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springaopaspectj

How to hijacked/intercept method of a class which from third party(EclipseLink) jar or even JDK?

I try to hijack/intercept a method of a class in EclipseLink. I had tried Spring AOP and AspectJ and I failed. I want to do something when class org.eclipse.persistence.internal.localization.i18n.TraceLocalizationResource throw exception while calling method getString(..); My implementation as below:

@AfterThrowing(pointcut = "execution(* org.eclipse.persistence.internal.localization.i18n.TraceLocalizationResource.getString(..))",throwing="error")
    public void logAfterThrowing(JoinPoint joinPoint,Throwable error) {
....
}

And calssTraceLocalizationResource was called (I debug into it). But the hijack method wasn't called.

MY questions:

  1. Was I doing it in the wrong way ?
  2. The target class we want to hijack or intercept must be self-define type?
  3. What if I want to hijack a class in JDK like java.lang.String ?
Solution

    1. Basically the syntax looks okay, but I have not tried to replicate a full aspect from your code snippet here. Furthermore, I only use native AspectJ syntax and am not quite familiar with annotation-based syntax, so if there is a problem there I might not have seen it.

    2. No, but if you want to weave a library (JAR or unpacked into the file system) used by your main application, you must make sure that it is in the in-path for the weaver. Please consult AspectJ documentation for the syntax. Edit: I posted some helpful links in another answer earlier today.

    3. By default, packages org.aspectj, java and javax are excluded from weaving. For the latter two, there are command line switches to enable weaving. But LTW will be tricky at best and a pain in the a** (next to impossible) at worst because you have a hen-and-egg problem there: The AspectJ weaver runtime classes need the JDK, and JDK bootstrapping happens before any Java agent like the weaver is attached. So your best bet is compile-time weaving for JDK classes and then using the woven rt.jar later in your application. Even with compile-time weaving you might run into issues if your advice use JDK woven classes themselves. You want to make sure to avoid infinite recursions there. But it is possible.

      Update: Another hint which sometimes seems too simple to mention for someone who has used AspectJ for a while: Instead of an execution pointcut which makes it necessary to weave the target class, you may just use a call pointcut which intercepts (as the name implies) calls to the target everywhere in your client classes. It might be a little less efficient, but maybe your best and easiest bet unless you really want to take the trouble of weaving the JDK.