springAOP入口之AopNamespaceHandler.doc

springAOP入口之AopNamespaceHandler我们从spring.handlers入口开始看:/schema/aop=org.springframework.aop.config.AopNamespaceHandler1打开类AopNamespaceHandler，代码如下：package org.springframework.aop.config;import org.springframework.aop.aspectj.AspectJExpressionPointcut;import org.springframework.beans.factory.xml.BeanDefinitionParser;import org.springframework.beans.factory.xml.NamespaceHandlerSupport;/* * code NamespaceHandler for the code aop namespace. * * Provides a link org.springframework.beans.factory.xml.BeanDefinitionParser for the * code <aop:config> tag. A code config tag can include nested * code pointcut, code advisor and code aspect tags. * * The code pointcut tag allows for creation of named * link AspectJExpressionPointcut beans using a simple syntax: * * <aop:pointcut id="getNameCalls" expression="execution(* *.ITestBean.getName(.)"/> * * * Using the code advisor tag you can configure an link org.springframework.aop.Advisor * and have it applied to all relevant beans in you link org.springframework.beans.factory.BeanFactory * automatically. The code advisor tag supports both in-line and referenced * link org.springframework.aop.Pointcut Pointcuts: * * * <aop:advisor id="getAgeAdvisor" * pointcut="execution(* *.ITestBean.getAge(.)" * advice-ref="getAgeCounter"/> * * <aop:advisor id="getNameAdvisor" * pointcut-ref="getNameCalls" * advice-ref="getNameCounter"/> * * author Rob Harrop * author Adrian Colyer * author Juergen Hoeller * since 2.0 */public class AopNamespaceHandler extends NamespaceHandlerSupport /* * Register the link BeanDefinitionParser BeanDefinitionParsers for the * code config, code spring-configured, code aspectj-autoproxy * and code scoped-proxy tags. */ Override public void init() / In 2.0 XSD as well as in 2.1 XSD. registerBeanDefinitionParser(config, new ConfigBeanDefinitionParser(); registerBeanDefinitionParser(aspectj-autoproxy, new AspectJAutoProxyBeanDefinitionParser(); registerBeanDefinitionDecorator(scoped-proxy, new ScopedProxyBeanDefinitionDecorator(); / Only in 2.0 XSD: moved to context namespace as of 2.1 registerBeanDefinitionParser(spring-configured, new SpringConfiguredBeanDefinitionParser(); 根据注释，该类是aop命名空间的处理类。 利用BeanDefinitionParser解析aop:config标签，该标签包括pointcut、advisor、aspect标签。 pointcut标签允许创建AspectJExpressionPointcut，利用简单的语法： 1使用advisor标签能够配置org.springframework.aop.Advisor，并且能自动应用的bean对象中。 advisor标签支持内联定义的或者引用的org.springframework.aop.Pointcut Pointcuts： 再看AopNamespaceHandler的类结构图： image接口NamespaceHandler先上源码：package org.springframework.beans.factory.xml;import org.w3c.dom.Element;import org.w3c.dom.Node;import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.beans.factory.config.BeanDefinitionHolder;/* * Base interface used by the link DefaultBeanDefinitionDocumentReader * for handling custom namespaces in a Spring XML configuration file. * * Implementations are expected to return implementations of the * link BeanDefinitionParser interface for custom top-level tags and * implementations of the link BeanDefinitionDecorator interface for * custom nested tags. * * The parser will call link #parse when it encounters a custom tag * directly under the code <beans> tags and link #decorate when * it encounters a custom tag directly under a code <bean> tag. * * Developers writing their own custom element extensions typically will * not implement this interface directly, but rather make use of the provided * link NamespaceHandlerSupport class. * * author Rob Harrop * author Erik Wiersma * since 2.0 * see DefaultBeanDefinitionDocumentReader * see NamespaceHandlerResolver */public interface NamespaceHandler /* * Invoked by the link DefaultBeanDefinitionDocumentReader after * construction but before any custom elements are parsed. * see NamespaceHandlerSupport#registerBeanDefinitionParser(String, BeanDefinitionParser) */ void init(); /* * Parse the specified link Element and register any resulting * link BeanDefinition BeanDefinitions with the * link org.springframework.beans.factory.support.BeanDefinitionRegistry * that is embedded in the supplied link ParserContext. * Implementations should return the primary code BeanDefinition * that results from the parse phase if they wish to be used nested * inside (for example) a code <property> tag. * Implementations may return code null if they will * not be used in a nested scenario. * param element the element that is to be parsed into one or more code BeanDefinitions * param parserContext the object encapsulating the current state of the parsing process * return the primary code BeanDefinition (can be code null as explained above) */ BeanDefinition parse(Element element, ParserContext parserContext); /* * Parse the specified link Node and decorate the supplied * link BeanDefinitionHolder, returning the decorated definition. * The link Node may be either an link org.w3c.dom.Attr or an * link Element, depending on whether a custom attribute or element * is being parsed. * Implementations may choose to return a completely new definition, * which will replace the original definition in the resulting * link org.springframework.beans.factory.BeanFactory. * The supplied link ParserContext can be used to register any * additional beans needed to support the main definition. * param source the source element or attribute that is to be parsed * param definition the current bean definition * param parserContext the object encapsulating the current state of the parsing process * return the decorated definition (to be registered in the BeanFactory), * or simply the original bean definition if no decoration is required. * A code null value is strictly speaking invalid, but will be leniently * treated like the case where the original bean definition gets returned. */ BeanDefinitionHolder decorate(Node source, BeanDefinitionHolder definition, ParserContext parserContext);该接口是供处理spring的xml配置文件类DefaultBeanDefinitionDocumentReader使用的基接口。 实现类需要返回顶级标签和BeanDefinitionDecorator定义的内嵌标签的实现。 该解析器在遇到自定义的bean标签时会调用parse()和decorate()方法.抽象类NamespaceHandlerSupport源码如下：package org.springframework.beans.factory.xml;import java.util.HashMap;import java.util.Map;import org.w3c.dom.Attr;import org.w3c.dom.Element;import org.w3c.dom.Node;import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.beans.factory.config.BeanDefinitionHolder;/* * 实现了NamespaceHandlers的支持类，通过BeanDefinitionParser和BeanDefinitionDecorator的策略接口解析和装饰 * 提供了相应的方法注册解析器去处理具体的元素 */public abstract class NamespaceHandlerSupport implements NamespaceHandler /* * 保存BeanDefinitionParser的实现 */ private final Map parsers = new HashMap(); /* * 保存BeanDefinitionDecorator的实现 */ private final Map decorators = new HashMap(); /* * 根据属性保存BeanDefinitionDecorator的实现 */ private final Map attributeDecorators = new HashMap(); /* * 解析Element元素并注册 */ Override public BeanDefinition parse(Element element, ParserContext parserContext) return findParserForElement(element, parserContext).parse(element, parserContext); /* * 根据Element查找注册的BeanDefinitionParser */ private BeanDefinitionParser findParserForElement(Element element, ParserContext parserContext) String localName = parserContext.getDelegate().getLocalName(element); BeanDefinitionParser parser = sers.get(localName); if (parser = null) parserContext.getReaderContext().fatal( Cannot locate BeanDefinitionParser for element + localName + , element); return parser; /* * 装饰代理的BeanDefinitionDecorator，被注册用来处理Node */ Override public BeanDefinitionHolder decorate( Node node, BeanDefinitionHolder definition, ParserContext parserContext) return findDecoratorForNode(node, parserContext).decorate(node, definition, parserContext); /* * 从注册的实现类找出BeanDefinitionParser，支持Element(s)和Attr(s) */ private BeanDefinitionDecorator findDecoratorForNode(Node node, ParserContext parserContext) BeanDefinitionDecorator decorator = null; String localName = parserContext.getDelegate().getLocalName(node); if (node instanceof Element) decorator = this.decorators.get(localName); else if (node instanceof Attr) decorator = this.attributeDecorators.get(localName); else parserContext.getReaderContext().fatal( Cannot decorate based on Nodes of type + node.getClass().getName() + , node); if (decorator = null) parserContext.getReaderContext().fatal(Cannot locate BeanDefinitionDecorator for + (node instanceof Element ? element : attribute) + + localName + , node); return decorator; /* * 子类调用注册BeanDefinitionParser来处理具体的元素 */ protected final void registerBeanDefinitionParser(String elementName, BeanDefinitionParser parser) this.parsers.put(elementName, parser); /* * 子类调用注册BeanDefinitionDecorator来处理具体的元素 */ protected final void registerBeanDefinitionDecorator(String elementName, BeanDefinitionDecorator dec) this.decorators.put(elementName, dec); /* * 子类调用注册BeanDefinitionDecorator处理具体的属性 */ protected final void registerBeanDefinitionDecoratorForAttribute(String attrName, BeanDefinitionDecorator dec) this.attributeDecorators.put(attrName, dec); AopNamespaceHandler.init()回看AopNamespaceHandler.init()的方法体： 先从解析config元素开始：registerBeanDefinitionParser(config, new ConfigBeanDefinitionParser();1注册BeanDefinitionParser解析器，会自动调用该解析器(ConfigBeanDefinitionParser)的parse方法： /利用内嵌在ParserContext里的BeanDefinition进行注册并解析具体的元素 Override public BeanDefinition parse(Element element, ParserContext parserContext) /从parserContext里获取复合的组件定义 CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), parserContext.extractSource(element); parserContext.pushContainingComponent(compositeDef); /自动代理创建者所需的配置，用于支持通过标签创建的BeanDefinitions /当proxy-target-class=true，将强制进行类的代理 configureAutoProxyCreator(parserContext, element); List childElts = DomUtils.getChildElements(element); for (Element elt: childElts) String localName = parserContext.getDelegate().getLocalName(elt); if (POINTCUT.equals(localName) /解析提供的pointcut并利用BeanDefinitionRegistry注册 parsePointcut(elt, parserContext); else if (ADVISOR.equals(localName) parseAdvisor(elt, parserContext); else if (ASPECT.equals(localName) parseAspect(elt, parserContext); parserContext.popAndRegisterContainingComponent(); return null; 接下来我们看看parsePointcut完成了哪些事情： /* * Parses the supplied code <pointcut> and registers the resulting * Pointcut with the BeanDefinitionRegistry. */ private AbstractBeanDefinition parsePointcut(Element pointcutElement, ParserContext parserContext) String id = pointcutElement.getAttribute(ID); String expression = pointcutElement.getAttribute(EXPRESSION); AbstractBeanDefinition pointcutDefinition = null; try this.parseState.push(new PointcutEntry(id); /AspectJExpressionPointcut使用给定的表达式创建BeanDefinition pointcutDefinition = createPointcutDefinition(expression); pointcutDefinition.setSource(parserContext.extractSource(pointcutElement); String pointcutBeanName = id; /进行注册,切点名称为空时，自动生成 if (StringUtils.hasText(pointcutBeanName) parserContext.getRegistry().registerBeanDefinition(pointcutBeanName, pointcutDefinition); else pointcutBeanName = parserContext.getReaderContext().registerWithGeneratedName(pointcutDefinition); /注册切点组件 parserContext.registerComponent( new PointcutComponentDefinition(pointcutBeanName, pointcutDefinition, expression); finally this.parseState.pop(); return pointcutDefinition; 后面parseAdvisor、parseAspect也是对不同的元素进行注册，具体代码如下： /* * Parses the supplied code <advisor> element and registers the resulting * link org.springframework.aop.Advisor and any resulting link org.springframework.aop.Pointcut * with the supplied link BeanDefinitionRegistry. */ private void parseAdvisor(Element advisorElement, ParserContext parserContext) AbstractBeanDefinition advisorDef = createAdvisorBeanDefinition(advisorElement, parserContext); String id = advisorElement.getAttribute(ID); try this.parseState.push(new AdvisorEntry(id); String advisorBeanName = id; if (StringUtils.hasText(advisorBeanName) parserContext.getRegistry().registerBeanDefinition(advisorBeanName, advisorDef); else advisorBeanName = parserContext.getReaderContext().registerWithGeneratedName(advisorDef); Object pointcut = parsePointcutProperty(advisorElement, parserContext); if (pointcut instanceof BeanDefinition) advisorDef.getPropertyValues().add(POINTCUT, pointcut); parserContext.registerComponent( new AdvisorComponentDefinition(advisorBeanName, advisorDef, (BeanDefinition) pointcut); else if (pointcut instanceof String) advisorDef.getPropertyValues().add(POINTCUT, new RuntimeBeanReference(String) pointcut); parserContext.registerComponent( new AdvisorComponentDefinition(advisorBeanName, advisorDef); finally this.parseState.pop(); private void parseAspect(Element aspectElement, ParserContext parserContext) String aspectId = aspectElement.getAttribute(ID); String aspectName = aspectElement.getAttribute(REF); try this.parseState.push(new AspectEntry(aspectId, aspectName); List beanDefinitions = new ArrayList(); List beanReferences = new ArrayList(); List declareParents = DomUtils.getChildElementsByTagName(aspectElement, DECLARE_PARENTS); for (int i = METHOD_INDEX; i declareParents.size(); i+) Element declareParentsElement = declareParents.get(i); beanDefinitions.add(parseDeclareParents(declareParentsElement, parserContext); / We have to parse advice and all the advice kinds in one loop, to get the / ordering semantics right. NodeList nodeList = aspectElement.getChildNodes(); boolean adviceFoundAlready = false; for (int i = 0; i nodeList.getLength(); i+) Node node = nodeList.item(i); if (isAdviceNode(node, parserContext) if (!adviceFoundAlready) adviceFoundAlready = true; if (!StringUtils.hasText(aspectName) parserContext.getReaderContext().error( tag needs aspect bean reference via ref attribute when declaring advices., aspectElement, this.parseState.snapshot(); return; beanReferences.add(new RuntimeBeanReference(aspectName); Abstr