Method Transfer with Byte Buddy

Question

I have a problem getting a simple example of working with Byte Buddy, here is my code:

import static java.util.Arrays.asList;
import java.util.stream.Stream;
import net.bytebuddy.ByteBuddy;
import net.bytebuddy.dynamic.loading.ClassLoadingStrategy;
import net.bytebuddy.implementation.MethodDelegation;

public class Foo {
  public static class Bar {
    public void bar (String s, Integer i) {
      System.out.println ("s:" + s + " i:" + i);
    }
  }
  public static class Baz {
    public void baz (Integer i, String s) {
      System.out.println ("i:" + i + " s:" + s);
    }
  }

  public static void main (String[] args) {
    try {
      Class<?> c = new ByteBuddy ()
        .subclass (Object.class)
        .defineMethod ("bar", Void.class, asList (String.class, Integer.class), 1)
        .intercept (MethodDelegation.to (new Bar ()))
        .defineMethod ("baz", Void.class, asList (Integer.class, String.class), 1)
        .intercept (MethodDelegation.to (new Baz ()))
        .make ()
        .load (Foo.class.getClassLoader (), ClassLoadingStrategy.Default.WRAPPER)
        .getLoaded ();
      Stream.of (c.getDeclaredMethods ()).forEach (System.out::println);
    } catch (Exception e) {
      e.printStackTrace ();
    }
  }
}

Which I would expect to work and forward calls to reputable interceptor instances, however I get this exception:

java.lang.IllegalArgumentException: None of [protected void java.lang.Object.finalize() throws java.lang.Throwable, public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException, public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException, public final void java.lang.Object.wait() throws java.lang.InterruptedException, public boolean java.lang.Object.equals(java.lang.Object), public java.lang.String java.lang.Object.toString(), public native int java.lang.Object.hashCode(), public final native java.lang.Class java.lang.Object.getClass(), protected native java.lang.Object java.lang.Object.clone() throws java.lang.CloneNotSupportedException, public final native void java.lang.Object.notify(), public final native void java.lang.Object.notifyAll(), public void Foo$Bar.bar(java.lang.String,java.lang.Integer)] allows for delegation from public java.lang.Void net.bytebuddy.renamed.java.lang.Object$ByteBuddy$P87HQ3lQ.bar(java.lang.String,java.lang.Integer)
at net.bytebuddy.implementation.bind.MethodDelegationBinder$Processor.process(MethodDelegationBinder.java:881)
at net.bytebuddy.implementation.MethodDelegation$Appender.apply(MethodDelegation.java:1218)
at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyBody(TypeWriter.java:510)
at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod.apply(TypeWriter.java:444)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:3193)
at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:1481)
at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:234)
at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$AbstractDelegatingBuilder.make(DynamicType.java:2177)
at Foo.main(Foo.java:55)

The strangest part is at the very end of the exception message:

[...] public void Foo$Bar.bar(java.lang.String,java.lang.Integer)] allows for delegation from public java.lang.Void net.bytebuddy.renamed.java.lang.Object$ByteBuddy$P87HQ3lQ.bar(java.lang.String,java.lang.Integer)

What am I doing wrong?

Answer 1

You are correct in your assumption. Byte Buddy cannot assign a voidnon-type to a type void. However, Byte Buddy can assign to the nullreference type from the void method when you annotate the interceptors with @RuntimeType:

public class Bar {
  @RuntimeType
  public void bar (String s, Integer i) {
    System.out.println ("s:" + s + " i:" + i);
  }
}
public class Baz {
  @RuntimeType
  public void baz (Integer i, String s) {
    System.out.println ("i:" + i + " s:" + s);
  }
}

Answer 2

, , void void , ,