6 Replies Latest reply on Jul 5, 2006 8:18 AM by kabirkhan

    Aop field interceptor to provide filtering for method call s

    ben.wang Jun 29, 2006 11:01 PM

      Kabir,

      This is the issue that we discussed in Vegas:
      http://jira.jboss.com/jira/browse/JBCACHE-110

      Basically what I am looking for from PojoCache point of view is that, say, if while I am doing all field interception, but if it is from certain method call stack, then I don't care about it. So either aop not to intercept it or I have some knowledge that I can skip it.

      Is it possible for AOP to provide such funcationality?

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        • 1. Re: Aop field interceptor to provide filtering for method ca
          kabirkhan
          kabirkhan Jun 30, 2006 7:58 AM (in response to ben.wang)

          I think the simplest approach is to have an interceptor at the start of the chain, which manages this.

          public class ReentrancyStopperInterceptor implements Interceptor
{
 ThreadLocal done = new ThreadLocal();

 private Object invoke(Invocation invocation) throws Throwable
 {
 boolean wasDone = ((Boolean)done.get()).booleanValue();

 try
 {
 if (!wasDone)
 {
 done.set(Boolean.TRUE);
 return invocation.invokeNext();
 }
 else
 {
 //Needs adding, and will invoke target joinpoint skipping the rest of the chain
 return invocation.dispatch();
 }
 }
 finally
 {
 if (!wasDone)
 {
 done.set(Boolean.FALSE);
 }
 }

 return ret;
 }
}


          I could implement the new dispatch() method pretty quickly, and I think this interceptor should belong in the aop module.

          Similar functionality _could_ be added to the woven bytecode, but I don't think it is a good idea to code use-case stuff in there.


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          • 2. Re: Aop field interceptor to provide filtering for method ca
            ben.wang Jun 30, 2006 8:35 AM (in response to ben.wang)

            Sounds good. But we need to consider the following calling stack:

            pojo.methodA();
pojo.methodB();
...
pojo.methodB(); // so we can skip this field interception
pojo.methodA(); // oops, it will fail.


            So in essence, we need to have a local thread array done[] such that this will work properly.

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            • 3. Re: Aop field interceptor to provide filtering for method ca
              kabirkhan
              kabirkhan Jun 30, 2006 8:51 AM (in response to ben.wang)

              Hmmm, I'm not getting you, please elaborate.

              BTW the interceptor I outlined was for field interception, and would be used only for a field for a particular instance. I see now that it was a bit too simple. It should really be scoped PER_JOINPOINT, so that the "done" book-keeping is only done for a particular field. Now, this is not possible with the existing InstanceAdvisor API, since per instance aspect added there apply to ALL joinpoints. However, with the new AOP 2 weaving this is possible. Take a look at
              org.jboss.test.aop.dynamicgenadvisor.DynamicTester to see how this works.

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              • 4. Re: Aop field interceptor to provide filtering for method ca
                ben.wang Jul 5, 2006 2:54 AM (in response to ben.wang)

                Ok, what I meant more properly is the PER_JOINTPOINT scope that you proposed where we track the recursion call at the joint point scope.

                Now which test specifically you were referring to? I don't see any PER_JOINTPOINT scope test. :-)

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                • 5. Re: Aop field interceptor to provide filtering for method ca
                  kabirkhan
                  kabirkhan Jul 5, 2006 4:36 AM (in response to ben.wang)

                  I meant the DynamicTester. It shows how the new per instance API works :-)

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                  • 6. Re: Aop field interceptor to provide filtering for method ca
                    kabirkhan
                    kabirkhan Jul 5, 2006 8:18 AM (in response to ben.wang)

                    Hi Ben,

                    I have added this method to the invocation object in head. I have called it invokeTarget() instead of dispatch().

                    http://jira.jboss.com/jira/browse/JBAOP-270

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