1.自定义标签的使用
https://www.cnblogs.com/lihao007/p/8455916.html
2.自定义标签的解析
@Nullable public BeanDefinition parseCustomElement(Element ele) { return parseCustomElement(ele, null); } @Nullable //containingBd为父类bean,对顶层元素的解析应设置为null public BeanDefinition parseCustomElement(Element ele, @Nullable BeanDefinition containingBd) { //获取对应的命名空间 String namespaceUri = getNamespaceURI(ele); if (namespaceUri == null) { return null; } //根据命名空间找到对应的NamespaceHandler NamespaceHandler handler = this.readerContext.getNamespaceHandlerResolver().resolve(namespaceUri); if (handler == null) { error("Unable to locate Spring NamespaceHandler for XML schema namespace [" + namespaceUri + "]", ele); return null; } //调用自定义的NamespaceHandler解析 return handler.parse(ele, new ParserContext(this.readerContext, this, containingBd)); }
自定义标签处理器
public NamespaceHandler resolve(String namespaceUri) { //获取所有已经配置的handler映射 Map<String, Object> handlerMappings = getHandlerMappings(); //根据命名空间找到对应的信息 Object handlerOrClassName = handlerMappings.get(namespaceUri); if (handlerOrClassName == null) { return null; } //已经做过解析的情况,直接从缓存读取 else if (handlerOrClassName instanceof NamespaceHandler) { return (NamespaceHandler) handlerOrClassName; } else { //没有做过解析,则返回的是类路径 String className = (String) handlerOrClassName; try { //使用反射将路径转化为类 Class<?> handlerClass = ClassUtils.forName(className, this.classLoader); if (!NamespaceHandler.class.isAssignableFrom(handlerClass)) { throw new FatalBeanException("Class [" + className + "] for namespace [" + namespaceUri + "] does not implement the [" + NamespaceHandler.class.getName() + "] interface"); } //初始化类 NamespaceHandler namespaceHandler = (NamespaceHandler) BeanUtils.instantiateClass(handlerClass); //调用自定义的NamespaceHandler的初始化方法 namespaceHandler.init(); //记录在缓存 handlerMappings.put(namespaceUri, namespaceHandler); return namespaceHandler; } catch (ClassNotFoundException ex) { throw new FatalBeanException("Could not find NamespaceHandler class [" + className + "] for namespace [" + namespaceUri + "]", ex); } catch (LinkageError err) { throw new FatalBeanException("Unresolvable class definition for NamespaceHandler class [" + className + "] for namespace [" + namespaceUri + "]", err); } } }
private Map<String, Object> getHandlerMappings() { //如果没有被缓存则开始进行缓存 Map<String, Object> handlerMappings = this.handlerMappings; if (handlerMappings == null) { synchronized (this) { handlerMappings = this.handlerMappings; if (handlerMappings == null) { if (logger.isTraceEnabled()) { logger.trace("Loading NamespaceHandler mappings from [" + this.handlerMappingsLocation + "]"); } try { //this.handlerMappingsLocation在构造函数中已经被初始化为:META-INF/Spring.handlers Properties mappings = PropertiesLoaderUtils.loadAllProperties(this.handlerMappingsLocation, this.classLoader); if (logger.isTraceEnabled()) { logger.trace("Loaded NamespaceHandler mappings: " + mappings); } handlerMappings = new ConcurrentHashMap<>(mappings.size()); //将Peoperties格式文件合并到Map格式的handlerMappings中 CollectionUtils.mergePropertiesIntoMap(mappings, handlerMappings); this.handlerMappings = handlerMappings; } catch (IOException ex) { throw new IllegalStateException( "Unable to load NamespaceHandler mappings from location [" + this.handlerMappingsLocation + "]", ex); } } } } return handlerMappings; }
标签解析
public BeanDefinition parse(Element element, ParserContext parserContext) { BeanDefinitionParser parser = findParserForElement(element, parserContext); return (parser != null ? parser.parse(element, parserContext) : null); }
private BeanDefinitionParser findParserForElement(Element element, ParserContext parserContext) { //获取元素名称 String localName = parserContext.getDelegate().getLocalName(element); //找到对应的解析器 BeanDefinitionParser parser = this.parsers.get(localName); if (parser == null) { parserContext.getReaderContext().fatal( "Cannot locate BeanDefinitionParser for element [" + localName + "]", element); } return parser; }
public final BeanDefinition parse(Element element, ParserContext parserContext) { AbstractBeanDefinition definition = parseInternal(element, parserContext); if (definition != null && !parserContext.isNested()) { try { String id = resolveId(element, definition, parserContext); if (!StringUtils.hasText(id)) { parserContext.getReaderContext().error( "Id is required for element '" + parserContext.getDelegate().getLocalName(element) + "' when used as a top-level tag", element); } String[] aliases = null; if (shouldParseNameAsAliases()) { String name = element.getAttribute(NAME_ATTRIBUTE); if (StringUtils.hasLength(name)) { aliases = StringUtils.trimArrayElements(StringUtils.commaDelimitedListToStringArray(name)); } } //将AbstractBeanDefinition转换为BeanDefinition并注册 BeanDefinitionHolder holder = new BeanDefinitionHolder(definition, id, aliases); registerBeanDefinition(holder, parserContext.getRegistry()); if (shouldFireEvents()) { //通知监听器 BeanComponentDefinition componentDefinition = new BeanComponentDefinition(holder); postProcessComponentDefinition(componentDefinition); parserContext.registerComponent(componentDefinition); } } catch (BeanDefinitionStoreException ex) { String msg = ex.getMessage(); parserContext.getReaderContext().error((msg != null ? msg : ex.toString()), element); return null; } } return definition; }
protected final AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) { BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(); String parentName = getParentName(element); if (parentName != null) { builder.getRawBeanDefinition().setParentName(parentName); } //获取自定义标签中的class Class<?> beanClass = getBeanClass(element); if (beanClass != null) { builder.getRawBeanDefinition().setBeanClass(beanClass); } else { //如果子类没有重写 则尝试检查子类是否重写 String beanClassName = getBeanClassName(element); if (beanClassName != null) { builder.getRawBeanDefinition().setBeanClassName(beanClassName); } } builder.getRawBeanDefinition().setSource(parserContext.extractSource(element)); BeanDefinition containingBd = parserContext.getContainingBeanDefinition(); if (containingBd != null) { // Inner bean definition must receive same scope as containing bean. builder.setScope(containingBd.getScope()); } if (parserContext.isDefaultLazyInit()) { // Default-lazy-init applies to custom bean definitions as well. builder.setLazyInit(true); } //调用子类重写的doParse方法进行解析 doParse(element, parserContext, builder); return builder.getBeanDefinition(); }