Re: Receiver class does not define or inherit an implementation of the resolved method

[Phil Eaton <phil@eatonphil.com>]

Aha! It gave my second apply method a different suffix. By reordering these
two methods the whole thing somehow works.

$ javap main\$0.class
Compiled from "main.scm"
public class main$0 implements io.jooby.Route$Handler {
  main$frame this$0;
  public java.lang.CharSequence apply(io.jooby.Context);
  public java.lang.Object apply$1(io.jooby.Context);
  public main$0(main$frame);
}


It's weird but I'll take it.



On Mon, Aug 30, 2021 at 12:40 PM Per Bothner <per@bothner.com> wrote:

> On 8/29/21 12:03 PM, Phil Eaton wrote:> Still new to Kawa. I'm trying to
> implement an interface (
> > io.jooby.Route$Handler
> > <
> https://github.com/jooby-project/jooby/blob/2.x/jooby/src/main/java/io/jooby/Route.java#L247
> >).
> > It only has a single non-default method, apply.
> >
> > Here's what I've got
> >
> > (define (route app method path handler)
> >    (let ((handler (object (io.jooby.Route$Handler)
> >                           #| This method exists just to stop Jooby from
> > trying to introspect Java code that doesn't exist because this isn't
> > written in Java. |#
> >                           ((apply (ctx ::io.jooby.Context)) ::string
> >                            #!null)
> >                           ((apply (ctx ::io.jooby.Context))
> > ::java.lang.Object
> >                            (handler ctx)))))
> >      (app:route method path handler)))
> >
> >
> > But when this gets exercised, I get:
> >
> > [worker-1-3] ERROR io.jooby.Jooby - GET /hello-world 500 Server Error
> > java.lang.AbstractMethodError: Receiver class main$0 does not define or
> > inherit an implementation of the resolved method 'abstract
> java.lang.Object
> > apply(io.jooby.Context)' of interface io.jooby.Route$Handler.
>
> I don't see anything obviously wrong.  One thing to try is instead of an
> anonymous class (with object) use a named class (with define-simple-class).
> The anonymous class is more convenient of course there is some extra
> "magic"
> (such as invisible fields) that might complicate things.
>
> > Also on a tangent, I was excited about the lambda shorthand for single
> > method objects. Like I said this interface only has a single non-default
> > method: apply. But I tried just calling `(app:route method handler)`
> > without wrapping it in the io.jooby.Route$Handler object but it still
> > failed. I guess it couldn't figure out this one method.
>
> Kawa has to be able to figure out at compile time that a specific
> class/interface
> is required before it can convert the lambda to an object.  (As far as I
> can
> remember, doing this conversion at run-time isn't implemented, and would be
> fairly complicated.)  So you may need to add some more type-specifiers.
>
> I suggest using javap to look at the generated classes, to see what is
> going on.
> --
>         --Per Bothner
> per@bothner.com   http://per.bothner.com/
>