        NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri);
        //.......
        return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd));
}

DefaultNamespaceHandlerResolver類

public NamespaceHandler resolve(String namespaceUri) {
       // 獲取所有已經配置的handler資訊
        Map<String, Object> handlerMappings = getHandlerMappings();
       // 獲取處理該名稱空間的handler
        Object handlerOrClassName = handlerMappings.get(namespaceUri);
        // ......
    }

NamespaceHandlerSupport類

public BeanDefinition parse(Element element, ParserContext parserContext) {
    return findParserForElement(element, parserContext).parse(element, parserContext);
}

AbstractBeanDefinitionParser類

@Override
public final BeanDefinition parse(Element element, ParserContext parserContext) {
        AbstractBeanDefinition definition = parseInternal(element, parserContext);
        //......
        return definition;
}

AbstractSingleBeanDefinitionParser類

protected final AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition();
        String parentName = getParentName(element);
        if (parentName != null) {
            builder.getRawBeanDefinition().setParentName(parentName);
        }
        Class<?> beanClass = getBeanClass(element); // 使用者override方法
        if (beanClass != null) {
            builder.getRawBeanDefinition().setBeanClass(beanClass);
        }
        else {
            String beanClassName = getBeanClassName(element);
            if (beanClassName != null) {
                builder.getRawBeanDefinition().setBeanClassName(beanClassName);
            }
        }
        builder.getRawBeanDefinition().setSource(parserContext.extractSource(element));
        if (parserContext.isNested()) {
            // Inner bean definition must receive same scope as containing bean.
            builder.setScope(parserContext.getContainingBeanDefinition().getScope());
        }
        if (parserContext.isDefaultLazyInit()) {
            // Default-lazy-init applies to custom bean definitions as well.
            builder.setLazyInit(true);
        }
        // 呼叫自定義的解析函式
        doParse(element, parserContext, builder); // 使用者override方法
        return builder.getBeanDefinition();
}