Implements/Implementing

Sometimes when using $instanceof{}, you might just be interested in the methods coming from the implemented interface. There are two keywords that can be used in place of a method expression to acheive this:

$implements{} - matches the methods from the interface(s) listed, but ignores any super interfaces
$implementing{} - matches the methods from the interface(s) listed AND their super interfaces

In this example ImplementsInterface extends ImplementsSuperInterface, and ImplementingInterface extends ImplementingSuperInterface.

<aop>
   <interceptor class="implementz.TestInterceptor"/>
   <bind pointcut="execution(void $instanceof{implementz.ImplementsInterface}->$implements{implementz.ImplementsInterface}(..))">
      <interceptor-ref name="implementz.TestInterceptor"/>
   </bind>
   <bind pointcut="execution(void $instanceof{implementz.ImplementingInterface}->$implementing{implementz.ImplementingInterface}(..))">
      <interceptor-ref name="implementz.TestInterceptor"/>
   </bind>
</aop>

So for these bindings we will intercept our POJO class on all the methods coming from ImplementsInterface, i.e. methodsFromImplements(), and all methods coming from ImplementingInterface and ImplementingInterface's super interfaces, i.e. methodFromImplementingSuper() and methodFromImplementsSuper().

Note that if your class implements several interfaces, you can specify more than one interface in the $implements{}, $implementing{} list, as shown in this example pointcut expression:

   execution(void $instanceof{X}->$implementing{X,Y,Z}(..))

Running

To compile and run:

  $ ant

It will javac the files and then run the AOPC precompiler to manipulate the bytecode, then finally run the example. The output should read as follows:

run:
     [java] --- POJO ---
     [java] --- POJO.methodFromImplements ---
     [java] <<< TestInterceptor intercepting
     [java] *** POJO methodFromImplements
     [java] >>> Leaving Trace
     [java] --- POJO.methodFromImplementingSuper (should not intercept) ---
     [java] *** POJO methodFromImplementsSuper
     [java] --- POJO.methodFromImplementing ---
     [java] <<< TestInterceptor intercepting
     [java] *** POJO methodFromImplementing
     [java] >>> Leaving Trace
     [java] --- POJO.methodFromImplementingSuper ---
     [java] <<< TestInterceptor intercepting
     [java] *** POJO methodFromImplementingSuper
     [java] >>> Leaving Trace
     [java] --- POJO.ownMethod (should not intercept) ---
     [java] *** POJO ownMethod