Spring BeanDefinitionDocumentReader

  • Author: HuiFer
  • 源码浏览仓库: SourceHot-spring
  • 全门路: org.springframework.beans.factory.xml.BeanDefinitionDocumentReader
/** * SPI for parsing an XML document that contains Spring bean definitions. * Used by {@link XmlBeanDefinitionReader} for actually parsing a DOM document. * * <p>Instantiated per document to parse: implementations can hold * state in instance variables during the execution of the * {@code registerBeanDefinitions} method &mdash; for example, global * settings that are defined for all bean definitions in the document. * * * <p>bean定义文档读取</p> * @author Juergen Hoeller * @author Rob Harrop * @since 18.12.2003 * @see XmlBeanDefinitionReader#setDocumentReaderClass */public interface BeanDefinitionDocumentReader { /** * Read bean definitions from the given DOM document and * register them with the registry in the given reader context. * 注册 bean 定义 * @param doc the DOM document * @param readerContext the current context of the reader * (includes the target registry and the resource being parsed) * @throws BeanDefinitionStoreException in case of parsing errors */ void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) throws BeanDefinitionStoreException;}

  • 通过正文咱们能够晓得这个接口定义的行为如下

    1. 读取xml配置文件, 转换成 Spring bean definition
    2. 将 Spring bean definition 放入内存中
    • 办法作用
    1. 读取给定文档, 转换成 Spring bean definition 放入内存

registerBeanDefinitions

  • 接口定义的办法
@Overridepublic void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) { this.readerContext = readerContext; doRegisterBeanDefinitions(doc.getDocumentElement());}
  • 最终会交给doRegisterBeanDefinitions执行

doRegisterBeanDefinitions

 @SuppressWarnings("deprecation")  // for Environment.acceptsProfiles(String...) protected void doRegisterBeanDefinitions(Element root) { // Any nested <beans> elements will cause recursion in this method. In // order to propagate and preserve <beans> default-* attributes correctly, // keep track of the current (parent) delegate, which may be null. Create // the new (child) delegate with a reference to the parent for fallback purposes, // then ultimately reset this.delegate back to its original (parent) reference. // this behavior emulates a stack of delegates without actually necessitating one. BeanDefinitionParserDelegate parent = this.delegate; // 创立 BeanDefinitionParserDelegate this.delegate = createDelegate(getReaderContext(), root, parent); if (this.delegate.isDefaultNamespace(root)) { // profile 属性获取 String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE); // 是否存在 profile if (StringUtils.hasText(profileSpec)) { // profile 切分后的数据 String[] specifiedProfiles = StringUtils.tokenizeToStringArray( profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS); // We cannot use Profiles.of(...) since profile expressions are not supported // in XML config. See SPR-12458 for details. if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) { if (logger.isDebugEnabled()) { logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec + "] not matching: " + getReaderContext().getResource()); } return; } } } // 前置解决 preProcessXml(root); // bean definition 解决 parseBeanDefinitions(root, this.delegate); // 后置 xml 解决 postProcessXml(root); this.delegate = parent; }
createDelegate
this.delegate = createDelegate(getReaderContext(), root, parent)

  • 参数阐明

    1. xml 解析器
    2. element xml节点
    3. 父BeanDefinitionParserDelegate
protected final XmlReaderContext getReaderContext() { Assert.state(this.readerContext != null, "No XmlReaderContext available"); return this.readerContext;}
preProcessXml
  • 前置解决办法为空
parseBeanDefinitions

  • 解析标签

    1. 标签 import
    2. 标签 alias
    3. 标签 bean
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) { if (delegate.isDefaultNamespace(root)) { // 子节点列表 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)) { // 解决标签的办法 parseDefaultElement(ele, delegate); } else { // 解决自定义标签 delegate.parseCustomElement(ele); } } } } else { // 解决自定义标签 delegate.parseCustomElement(root); }}
postProcessXml
  • 后置解决办法为空

parseDefaultElement

  • 将parseDefaultElement提出残缺的解析
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) { // 解析 import 标签 if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) { importBeanDefinitionResource(ele); } // 解析 alias 标签 else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) { processAliasRegistration(ele); } // 解析 bean 标签 else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { processBeanDefinition(ele, delegate); } // 解析 beans 标签 // 嵌套的 beans else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // recurse doRegisterBeanDefinitions(ele); }}

importBeanDefinitionResource

protected void importBeanDefinitionResource(Element ele) { // 获取 resource 属性 String location = ele.getAttribute(RESOURCE_ATTRIBUTE); if (!StringUtils.hasText(location)) { getReaderContext().error("Resource location must not be empty", ele); return; } // Resolve system properties: e.g. "${user.dir}" // 解决配置文件占位符 location = getReaderContext().getEnvironment().resolveRequiredPlaceholders(location); // 资源汇合 Set<Resource> actualResources = new LinkedHashSet<>(4); // Discover whether the location is an absolute or relative URI // 是不是相对地址 boolean absoluteLocation = false; try { // 1. 判断是否为 url // 2. 通过转换成URI判断是否是相对地址 absoluteLocation = ResourcePatternUtils.isUrl(location) || ResourceUtils.toURI(location).isAbsolute(); } catch (URISyntaxException ex) { // cannot convert to an URI, considering the location relative // unless it is the well-known Spring prefix "classpath*:" } // Absolute or relative? if (absoluteLocation) { try { // 获取 import 的数量 int importCount = getReaderContext().getReader().loadBeanDefinitions(location, actualResources); if (logger.isTraceEnabled()) { logger.trace("Imported " + importCount + " bean definitions from URL location [" + location + "]"); } } catch (BeanDefinitionStoreException ex) { getReaderContext().error( "Failed to import bean definitions from URL location [" + location + "]", ele, ex); } } else { // No URL -> considering resource location as relative to the current file. try { // import 的数量 int importCount; // 资源信息 Resource relativeResource = getReaderContext().getResource().createRelative(location); // 资源是否存在 if (relativeResource.exists()) { // 确定加载的bean定义数量 importCount = getReaderContext().getReader().loadBeanDefinitions(relativeResource); // 退出资源汇合 actualResources.add(relativeResource); } // 资源不存在解决计划 else { // 获取资源URL的数据 String baseLocation = getReaderContext().getResource().getURL().toString(); // 获取import数量 importCount = getReaderContext().getReader().loadBeanDefinitions( StringUtils.applyRelativePath(baseLocation, location), actualResources); } if (logger.isTraceEnabled()) { logger.trace("Imported " + importCount + " bean definitions from relative location [" + location + "]"); } } catch (IOException ex) { getReaderContext().error("Failed to resolve current resource location", ele, ex); } catch (BeanDefinitionStoreException ex) { getReaderContext().error( "Failed to import bean definitions from relative location [" + location + "]", ele, ex); } } Resource[] actResArray = actualResources.toArray(new Resource[0]); // 唤醒 import 处理事件 getReaderContext().fireImportProcessed(location, actResArray, extractSource(ele));}

processAliasRegistration

  • org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader#processAliasRegistration
  • alias 标签解析
protected void processAliasRegistration(Element ele) { // 获取 name 属性 String name = ele.getAttribute(NAME_ATTRIBUTE); // 获取 alias 属性 String alias = ele.getAttribute(ALIAS_ATTRIBUTE); boolean valid = true; // name 属性验证 if (!StringUtils.hasText(name)) { getReaderContext().error("Name must not be empty", ele); valid = false; } // alias 属性验证 if (!StringUtils.hasText(alias)) { getReaderContext().error("Alias must not be empty", ele); valid = false; } if (valid) { try { getReaderContext().getRegistry().registerAlias(name, alias); } catch (Exception ex) { getReaderContext().error("Failed to register alias '" + alias + "' for bean with name '" + name + "'", ele, ex); } // 事件触发 getReaderContext().fireAliasRegistered(name, alias, extractSource(ele)); }}

processBeanDefinition

  • org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader#processBeanDefinition
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); if (bdHolder != null) { // bean definition 装璜 bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // Register the final decorated instance. // 注册beanDefinition BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry()); } catch (BeanDefinitionStoreException ex) { getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, ex); } // Send registration event. // component注册事件触发 getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder)); }}
  • BeanDefinitionParserDelegate

ClassPathContextResource

  • 创立出资源接口
protected static class ClassPathContextResource extends ClassPathResource implements ContextResource { public ClassPathContextResource(String path, @Nullable ClassLoader classLoader) { super(path, classLoader); } @Override public String getPathWithinContext() { return getPath(); } @Override public Resource createRelative(String relativePath) { String pathToUse = StringUtils.applyRelativePath(getPath(), relativePath); return new ClassPathContextResource(pathToUse, getClassLoader()); }}

fireImportProcessed

/** * Fire an import-processed event. * * 执行 import 事件 * @param importedResource 导入的文件 * @param actualResources 资源门路 * @param source source */public void fireImportProcessed(String importedResource, Resource[] actualResources, @Nullable Object source) { this.eventListener.importProcessed(new ImportDefinition(importedResource, actualResources, source));}

ReaderEventListener

事件监听

关注的办法

void importProcessed(ImportDefinition importDefinition);

实现

  • org.springframework.beans.testfixture.beans.CollectingReaderEventListener#importProcessed
@Overridepublic void importProcessed(ImportDefinition importDefinition) { this.imports.add(importDefinition);}

放入 imports 列表中
关注办法

 void aliasRegistered(AliasDefinition aliasDefinition);```实现- `org.springframework.beans.testfixture.beans.CollectingReaderEventListener#aliasRegistered`

@Override
public void aliasRegistered(AliasDefinition aliasDefinition) {
// 获取曾经注册过的beanName对应的别名
List<AliasDefinition> aliases = this.aliasMap.get(aliasDefinition.getBeanName()); if (aliases == null) { aliases = new ArrayList<>(); // beanName 和 别名对应关系设置
this.aliasMap.put(aliasDefinition.getBeanName(), aliases); } // 别名列表增加
aliases.add(aliasDefinition);}

关注办法

void componentRegistered(ComponentDefinition componentDefinition);

实现- `org.springframework.beans.testfixture.beans.CollectingReaderEventListener#componentRegistered`

@Override
public void componentRegistered(ComponentDefinition componentDefinition) {
this.componentDefinitions.put(componentDefinition.getName(), componentDefinition);}