Spring源码讲解之parseBeanDefinitionElement

parseBeanDefinitionElement 方法是在 org.springframework.beans.factory.xml.BeanDefinitionParserDelegate 类中定义的&＃xff0c;主要作用是解析 bean 元素并将其结果赋值给 org.springframework.beans.factory.config.BeanDefinitionHolder 实例进行存储。 该方法接收一个类型为 org.w3c.dom.Element 的参数&＃xff0c;返回值类为 org.springframework.beans.factory.config.BeanDefinitionHolder。该方法会在org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.processBeanDefinition(Element, BeanDefinitionParserDelegate) 方法中调用。

源码

&＃64;Nullable
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) {return parseBeanDefinitionElement(ele, null);
}


parseBeanDefinitionElement 方法的实现

&＃64;Nullable
public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, &＃64;Nullable BeanDefinition containingBean) {// 获取 id 属性String id &＃61; ele.getAttribute(ID_ATTRIBUTE);// 获取 name 属性String nameAttr &＃61; ele.getAttribute(NAME_ATTRIBUTE);List<String> aliases &＃61; new ArrayList<>();if (StringUtils.hasLength(nameAttr)) {// 解析 name 属性中的值String[] nameArr &＃61; StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);aliases.addAll(Arrays.asList(nameArr));}String beanName &＃61; id;if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {beanName &＃61; aliases.remove(0);if (logger.isTraceEnabled()) {logger.trace("No XML &＃39;id&＃39; specified - using &＃39;" &＃43; beanName &＃43;"&＃39; as bean name and " &＃43; aliases &＃43; " as aliases");}}if (containingBean &＃61;&＃61; null) {// 检查 bean 名称和 bean 别名是否唯一checkNameUniqueness(beanName, aliases, ele);}// 重点方法// 解析 bean 元素到 BeanDefinition 中AbstractBeanDefinition beanDefinition &＃61; parseBeanDefinitionElement(ele, beanName, containingBean);if (beanDefinition !&＃61; null) {// 如果 beanName 为空&＃xff0c;通过 beanDefinition 信息生成一个 beanNameif (!StringUtils.hasText(beanName)) {try {if (containingBean !&＃61; null) {beanName &＃61; BeanDefinitionReaderUtils.generateBeanName(beanDefinition, this.readerContext.getRegistry(), true);}else {beanName &＃61; this.readerContext.generateBeanName(beanDefinition);// Register an alias for the plain bean class name, if still possible,// if the generator returned the class name plus a suffix.// This is expected for Spring 1.2/2.0 backwards compatibility.String beanClassName &＃61; beanDefinition.getBeanClassName();if (beanClassName !&＃61; null &&beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&!this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {aliases.add(beanClassName);}}if (logger.isTraceEnabled()) {logger.trace("Neither XML &＃39;id&＃39; nor &＃39;name&＃39; specified - " &＃43;"using generated bean name [" &＃43; beanName &＃43; "]");}}catch (Exception ex) {error(ex.getMessage(), ele);return null;}}String[] aliasesArray &＃61; StringUtils.toStringArray(aliases);return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);}return null;
}


parseBeanDefinitionElement 方法的实现

&＃64;Nullable
public AbstractBeanDefinition parseBeanDefinitionElement(Element ele, String beanName, &＃64;Nullable BeanDefinition containingBean) {// 记录 bean 的解析状态this.parseState.push(new BeanEntry(beanName));String className &＃61; null;if (ele.hasAttribute(CLASS_ATTRIBUTE)) {// 获取 calss 属性的值className &＃61; ele.getAttribute(CLASS_ATTRIBUTE).trim();}String parent &＃61; null;if (ele.hasAttribute(PARENT_ATTRIBUTE)) {// 获取 parent 属性的值parent &＃61; ele.getAttribute(PARENT_ATTRIBUTE);}try {// 创建一个 AbstractBeanDefinition 实例// 默认类型是 org.springframework.beans.factory.support.GenericBeanDefinitionAbstractBeanDefinition bd &＃61; createBeanDefinition(className, parent);// 解析 bean 定义相关的属性parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));// 解析 meta 子元素parseMetaElements(ele, bd);// 解析 lookup-method 子元素parseLookupOverrideSubElements(ele, bd.getMethodOverrides());// 解析 replaced-method 子元素parseReplacedMethodSubElements(ele, bd.getMethodOverrides());// 解析 constructor-arg 子元素parseConstructorArgElements(ele, bd);// 解析 property 子元素parsePropertyElements(ele, bd);// 解析 qualifier 子元素parseQualifierElements(ele, bd);bd.setResource(this.readerContext.getResource());bd.setSource(extractSource(ele));return bd;}catch (ClassNotFoundException ex) {error("Bean class [" &＃43; className &＃43; "] not found", ele, ex);}catch (NoClassDefFoundError err) {error("Class that bean class [" &＃43; className &＃43; "] depends on not found", ele, err);}catch (Throwable ex) {error("Unexpected failure during bean definition parsing", ele, ex);}finally {this.parseState.pop();}return null;
}


parseBeanDefinitionElement 方法讲解完毕&＃xff0c;部分方法没有进行详细讲解&＃xff08;例如&＃xff1a;parseBeanDefinitionAttributes、parseMetaElements 等方法&＃xff09;&＃xff0c;此部分代码都在 org.springframework.beans.factory.xml.BeanDefinitionParserDelegate 类中进行定义和实现&＃xff0c;想了解的朋友可以去此类中进行查看。