Others are more expert than I but I believe the difference is that f1/f2
invokes are using hard Java Objects and f3/f4 invokes are using MethodHandles
with generic arguments.
> On May 16, 2017, at 3:36 PM, xu qingyi <bphan...@live.com> wrote:
>
> thx, Jim, I hava tried your solution and it works. but it needs to
> invoke java method so it's more complex. After all, what's the different
> between f1, f2 and f4.
>
> 2017年5月17日 上午2:28，"Jim Laskey (Oracle)" <james.las...@oracle.com>写道：
> It could have inferred that you meant to pass in a single element object
> array. Nashorn needs a bit more to determine that you wanted to convert to an
> java object array.
>
> System.out.println(nashorn.eval("var ObjectArray =
> Java.type('java.lang.Object[]'); f4(Java.to([1,2], ObjectArray))"));
>
> or more simply
>
> System.out.println(nashorn.eval("f4(Java.to([1,2]))"));
>
> Generally, Nashorn only automatically converts primitive types.
>
>
> — Jim
>
>
>
>
> > On May 16, 2017, at 3:03 PM, qiyi <bphan...@gmail.com> wrote:
> >
> > Hi, all, I'am trying to add a function to nashorn engine's bindings, and
> > these methods I have tried:
> >
> > public class MyFunction implements Function<Object[], Object> {
> >
> > @Override
> > public Object apply(Object[] objects) {
> > return Arrays.toString(objects);
> > }
> >
> > public Object f2(Object[] objects) {
> > return Arrays.toString(objects);
> > }
> >
> > public Object f3(Object object) {
> > return object;
> > }
> >
> > public Object f4(Object[] objects) {
> > return Arrays.toString(objects);
> > }
> >
> >
> > public static void main(String[] args) throws ScriptException {
> > MyFunction myFunction = new MyFunction();
> >
> > ScriptEngineManager manager = new ScriptEngineManager();
> > ScriptEngine nashorn = manager.getEngineByName("nashorn");
> > Bindings bindings = nashorn.getBindings(ScriptContext.ENGINE_SCOPE);
> >
> > bindings.put("f1", myFunction);
> > bindings.put("f", myFunction);
> > bindings.put("f3", (Function<Object, Object>) myFunction::f3);
> > bindings.put("f4", (Function<Object[], Object>) myFunction::f4);
> >
> > System.out.println(nashorn.eval("f1([1,2])")); // run ok, ret: [1,2]
> > System.out.println(nashorn.eval("f.f2([1,2])")); // run ok, ret: [1,
> > 2]
> > System.out.println(nashorn.eval("f3(\"f3\")")); // run ok, ret: f3
> > System.out.println(nashorn.eval("f4([1,2])")); // run fail,
> > ClassCastException: ScriptObjectMirror cannot be cast to
> > [Ljava.lang.Object
> > }
> > }
> >
> >
> > The problem is the f4 function, this method pointer receive Object[]
> > parameter and nashorn will throw exception with ClassCastException.
> >
> > But why nashorn could not infer the parameter type and auto convert
> > the js array to java array, will it be a bug of nashorn
>
>
