Spring AOP: passing target to Aspect

问题:

I want to catch exceptions thrown by classes implementing Processor interface. In aspect I need an access to processor, which throws the exception. I define following pointcut:

@Pointcut("target(some.package.Processor) && args(message)")
  public void processor(Message message) {
}

And aspect:

@AfterThrowing(pointcut="processor(message)", throwing="ex")
public void onExceptionInProcessor(Processor target, Exception ex, Message message) {
  // code skipped
}

However, I get following exception:

Caused by: java.lang.IllegalArgumentException: error at ::0 formal unbound in pointcut 
    at org.aspectj.weaver.tools.PointcutParser.parsePointcutExpression(PointcutParser.java:301) ~[aspectjweaver-1.6.12.jar:1.6.12]
    at org.springframework.aop.aspectj.AspectJExpressionPointcut.buildPointcutExpression(AspectJExpressionPointcut.java:207) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.aspectj.AspectJExpressionPointcut.buildPointcutExpression(AspectJExpressionPointcut.java:193) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.aspectj.AspectJExpressionPointcut.checkReadyToMatch(AspectJExpressionPointcut.java:182) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.aspectj.AspectJExpressionPointcut.getClassFilter(AspectJExpressionPointcut.java:163) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.support.AopUtils.canApply(AopUtils.java:209) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.support.AopUtils.canApply(AopUtils.java:263) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.support.AopUtils.findAdvisorsThatCanApply(AopUtils.java:295) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findAdvisorsThatCanApply(AbstractAdvisorAutoProxyCreator.java:117) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.findEligibleAdvisors(AbstractAdvisorAutoProxyCreator.java:87) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator.getAdvicesAndAdvisorsForBean(AbstractAdvisorAutoProxyCreator.java:68) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.wrapIfNecessary(AbstractAutoProxyCreator.java:359) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator.postProcessAfterInitialization(AbstractAutoProxyCreator.java:322) ~[spring-aop-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:407) ~[spring-beans-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1461) ~[spring-beans-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519) ~[spring-beans-3.1.0.RELEASE.jar:3.1.0.RELEASE]
    ... 58 common frames omitted

What is a correct way of binding target object to aspect? The only way I've found is binding JoinPoint, but it suggests following:

Unless you specifically need this reflective access, you should use the target pointcut designator to get at this object for better static typing and performance

Does anyone one how to do this?

回答1:

Your target should refer to one of the parameter names in the method. For example saying

@Pointcut("target(myProc) && args(message)")
public void processor(Processor myProc, Message message) {
}

will give you the Processor in type safe way in myProc variable.