[jboss-user] [JBoss AOP] - Is there a static vs. dynamic binding problem with jboss aop

[manu4ever]

Further to my question below, here's another example where something really seriously screwy is happening. The basic infrastructure comes from the docs/aspect-framework/examples/annotation example, but some of the files are modified and there is one new file:

Driver.java
=======

public class Driver {
   public static void main(String[] args) {
      SUBPOJO spojo = new SUBPOJO(2);
      spojo.someMethod();
   }
}

POJO.java
=======

public class POJO {
   @trace int field;

   public POJO() {
   }

   public POJO(int i) {
        field = i;
   }

  @billable public void someMethod() {
      System.out.println("someMethod");
        System.out.println("FIELD = " + field);
   }
}


SUBPOJO.java
=========

public class SUBPOJO extends POJO {
   private int field;
   public SUBPOJO() {
   }

   public SUBPOJO(int i) {
        super(i/2);
        field = i;
   }

   public void someMethod() {
        System.out.println("ENTERING SUBPOJO:someMethod");
        super.someMethod();
      System.out.println("LEAVING SUBPOJO:someMethod");
   }
}

Here is the jboss-aop.xml file:

<?xml version="1.0" encoding="UTF-8"?>
  | <aop>
  |    <bind pointcut="execution(POJO->@billable(..))">
  |        <interceptor class="BillingInterceptor"/>
  |    </bind>
  |    <bind pointcut="execution(* POJO->@billable(..))">
  |        <interceptor class="BillingInterceptor"/>
  |    </bind>
  |    <bind pointcut="all(@trace)">
  |        <interceptor class="TraceInterceptor"/>
  |    </bind>
  | </aop>

If I remove the "@trace" from the definition of field "field" in POJO.java then this works almost as expected:

run:
     [java] ENTERING SUBPOJO:someMethod
     [java] billing...[advisedMethod=public void POJO.someMethod(), unadvisedMethod=public void POJO.POJO$someMethod$aop(), metadata=null, targetObject=SUBPOJO at a4e743, arguments=null]
     [java] someMethod
     [java] FIELD = 1
     [java] LEAVING SUBPOJO:someMethod

FIELD is correctly displayed as 1 (the value of POJO.field). I say "almost" because I don't expect "billable" to be applied but suspect there's some means of making that happen.

However if I put back the "@trace" in the definition of "field" in POJO.java then this is what happens:

run:
     [java] <<< Trace : write field name: int POJO.field
     [java] >>> Leaving Trace
     [java] <<< Trace : write field name: int POJO.field
     [java] >>> Leaving Trace
     [java] ENTERING SUBPOJO:someMethod
     [java] billing...[advisedMethod=public void POJO.someMethod(), unadvisedMethod=public void POJO.POJO$someMethod$aop(), metadata=null, targetObject=SUBPOJO at 1112783, arguments=null]
     [java] someMethod
     [java] <<< Trace : read field name: int POJO.field
     [java] >>> Leaving Trace
     [java] FIELD = 2
     [java] LEAVING SUBPOJO:someMethod


Now the value read for field is WRONG. It is reading SUBPOJO.field rather than POJO.field. This appears to be because of the way that jboss aop rewrites the accessor method, switching from static to dynamic binding.

Even more oddly, if I change jboss-aop.xml to look like this:

<?xml version="1.0" encoding="UTF-8"?>
  | <aop>
  |    <bind pointcut="call(POJO->@billable(..))">
  |        <interceptor class="BillingInterceptor"/>
  |    </bind>
  |    <bind pointcut="call(* POJO->@billable(..))">
  |        <interceptor class="BillingInterceptor"/>
  |    </bind>
  |    <bind pointcut="all(@trace)">
  |        <interceptor class="TraceInterceptor"/>
  |    </bind>
  | </aop>


Then this is what happens:


run:
     [java] <<< Trace : write field name: int POJO.field
     [java] >>> Leaving Trace
     [java] <<< Trace : write field name: int POJO.field
     [java] >>> Leaving Trace
     [java] ENTERING SUBPOJO:someMethod
     [java] billing...SUBPOJO_1_MByMInvocation at 1989f84
     [java] ENTERING SUBPOJO:someMethod
     [java] billing...SUBPOJO_1_MByMInvocation at 110c424
     [java] ENTERING SUBPOJO:someMethod
     [java] billing...SUBPOJO_1_MByMInvocation at 1bd2664
     [java] ENTERING SUBPOJO:someMethod
     [java] billing...SUBPOJO_1_MByMInvocation at 1238bd2
     [java] ENTERING SUBPOJO:someMethod
     [java] billing...SUBPOJO_1_MByMInvocation at b0bad7
etc etc....

Ad infinitum, or at least until there is a stack overflow. This also appears to be down to a code rewrite that replaces static binding with dynamic binding.

Is there some configuration mechanism to avoid these errors - which are about as fundamental as I can imagine - or do I switch to aspectj which seems to get this right?



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