<aop:config> 标签的解析：
<bean id="loggingAspect" class="com.zhuguang.jack.aop.aspect.AspectXml1"></bean>
<aop:config>
<aop:pointcut id="pointcut" expression="execution(* com.zhuguang.jack.aop.aspect.AspectXml1.*(..))" />
<aop:aspect ref="loggingAspect" order="1" >
<aop:before method="before" pointcut-ref="pointcut"/>
<aop:after method="after" pointcut-ref="pointcut"/>
<aop:after-returning method="afterReturning" pointcut-ref="pointcut" returning="result"/>
<aop:after-throwing method="afterThrowing" pointcut-ref="pointcut" throwing="exception"/>
</aop:aspect>
</aop:config>
aop:config对应的类是AspectJAwareAdvisorAutoProxyCreator。加到bean工厂。
aop:aspect 不用解析成类。
aop:before 对应的类是AspectJPointcutAdvisor，里面有AspectJMethodBeforeAdvice，里面有MethodLocatingFactoryBean和SimpleBeanFactoryAwareAspectInstanceFactory和pointcut。加到bean工厂。
aop:after ，aop:after-returning，aop:after-throwing与aop:before类似。
类的属性值就是根据标签上面写的解析出来的。
解析自定义标签就是创建bean的定义，<aop:before，<aop:after，<aop:after-returning，<aop:after-throwing。分别对应AspectJMethodBeforeAdvice.class;AspectJAfterAdvice.class;AspectJAfterReturningAdvice.class;AspectJAfterThrowingAdvice.class;AspectJAroundAdvice.class;
AspectJAwareAdvisorAutoProxyCreator是支持AOP功能的入口类，必定实现BeanPostProcessor接口，bean实例化的时候就回去调用这个类，就会找这个类有没有切面，有切面就生成代理，
首先找到AopNamespaceHandler，然后找到registerBeanDefinitionParser("config", new ConfigBeanDefinitionParser());
public class AopNamespaceHandler extends NamespaceHandlerSupport {
@Override
public void init() {
registerBeanDefinitionParser("config", new ConfigBeanDefinitionParser());
registerBeanDefinitionParser("aspectj-autoproxy", new AspectJAutoProxyBeanDefinitionParser());
registerBeanDefinitionDecorator("scoped-proxy", new ScopedProxyBeanDefinitionDecorator());
registerBeanDefinitionParser("spring-configured", new SpringConfiguredBeanDefinitionParser());
}
}
ConfigBeanDefinitionParser类里面有一个解析标签的方法parse()，
public BeanDefinition parse(Element element, ParserContext parserContext) { //element = [aop:config: null]，parserContext = org.springframework.beans.factory.xml.ParserContext@2fd953a6，
CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), parserContext.extractSource(element));
parserContext.pushContainingComponent(compositeDef);
configureAutoProxyCreator(parserContext, element); //ParserContext里面有一个属性XmlReaderContext readerContext，BeanDefinitionParserDelegate delegate，解析这个元素就是为了创建BeanDefinition对象，创建AspectJAwareAdvisorAutoProxyCreator的bean定义并且加载到bean工厂。这个类实现了BeanPostProcessor接口，实例化任何一个bean的时候，会调用spring容器中所有BeanPostProcessor接口的类的方法，AspectJAwareAdvisorAutoProxyCreator就会去检测要实例化的这个bean有没有切面，有切面，就帮这个bean生成代理，
List<Element> childElts = DomUtils.getChildElements(element); //[[aop:pointcut], [aop:advisor]]子标签，
for (Element elt: childElts) {
String localName = parserContext.getDelegate().getLocalName(elt); //aop下面就3个标签，
if (POINTCUT.equals(localName)) {
parsePointcut(elt, parserContext);
}
else if (ADVISOR.equals(localName)) {
parseAdvisor(elt, parserContext);
}
else if (ASPECT.equals(localName)) {
parseAspect(elt, parserContext);
}
}
parserContext.popAndRegisterContainingComponent();
return null;
}
private void configureAutoProxyCreator(ParserContext parserContext, Element element) {
AopNamespaceUtils.registerAspectJAutoProxyCreatorIfNecessary(parserContext, element);
}
public static void registerAspectJAutoProxyCreatorIfNecessary(ParserContext parserContext, Element sourceElement) {
BeanDefinition beanDefinition = AopConfigUtils.registerAspectJAutoProxyCreatorIfNecessary(
parserContext.getRegistry(), parserContext.extractSource(sourceElement)); //创建beanDefinition 对象，返回AspectJAwareAdvisorAutoProxyCreator的bean的定义，
useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement);
registerComponentIfNecessary(beanDefinition, parserContext);
}
public static BeanDefinition registerAspectJAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
return registerOrEscalateApcAsRequired(AspectJAwareAdvisorAutoProxyCreator.class, registry, source); //注册器是DefaultListableBeanFactory，null，
}
private static BeanDefinition registerOrEscalateApcAsRequired(Class<?> cls, BeanDefinitionRegistry registry, Object source) { //AspectJAwareAdvisorAutoProxyCreator，bean工厂，null，
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) { //看bean工厂中有没有AspectJAwareAdvisorAutoProxyCreator的实例，名字是internalAutoProxyCreator，有就直接返回，没有就在bean工厂创建AspectJAwareAdvisorAutoProxyCreator的实例，名字叫做internalAutoProxyCreator。
BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
if (!cls.getName().equals(apcDefinition.getBeanClassName())) {
int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName());
int requiredPriority = findPriorityForClass(cls);
if (currentPriority < requiredPriority) {
apcDefinition.setBeanClassName(cls.getName());
}
}
return null;
}
RootBeanDefinition beanDefinition = new RootBeanDefinition(cls); //创建AspectJAwareAdvisorAutoProxyCreator的实例
beanDefinition.setSource(source);
beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE);
beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition); //加到bean工厂，名字叫做internalAutoProxyCreator，
return beanDefinition;
}
private static void useClassProxyingIfNecessary(BeanDefinitionRegistry registry, Element sourceElement) {
if (sourceElement != null) {
boolean proxyTargetClass = Boolean.valueOf(sourceElement.getAttribute(PROXY_TARGET_CLASS_ATTRIBUTE)); //获取[aop:config]标签的proxy-target-class="false"属性，true就是cglib的动态代理，faslse就是jdk的动态代理，没有写就是jdk的动态代理，
if (proxyTargetClass) {//true
AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
}
boolean exposeProxy = Boolean.valueOf(sourceElement.getAttribute(EXPOSE_PROXY_ATTRIBUTE)); //sourceElement = [aop:config]标签，
if (exposeProxy) {
AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);
}
}
}
public static void forceAutoProxyCreatorToUseClassProxying(BeanDefinitionRegistry registry) {
if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
BeanDefinition definition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
definition.getPropertyValues().add("proxyTargetClass", Boolean.TRUE); //往internalAutoProxyCreator的bean定义里面加了一个属性，
}
}
private static void registerComponentIfNecessary(BeanDefinition beanDefinition, ParserContext parserContext) { //AspectJAwareAdvisorAutoProxyCreator的bean定义，org.springframework.beans.factory.xml.ParserContext@2fd953a6，
if (beanDefinition != null) {
BeanComponentDefinition componentDefinition = new BeanComponentDefinition(beanDefinition, AopConfigUtils.AUTO_PROXY_CREATOR_BEAN_NAME); //把AspectJAwareAdvisorAutoProxyCreator的bean定义包装成BeanComponentDefinition，包装的名称叫做internalAutoProxyCreator，
parserContext.registerComponent(componentDefinition);
}
}
BeanComponentDefinition extends BeanDefinitionHolder。
BeanDefinition最终会包装成BeanDefinitionHolder，BeanDefinitionHolder有BeanDefinition beanDefinition是bean的定义和String beanName 是bean的名称。
private void parseAspect(Element aspectElement, ParserContext parserContext) { //解析<aop:aspect标签，
String aspectId = aspectElement.getAttribute(ID); //id属性，
String aspectName = aspectElement.getAttribute(REF); //ref是对应的切面类，
try {
this.parseState.push(new AspectEntry(aspectId, aspectName));
List<BeanDefinition> beanDefinitions = new ArrayList<BeanDefinition>();
List<BeanReference> beanReferences = new ArrayList<BeanReference>();
List<Element> 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));
}
NodeList nodeList = aspectElement.getChildNodes();//aspect的子元素，<aop:before，<aop:after，<aop:after-returning，<aop:after-throwing。
boolean adviceFoundAlready = false;
for (int i = 0; i < nodeList.getLength(); i++) {
Node node = nodeList.item(i); //<aop:before，<aop:after，<aop:after-returning，<aop:after-throwing。
if (isAdviceNode(node, parserContext)) {
if (!adviceFoundAlready) {
adviceFoundAlready = true;
beanReferences.add(new RuntimeBeanReference(aspectName));
}
AbstractBeanDefinition advisorDefinition = parseAdvice(aspectName, i, aspectElement, (Element) node, parserContext, beanDefinitions, beanReferences); //解析通知节点<aop:before，<aop:after，<aop:after-returning，<aop:after-throwing标签。目的也是为了创建BeanDefinition。
//返回AspectJPointcutAdvisor的bean定义，constructorArgumentValues属性里面的gebericArgumentValues里面有AspectJMethodBeforeAdvice（现在解析的是aop:before标签）（还有after,around,throw,exception几种）的bean定义里面的constructorArgumentValues属性里面有MethodLocatingFactoryBean的bean定义和SimpleBeanFactoryAwareAspectInstanceFactory的bean定义和pointcut。
beanDefinitions.add(advisorDefinition);//4种前置后置环绕等通知加进去，一个是before标签的bean定义，一个是after的bean定义，一个是afterReturn的bean定义，一个是afterThrow的bean定义。
}
}
//解析aop:aspect标签，就是把里面的aop：before，aop:after，aop:afterthrow，aop:afterRuturnning，这几种标签解析成bean的定义，跟需要加入切面的类还没有建立直接的关系。
AspectComponentDefinition aspectComponentDefinition = createAspectComponentDefinition(
aspectElement, aspectId, beanDefinitions, beanReferences, parserContext);
parserContext.pushContainingComponent(aspectComponentDefinition);
List<Element> pointcuts = DomUtils.getChildElementsByTagName(aspectElement, POINTCUT); //这个<aop:aspect 标签里面的pointcut标签，
for (Element pointcutElement : pointcuts) {
parsePointcut(pointcutElement, parserContext);
}
parserContext.popAndRegisterContainingComponent();
}
finally {
this.parseState.pop();
}
}
private AbstractBeanDefinition parseAdvice(String aspectName, int order, Element aspectElement, Element adviceElement, ParserContext parserContext,List<BeanDefinition> beanDefinitions, List<BeanReference> beanReferences) {//aspectName = aop:aspect标签的ref属性的值，aspectElement = [aop:aspect: null]标签，adviceElement = <aop:before，<aop:after，<aop:after-returning，<aop:after-throwing。
try {
this.parseState.push(new AdviceEntry(parserContext.getDelegate().getLocalName(adviceElement)));
RootBeanDefinition methodDefinition = new RootBeanDefinition(MethodLocatingFactoryBean.class); //创建这个的bean定义，
methodDefinition.getPropertyValues().add("targetBeanName", aspectName);//loggingAspect，切面类名称。
methodDefinition.getPropertyValues().add("methodName", adviceElement.getAttribute("method")); //执行的方法，
methodDefinition.setSynthetic(true);
RootBeanDefinition aspectFactoryDef = new RootBeanDefinition(SimpleBeanFactoryAwareAspectInstanceFactory.class); //创建这个的bean定义，
aspectFactoryDef.getPropertyValues().add("aspectBeanName", aspectName);//loggingAspect，切面类名称。
aspectFactoryDef.setSynthetic(true);
AbstractBeanDefinition adviceDef = createAdviceDefinition(adviceElement, parserContext, aspectName, order, methodDefinition, aspectFactoryDef,beanDefinitions, beanReferences); //返回AspectJMethodBeforeAdvice的bean定义constructorArgumentValues属性里面有MethodLocatingFactoryBean的bean定义和SimpleBeanFactoryAwareAspectInstanceFactory的bean定义和pointcut，前置通知的beanDefinition（<aop:before>标签的beanDefinition）。
// configure the advisor
RootBeanDefinition advisorDefinition = new RootBeanDefinition(AspectJPointcutAdvisor.class); //切面内
advisorDefinition.setSource(parserContext.extractSource(adviceElement)); //[aop:before: null]，
advisorDefinition.getConstructorArgumentValues().addGenericArgumentValue(adviceDef); //切面里面必须要有advice，通过构造函数设置值。
if (aspectElement.hasAttribute(ORDER_PROPERTY)) {
advisorDefinition.getPropertyValues().add(ORDER_PROPERTY, aspectElement.getAttribute(ORDER_PROPERTY));
}
// register the final advisor
parserContext.getReaderContext().registerWithGeneratedName(advisorDefinition);
return advisorDefinition;//返回这个切面。AspectJPointcutAdvisor的bean定义，constructorArgumentValues属性里面的gebericArgumentValues属性里面有AspectJMethodBeforeAdvice的bean定义里面的constructorArgumentValues属性里面有MethodLocatingFactoryBean的bean定义和SimpleBeanFactoryAwareAspectInstanceFactory的bean定义和pointcut。
}
finally {
this.parseState.pop();
}
}
private AbstractBeanDefinition createAdviceDefinition(
Element adviceElement, ParserContext parserContext, String aspectName, int order,
RootBeanDefinition methodDef, RootBeanDefinition aspectFactoryDef,
List<BeanDefinition> beanDefinitions, List<BeanReference> beanReferences) {
RootBeanDefinition adviceDefinition = new RootBeanDefinition(getAdviceClass(adviceElement, parserContext)); //AspectJMethodBeforeAdvice的bean定义，before的类是AspectJMethodBeforeAdvice，after的类是AspectJAfterAdvice，return的类是AspectJAfterReturningAdvice，afterThrowing的类是AspectJAfterThrowingAdvice，around的类是AspectJAroundAdvice。
adviceDefinition.setSource(parserContext.extractSource(adviceElement));
adviceDefinition.getPropertyValues().add(ASPECT_NAME_PROPERTY, aspectName); //切面类名称
adviceDefinition.getPropertyValues().add(DECLARATION_ORDER_PROPERTY, order);
if (adviceElement.hasAttribute(RETURNING)) {//添加属性
adviceDefinition.getPropertyValues().add(
RETURNING_PROPERTY, adviceElement.getAttribute(RETURNING));
}
if (adviceElement.hasAttribute(THROWING)) {//添加属性
adviceDefinition.getPropertyValues().add(
THROWING_PROPERTY, adviceElement.getAttribute(THROWING));
}
if (adviceElement.hasAttribute(ARG_NAMES)) {//添加属性
adviceDefinition.getPropertyValues().add(
ARG_NAMES_PROPERTY, adviceElement.getAttribute(ARG_NAMES));
}
ConstructorArgumentValues cav = adviceDefinition.getConstructorArgumentValues(); //构造函数参数。
cav.addIndexedArgumentValue(METHOD_INDEX, methodDef);
Object pointcut = parsePointcutProperty(adviceElement, parserContext); //解析pointcut，
if (pointcut instanceof BeanDefinition) {//有pointcut属性，返回bean定义，
cav.addIndexedArgumentValue(POINTCUT_INDEX, pointcut);
beanDefinitions.add((BeanDefinition) pointcut);
}
else if (pointcut instanceof String) {//有pointcut-ref属性，返回字符串，
RuntimeBeanReference pointcutRef = new RuntimeBeanReference((String) pointcut);
cav.addIndexedArgumentValue(POINTCUT_INDEX, pointcutRef);
beanReferences.add(pointcutRef);
}
cav.addIndexedArgumentValue(ASPECT_INSTANCE_FACTORY_INDEX, aspectFactoryDef);
return adviceDefinition; //返回AspectJMethodBeforeAdvice的bean定义里面有MethodLocatingFactoryBean的bean定义和SimpleBeanFactoryAwareAspectInstanceFactory的bean定义和pointcut。
}
private Class<?> getAdviceClass(Element adviceElement, ParserContext parserContext) {
String elementName = parserContext.getDelegate().getLocalName(adviceElement);
if (BEFORE.equals(elementName)) {//前置通知
return AspectJMethodBeforeAdvice.class;
}
else if (AFTER.equals(elementName)) {//后置通知
return AspectJAfterAdvice.class;
}
else if (AFTER_RETURNING_ELEMENT.equals(elementName)) {//返回通知
return AspectJAfterReturningAdvice.class;
}
else if (AFTER_THROWING_ELEMENT.equals(elementName)) {//异常通知
return AspectJAfterThrowingAdvice.class;
}
else if (AROUND.equals(elementName)) {//环绕通知
return AspectJAroundAdvice.class;
}
}
private Object parsePointcutProperty(Element element, ParserContext parserContext) { //element = aop:before标签，
if (element.hasAttribute(POINTCUT) && element.hasAttribute(POINTCUT_REF)) { //没有pointcut和pointcut-ref属性，直接报错。
parserContext.getReaderContext().error("Cannot define both 'pointcut' and );
return null;
}
else if (element.hasAttribute(POINTCUT)) {
String expression = element.getAttribute(POINTCUT);
AbstractBeanDefinition pointcutDefinition = createPointcutDefinition(expression); //创建AspectJExpressionPointcut的bean定义，
pointcutDefinition.setSource(parserContext.extractSource(element));
return pointcutDefinition;
}
else if (element.hasAttribute(POINTCUT_REF)) {
String pointcutRef = element.getAttribute(POINTCUT_REF);
return pointcutRef;//返回字符串，
}
}
private AspectComponentDefinition createAspectComponentDefinition(
Element aspectElement, String aspectId, List<BeanDefinition> beanDefs,
List<BeanReference> beanRefs, ParserContext parserContext) {
BeanDefinition[] beanDefArray = beanDefs.toArray(new BeanDefinition[beanDefs.size()]); //4个前置后置环绕等通知的数组，
BeanReference[] beanRefArray = beanRefs.toArray(new BeanReference[beanRefs.size()]);
Object source = parserContext.extractSource(aspectElement);
return new AspectComponentDefinition(aspectId, beanDefArray, beanRefArray, source);
}
自定义标签都会有一个类与之对应，这个类是spring自己的类，然后加到spring的容器中，跟非自定义标签<bean>的解析类似。
<aop:config>
<aop:pointcut id="pointcut" expression="execution(* com.zhuguang.jack.aop.aspect.AspectXml1.*(..))" />
aop:pointcut 解析成AspectJExpressionPointcut类，aop:config不用解析。
类的属性值就是根据标签上面写的解析出来的。
parsePointcut(elt, parserContext); //[aop:pointcut: null]，解析pointcut标签，
private AbstractBeanDefinition parsePointcut(Element pointcutElement, ParserContext parserContext) {
String id = pointcutElement.getAttribute(ID); //pointcut
String expression = pointcutElement.getAttribute(EXPRESSION); //execution(* com.zhuguang.jack.aop.aspect.AspectXml1.*(..))，
AbstractBeanDefinition pointcutDefinition = null;
try {
this.parseState.push(new PointcutEntry(id));
pointcutDefinition = createPointcutDefinition(expression); //AspectJExpressionPointcut的bean定义，里面有point的表达式，
pointcutDefinition.setSource(parserContext.extractSource(pointcutElement));
String pointcutBeanName = id; //pointcut
if (StringUtils.hasText(pointcutBeanName)) {
parserContext.getRegistry().registerBeanDefinition(pointcutBeanName, pointcutDefinition); //加到spring的容器，名字是pointcut，bean定义是AspectJExpressionPointcut的bean定义，
}
parserContext.registerComponent(new PointcutComponentDefinition(pointcutBeanName, pointcutDefinition, expression)); //pointcut，AspectJExpressionPointcut的beanDefinition，execution(* com.zhuguang.jack.aop.aspect.AspectXml1.*(..))，加到栈中，
}
finally {
this.parseState.pop();
}
return pointcutDefinition; //返回AspectJExpressionPointcut的bean定义，
}
protected AbstractBeanDefinition createPointcutDefinition(String expression) {
RootBeanDefinition beanDefinition = new RootBeanDefinition(AspectJExpressionPointcut.class);
beanDefinition.setScope(BeanDefinition.SCOPE_PROTOTYPE);
beanDefinition.setSynthetic(true);
beanDefinition.getPropertyValues().add(EXPRESSION, expression);
return beanDefinition;
}
<aop:config proxy-target-class="false">
<aop:advisor pointcut-ref="pc" advice-ref="userTxAdvice"/>
</aop:config>
aop:advisor 对应的类是DefaultBeanFactoryPointcutAdvisor，aop:config不用解析，然后解析pointcut-ref属性和 advice-ref属性。最后加到bean容器中去。
类的属性值就是根据标签上面写的解析出来的。
private void parseAdvisor(Element advisorElement, ParserContext parserContext) { //解析Advisor标签
AbstractBeanDefinition advisorDef = createAdvisorBeanDefinition(advisorElement, parserContext); //创建bean定义对象，返回DefaultBeanFactoryPointcutAdvisor的beanDefinition，他的PropertyValues属性 = new RuntimeBeanNameReference(userTxAdvice)，userTxAdvice是需要IOC依赖注入的，
String id = advisorElement.getAttribute(ID);
try {
this.parseState.push(new AdvisorEntry(id));
String advisorBeanName = id;
if (StringUtils.hasText(advisorBeanName)) {
parserContext.getRegistry().registerBeanDefinition(advisorBeanName, advisorDef); //advisorDef 加到bean工厂中去，
}
else {
advisorBeanName = parserContext.getReaderContext().registerWithGeneratedName(advisorDef); //自动生成的名字org.springframework.aop.support.DefaultBeanFactoryPointcutAdvisor#0，advisorDef 加到bean工厂中去，
}
Object pointcut = parsePointcutProperty(advisorElement, parserContext); //解析pointcut-ref属性，
if (pointcut instanceof BeanDefinition) {//根据pointcut返回beanDefinition，根据pointcut-ref返回String，
advisorDef.getPropertyValues().add(POINTCUT, pointcut); // 添加pointcut属性，
parserContext.registerComponent(new AdvisorComponentDefinition(advisorBeanName, advisorDef, (BeanDefinition) pointcut));//注册到栈中，
}
else if (pointcut instanceof String) {
advisorDef.getPropertyValues().add(POINTCUT, new RuntimeBeanReference((String) pointcut));//将pointcut-ref转换成RuntimeBeanReference，然后添加pointcut属性，
parserContext.registerComponent(new AdvisorComponentDefinition(advisorBeanName, advisorDef));//注册到栈中，
}
}
}
private AbstractBeanDefinition createAdvisorBeanDefinition(Element advisorElement, ParserContext parserContext) { //[aop:advisor: null]标签，
RootBeanDefinition advisorDefinition = new RootBeanDefinition(DefaultBeanFactoryPointcutAdvisor.class);
advisorDefinition.setSource(parserContext.extractSource(advisorElement));
String adviceRef = advisorElement.getAttribute(ADVICE_REF); //advice-ref属性 = userTxAdvice（ref就是引用，就需要依赖注入）
if (!StringUtils.hasText(adviceRef)) {
parserContext.getReaderContext().error(pshot());
}
else {
advisorDefinition.getPropertyValues().add(ADVICE_BEAN_NAME, new RuntimeBeanNameReference(adviceRef)); //userTxAdvice封装成RuntimeBeanNameReference，ref是引用要依赖注入，当发现依赖注入的类型是RuntimeBeanNameReference的时候，那么就会去通过bean工厂去拿这个对象。
}
if (advisorElement.hasAttribute(ORDER_PROPERTY)) { //排序属性
advisorDefinition.getPropertyValues().add(
ORDER_PROPERTY, advisorElement.getAttribute(ORDER_PROPERTY));
}
return advisorDefinition;//返回DefaultBeanFactoryPointcutAdvisor的beanDefinition，他的PropertyValues属性 = new RuntimeBeanNameReference(userTxAdvice)，userTxAdvice是需要IOC依赖注入的，
}
private Object parsePointcutProperty(Element element, ParserContext parserContext) { //element = [aop:advisor: null]标签，
if (element.hasAttribute(POINTCUT) && element.hasAttribute(POINTCUT_REF)) { //是否有pointcut属性
parserContext.getReaderContext().error(ot());
return null;
}
else if (element.hasAttribute(POINTCUT)) { //pointcut属性
// Create a pointcut for the anonymous pc and register it.
String expression = element.getAttribute(POINTCUT);
AbstractBeanDefinition pointcutDefinition = createPointcutDefinition(expression); //AspectJExpressionPointcut的bean定义，
pointcutDefinition.setSource(parserContext.extractSource(element));
return pointcutDefinition;
}
else if (element.hasAttribute(POINTCUT_REF)) { //pointcut-ref属性
String pointcutRef = element.getAttribute(POINTCUT_REF); //string：引用的名字，
if (!StringUtils.hasText(pointcutRef)) {
parserContext.getReaderContext().error(ement, this.parseState.snapshot());
return null;
}
return pointcutRef; //string：引用的名字，
}
}