BuddyTesting.java

package com.webobjects.foundation;

import java.lang.reflect.Method;
import java.util.Optional;

import net.bytebuddy.ByteBuddy;
import net.bytebuddy.agent.ByteBuddyAgent;
import net.bytebuddy.asm.Advice;
import net.bytebuddy.dynamic.loading.ClassReloadingStrategy;
import net.bytebuddy.matcher.ElementMatchers;

public class BuddyTesting {

    public static void main( String[] args ) {
        ByteBuddyAgent.install();

        new ByteBuddy()
                .redefine( NSKeyValueCoding.DefaultImplementation.class )
                .visit( Advice.to( KVCAdvisor.class )
                        .on( ElementMatchers.named( "valueForKey" ) ) )
                .make()
                .load(
                        NSKeyValueCoding.DefaultImplementation.class.getClassLoader(),
                        ClassReloadingStrategy.fromInstalledAgent() );
    }

    public static class KVCAdvisor {
        @Advice.OnMethodExit
        static void exit( @Advice.Return( readOnly = false ) Object returnValue, @Advice.Origin Method originalMethod, @Advice.Argument( 0 ) Object param0, @Advice.Argument( 1 ) String param1 ) throws Exception {
            Object originalValue = originalMethod.invoke( param0, new Object[] { param0, param1 } );
            returnValue = doMyOwnStuffTo( originalValue );
        }
    }

    private static Object doMyOwnStuffTo( Object originalValue ) {
        // TODO: Do stuff to original value
        return originalValue;
    }
}