Mixing Nashorn with Rhino

[Benjamin Sieffert]

Hi Paul,

to nashorn, your rhino function is just a POJO of type
org.mozilla.javascript.InterpretedFunction. There's nothing about it
looking like a "function".
So either you use call(Context cx, Scriptable scope, Scriptable thisObj,
Object[] args) or similar on InterpretedFunction, or you wrap it in a class
implementin jdk.nashorn.api.scripting.JSObject and handroll the logic.
Might turn out to not be quite easy – I have no idea how similar rhino and
nashorn are, under the hood.

Someone else might be able to chime in with more insight.

Greetings

On 15 May 2015 at 11:42, Paul Bakker <pgbakker at gmail.com> wrote:

> Hi,
>
> Bare with me for a sec while I explain my setup: I'm working with a Java
> application which using Rhino to provide scripting capabilities.
>
> I now need to provide from within this Rhino scripting environment a new
> level of scripting access, which should have a limited scope, as in it
> shouldn't have access to all stuff the Rhino scripting layer already has
> access to.
>
> While I could probably achieve this from the Rhino scripting layer by
> instantiating a new Rhino scripting engine/scope/context/...., I came up
> with the idea to use Nashorn instead. This way I achieve a few things:
> 1: the Nashorn scripting environment is completely encapsulated from
> whatever is already accessible from the Rhino scripting environment
> 2: better performance of the JavaScript executed in the new Nashorn-based
> scripting layer
> 3: up to date JavaScript support (now, but mostly in the future (ES2015
> and beyond))
> 4: Gain experience myself in using Nashorn
>
> Now, I've gotten so far as to instantiate a Nashorn script engine with
> only plain JavaScript API exposed from Rhino:
>     var scl = java.lang.ClassLoader.getSystemClassLoader()
>     var factory =
> java.lang.Class.forName('jdk.nashorn.api.scripting.NashornScriptEngineFactory',
> true, scl).getConstructor().newInstance()
>     var nashornEngine =  factory.getScriptEngine(['-strict', '--no-java',
> '--no-syntax-extensions'])
>
> Next I try to expose some object with methods in Nashorn and this is where
> I am running into an issue: While I can expose the object in Nashorn
> without problems, when a script in Nashorn tries to execute one of the
> methods of the object, it fails with the following error:
> => testNashorn()
> org.mozilla.javascript.WrappedException: Wrapped
> javax.script.ScriptException: TypeError:
> org.mozilla.javascript.InterpretedFunction at 6ada780a is not a function in
> <eval> at line number 1 (C:\workspaces\test\master\engine\engine.js#9)
>
> The code of my attempt is below. Note that this code is executed from
> within Rhino:
> function testNashorn() {
>     var logger = {
>         debug: function(){
>             java.lang.System.out.println('testing')
>         }
>     }
>
>     nashornEngine.getContext().setAttribute('log1', logger,
> Packages.javax.script.ScriptContext.ENGINE_SCOPE)
>     nashornEngine.eval("log1.debug('hello')")
>
>     nashornEngine.put('log2', logger)
>     nashornEngine.eval("log2.debug('hello')")
> }
>
> My understanding is that Nashorn isn't able to execute a function that is
> defined in Rhino (in this case the debug method of the logger object).
>
> Now my basic question is: can this be done, some way or the other? I know
> this is not your typical setup, but it is the one I have to work with and I
> really like to implement the required functionality using Nashorn for the
> stated reasons.
>
> Hope someone can shed some light on this.
>
> TIA,
>
> Paul
>



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Benjamin Sieffert
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