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From: "James Carman" <james@carmanconsulting.com>
To: "'Jakarta Commons Developers List'" <commons-dev@jakarta.apache.org>
Subject: RE: [HiveMind] New interceptor support
Date: Tue, 25 Nov 2003 08:44:28 -0500
Organization: Carman Consulting, Inc.
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In-Reply-To: <opry61c3g8wo6mmv@mail.yahoo.de>
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I like the idea of this hybrid approach!  I am NOT a fan of using =
javassist
to write interceptors.  I am writing an article for TheServerSide.com =
about
HiveMind currently.  Is this code available somewhere?  I don't plan on
demonstrating how to write a purely javassist-based interceptor, as I do =
not
feel it is very intuitive.  However, this simpler approach does seem to =
be a
nice compromise and I would like to present it.

-----Original Message-----
From: Christian Essl [mailto:christianessl@yahoo.de]=20
Sent: Tuesday, November 25, 2003 7:38 AM
To: commons-dev@jakarta.apache.org
Subject: [HiveMind] New interceptor support


Javassist is fast and impressingly easy for byte-code generation, =
however=20
it is by no way that comfortable (to code, test and debugg) as plain =
java.=20
Therefore I've implemented an abstract ServiceInterceptorFactory which=20
allows the user to attach MethodInterceptors to the methods of an=20
interface. (A common pattern used by aopalliance, spring, cglib etc). Ie =
a=20
simple tracing interceptor looks like this:

public class TracingMethodInterceptor implements MethodInterceptor

 public Object invoke(Invocation invocation, Object target, Object[] =
args)=20
throws Throwable
 {
    System.out.println("method: "+invocation.getMethod()+" is called =
with=20
args: "+args);
    Object ret =3D invocation.proceed(target, args); //this invokes the =
next=20
method in the interceptor chain
    System.out.println("method: "+invocation.getMethod()+" returned:=20
"+args);
    return ret;
 }
}

Both the interceptor and the Invocation are created using Javassist,=20
therefore it is in terms of speed (according to my rudimentary testings) =

between a plain Javaassist interceptor and a dyna-proxy interceptor.

Comparing the existing Hivemind Logging with the same code using the=20
MethodInterceptor and with a DynaProxy for 5.000.000 repetitions the =
times=20
(ms) are as follows: (The numbers are not stable but the direction is =
quite=20
clear)

method: Object getObject()
executing MethodLog took: 1000
executing HivemindLog took: 359
executing DynaProxyLog took: 1360

method: void setObject(Object);
executing MethodLog took: 968
executing HivemindLog took: 516
executing DynaProxyLog took: 1766

method (9 prim params): int =
add(int,int,byte,short,char,double,long,float);
executing MethodLog took: 3063 (more primitives and arguments means =
bigger=20
args[] and boxing/unboxing)
executing HivemindLog took: 594
executing DynaProxyLog took: 4031

As I see interceptors for general use should be created using =
javaassist,=20
however other interceptors (which just add some custom AOP for some=20
components) could well be implemented using MethodInterceptors. Here the =

higher convinience pays off.

--=20
Christian Essl http://jucas.sourceforge.net

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