Using a script to implement a Java interface with variadic methods

[A. Sundararajan]

Hi,

Sorry for the delayed response. Yes, this seems to be a bug. I've filed

JDK-8011065 - Problems when script implements an interface with variadic 
methods

to track this issue. Thanks for reporting this issue.

-Sundar

On Wednesday 27 March 2013 08:24 PM, John Keeping wrote:
> I get surprising results using Nashorn to implement a Java interface via
> a script when that interface contains variadic methods.
>
> The easiest way to explain is probably with an example:
>
> If I have a Java interface:
>
>      public interface MyInterface {
>          void test(int i, String... strings);
>      }
>
> and I implement this in a script:
>
>      function test(i, strings) {
>          print('i = ' + i);
>          print('strings = ' + strings);
>      }
>
> which I then wrap from Java:
>
>      ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
>      engine.eval(script);
>      Invocable inv = (Invocable) engine;
>      MyInterface obj = inv.getInterface(MyInterface.class);
>
> Calling the "test" method:
>
>      obj.test(10, "one", "two", "three");
>
> gives:
>
>      i = 10
>      strings = one
>
> when I would expect something like:
>
>      i = 10
>      strings = [Ljava.lang.String;@deadbeef
>
> (not useful output, but it illustrates the point I hope).
>
>
> At this point, I considered changing the script to use "arguments" to
> access the passed in values:
>
>      function test(i, strings) {
>          for (var index = 0; index < arguments.length; index++)
>              print('arg ' + index + ' = ' + arguments[index]);
>      }
>
> but that gives an error trying to get the interface:
>
>      java.lang.invoke.WrongMethodTypeException: Parameter counts differ:
>          (Object[])Object vs. (int,String[])void
>
>
> Is this a deficiency in Nashorn's handling of variadic methods or am I
> missing something here?
>
>