spring 筆記4 BeanDefinitionReader

原創

2020-02-21 23:57

BeanDefinitionReader 如何從resource把BeanDefinition註冊到工廠

BeanDefinitionReader
    AbstractBeanDefinitionReader
	    XmlBeanDefinitionReader

1 、BeanDefinitionReader#loadBeanDefinitions(Resource resource)
從指定資源加載BeanDefinition

2、XmlBeanDefinitionReader中實現
最終調到doLoadBeanDefinitions(InputSource inputSource, Resource resource)
得到document，xml結構

Document doc = this.documentLoader.loadDocument(
					inputSource, getEntityResolver(), this.errorHandler, validationMode, isNamespaceAware());
 registerBeanDefinitions(doc, resource);
 
 調用BeanDefinitionDocumentReader#registerBeanDefinitions(doc, createReaderContext(resource))

3、public class DefaultBeanDefinitionDocumentReader implements BeanDefinitionDocumentReader
調用到方法

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);
					}
					else {
						delegate.parseCustomElement(ele);
					}
				}
			}
		}
		else {
			delegate.parseCustomElement(root);
		}
	}
	
	private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
		if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
			importBeanDefinitionResource(ele);
		}
		else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
			processAliasRegistration(ele);
		}
		else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
			processBeanDefinition(ele, delegate);
		}
		else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
			// recurse
			doRegisterBeanDefinitions(ele);
		}
	}
	
	processBeanDefinition(ele, delegate);
	BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
	//BeanDefinitionParserDelegate這個工具類從xml配置信息得到BeanDefinition
	BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
	//getReaderContext().getRegistry()即爲DefaultListableBeanFactory，方法內即是使用registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
	把BeanDefinition註冊到工廠