阅读本文请先稍微浏览下上篇文章Spring源码情操陶冶-AOP之ConfigBeanDefinitionParser解析器，本文则对aop模式的通知类作简单的分析
入口
根据前文讲解，我们知道通知类的解析主要建立在aop:aspect节点的解析上。废话少说我们直接观察ConfigBeanDefinitionParser#parseAdvice()方法
ConfigBeanDefinitionParser#parseAdvice()-解析通知类并注册到bean工厂
先奉上源码
/**
* Parses one of '{@code before}', '{@code after}', '{@code after-returning}',
* '{@code after-throwing}' or '{@code around}' and registers the resulting
* BeanDefinition with the supplied BeanDefinitionRegistry.
* @return the generated advice RootBeanDefinition
*/
/**
** 这稍微对入参作下备注
** @param aspectName 待绑定的切面名
** @param order 排序号
** @param aspectElement <aop:aspect>节点
** @param adviceElement <aop:advice>节点
** @param parserContext 解析节点的上下文对象
** @param beanDefinitions 与aspect相关的所有bean对象集合
** @param beanReferences 与aspect相关的所有bean引用对象集合
**/
private AbstractBeanDefinition parseAdvice(
String aspectName, int order, Element aspectElement, Element adviceElement, ParserContext parserContext,
List<BeanDefinition> beanDefinitions, List<BeanReference> beanReferences) {
try {
this.parseState.push(new AdviceEntry(parserContext.getDelegate().getLocalName(adviceElement)));
// create the method factory bean
// 解析advice节点中的"method"属性，并包装为MethodLocatingFactoryBean对象
RootBeanDefinition methodDefinition = new RootBeanDefinition(MethodLocatingFactoryBean.class);
methodDefinition.getPropertyValues().add("targetBeanName", aspectName);
methodDefinition.getPropertyValues().add("methodName", adviceElement.getAttribute("method"));
methodDefinition.setSynthetic(true);
// create instance factory definition
// 关联aspectName，包装为SimpleBeanFactoryAwareAspectInstanceFactory对象
RootBeanDefinition aspectFactoryDef =
new RootBeanDefinition(SimpleBeanFactoryAwareAspectInstanceFactory.class);
aspectFactoryDef.getPropertyValues().add("aspectBeanName", aspectName);
aspectFactoryDef.setSynthetic(true);
// register the pointcut
// 涉及point-cut属性的解析，并结合上述的两个bean最终包装为AbstractAspectJAdvice通知对象
AbstractBeanDefinition adviceDef = createAdviceDefinition(
adviceElement, parserContext, aspectName, order, methodDefinition, aspectFactoryDef,
beanDefinitions, beanReferences);
// configure the advisor，最终包装为AspectJPointcutAdvisor对象
RootBeanDefinition advisorDefinition = new RootBeanDefinition(AspectJPointcutAdvisor.class);
advisorDefinition.setSource(parserContext.extractSource(adviceElement));
advisorDefinition.getConstructorArgumentValues().addGenericArgumentValue(adviceDef);
if (aspectElement.hasAttribute(ORDER_PROPERTY)) {
advisorDefinition.getPropertyValues().add(
ORDER_PROPERTY, aspectElement.getAttribute(ORDER_PROPERTY));
}
// register the final advisor
parserContext.getReaderContext().registerWithGeneratedName(advisorDefinition);
return advisorDefinition;
}
finally {
this.parseState.pop();
}
}
由代码可知，最终解析得到的bean对象为AspectJPointcutAdvisor.class类型的，其内部拥有Advice的接口对象属性，而具体的解析则需要查看ConfigBeanDefinitionParser#createAdviceDefinition()方法。
ConfigBeanDefinitionParser#createAdviceDefinition()-具体解析通知类
源码奉上
/**
* Creates the RootBeanDefinition for a POJO advice bean. Also causes pointcut
* parsing to occur so that the pointcut may be associate with the advice bean.
* This same pointcut is also configured as the pointcut for the enclosing
* Advisor definition using the supplied MutablePropertyValues.
*/
private AbstractBeanDefinition createAdviceDefinition(
Element adviceElement, ParserContext parserContext, String aspectName, int order,
RootBeanDefinition methodDef, RootBeanDefinition aspectFactoryDef,
List<BeanDefinition> beanDefinitions, List<BeanReference> beanReferences) {
// 首先根据adviceElement节点分析出是什么类型的Advice。
RootBeanDefinition adviceDefinition = new RootBeanDefinition(getAdviceClass(adviceElement, parserContext));
adviceDefinition.setSource(parserContext.extractSource(adviceElement));
// 设置aspectName属性和declarationOrder属性
adviceDefinition.getPropertyValues().add(ASPECT_NAME_PROPERTY, aspectName);
adviceDefinition.getPropertyValues().add(DECLARATION_ORDER_PROPERTY, order);
// 解析节点是否含有`returning`/`throwing`/`arg-names`，有则设置
if (adviceElement.hasAttribute(RETURNING)) {
adviceDefinition.getPropertyValues().add(
RETURNING_PROPERTY, adviceElement.getAttribute(RETURNING));
}
if (adviceElement.hasAttribute(THROWING)) {
adviceDefinition.getPropertyValues().add(
THROWING_PROPERTY, adviceElement.getAttribute(THROWING));
}
if (adviceElement.hasAttribute(ARG_NAMES)) {
adviceDefinition.getPropertyValues().add(
ARG_NAMES_PROPERTY, adviceElement.getAttribute(ARG_NAMES));
}
// 设置构造函数的入参变量
// Method/AspectJExpressionPointcut/AspectInstanceFactory三个入参
ConstructorArgumentValues cav = adviceDefinition.getConstructorArgumentValues();
cav.addIndexedArgumentValue(METHOD_INDEX, methodDef);
// 解析point-cut属性
Object pointcut = parsePointcutProperty(adviceElement, parserContext);
if (pointcut instanceof BeanDefinition) {
cav.addIndexedArgumentValue(POINTCUT_INDEX, pointcut);
beanDefinitions.add((BeanDefinition) pointcut);
}
else if (pointcut instanceof String) {
RuntimeBeanReference pointcutRef = new RuntimeBeanReference((String) pointcut);
cav.addIndexedArgumentValue(POINTCUT_INDEX, pointcutRef);
beanReferences.add(pointcutRef);
}
cav.addIndexedArgumentValue(ASPECT_INSTANCE_FACTORY_INDEX, aspectFactoryDef);
return adviceDefinition;
}
Advice接口类与节点对应关系如下，其均是AbstractAspectJAdvice.class的子类
aop:before对应AspectJMethodBeforeAdvice.classaop:after对应AspectJAfterAdvice.classaop:after-returning对应AspectJAfterReturningAdvice.classaop:after-throwing对应AspectJAfterThrowingAdvice.classaop:around对应AspectJAroundAdvice.class
通知类生成的bean对象，其会设置
aspectName切面名、declarationOrder序列等属性；且对其公共构造函数三个入参Method/AspectJExpressionPointcut/AspectInstanceFactory都会进行设置
parseAdvice()最主要的目的是使aspect对象中的方法与通知类结合起来，从而起到多样化的作用，下面的简单实例就是如此
例子结尾
public class TestAdvice {
/**
* 在核心业务执行前执行，不能阻止核心业务的调用。
* @param joinPoint
*/
private void doBefore(JoinPoint joinPoint) {
System.out.println("-----doBefore().invoke-----");
System.out.println(" 此处意在执行核心业务逻辑前，做一些安全性的判断等等");
System.out.println(" 可通过joinPoint来获取所需要的内容");
System.out.println("-----End of doBefore()------");
}
/**
* 手动控制调用核心业务逻辑，以及调用前和调用后的处理,
*
* 注意：当核心业务抛异常后，立即退出，转向After Advice
* 执行完毕After Advice，再转到Throwing Advice
* @param pjp
* @return
* @throws Throwable
*/
private Object doAround(ProceedingJoinPoint pjp) throws Throwable {
System.out.println("-----doAround().invoke-----");
System.out.println(" 此处可以做类似于Before Advice的事情");
//调用核心逻辑
Object retVal = pjp.proceed();
System.out.println(" 此处可以做类似于After Advice的事情");
System.out.println("-----End of doAround()------");
return retVal;
}
/**
* 核心业务逻辑退出后（包括正常执行结束和异常退出），执行此Advice
* @param joinPoint
*/
private void doAfter(JoinPoint joinPoint) {
System.out.println("-----doAfter().invoke-----");
System.out.println(" 此处意在执行核心业务逻辑之后，做一些日志记录操作等等");
System.out.println(" 可通过joinPoint来获取所需要的内容");
System.out.println("-----End of doAfter()------");
}
/**
* 核心业务逻辑调用正常退出后，不管是否有返回值，正常退出后，均执行此Advice
* @param joinPoint
*/
private void doReturn(JoinPoint joinPoint) {
System.out.println("-----doReturn().invoke-----");
System.out.println(" 此处可以对返回值做进一步处理");
System.out.println(" 可通过joinPoint来获取所需要的内容");
System.out.println("-----End of doReturn()------");
}
/**
* 核心业务逻辑调用异常退出后，执行此Advice，处理错误信息
* @param joinPoint
* @param ex
*/
private void doThrowing(JoinPoint joinPoint,Throwable ex) {
System.out.println("-----doThrowing().invoke-----");
System.out.println(" 错误信息："+ex.getMessage());
System.out.println(" 此处意在执行核心业务逻辑出错时，捕获异常，并可做一些日志记录操作等等");
System.out.println(" 可通过joinPoint来获取所需要的内容");
System.out.println("-----End of doThrowing()------");
}
}
对应的spring配置如下
<bean id="xmlHandler" class="com.jing.aop.TestAdvice" />
<aop:config>
<aop:aspect id="aspect" ref="xmlHandler">
<aop:pointcut id="pointUserMgr" expression="execution(* com.tgb.aop.*.find*(..))"/>
<aop:before method="doBefore" pointcut-ref="pointUserMgr"/>
<aop:after method="doAfter" pointcut-ref="pointUserMgr"/>
<aop:around method="doAround" pointcut-ref="pointUserMgr"/>
<aop:after-returning method="doReturn" pointcut-ref="pointUserMgr"/>
<aop:after-throwing method="doThrowing" throwing="ex" pointcut-ref="pointUserMgr"/>
</aop:aspect>
</aop:config>
具体的如何触发相应的Advice我们放在后续的篇章讲解，敬请期待