ability to inject custom properties into a JS object

[Radu Cotescu]

Hi Sundar,

Thank you for your quick reply! I did read about JSAdapter and JSObject
before my initial email but I don't think they actually do what I want.

In my use-case I need to be able to interfere with object translation (from
Java to JavaScript) for all instances of a certain Java class, not just for
specific objects. Is there any way I could achieve this (something similar
to Rhino's host objects [2])?

Thanks,
Radu

[2] -
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/Rhino/Embedding_tutorial#JavaScript_host_objects

On Mon, 15 Jun 2015 at 15:23 A. Sundararajan <
sundararajan.athijegannathan at oracle.com> wrote:

> Please note that nashorn has support to handle Java objects with 'bean
> style' property support. And you could implement Java interfaces and
> extend Java abstract classes in script.  java.util.Map objects are
> treated specially to provide key-value access as properties.
> java.util.ArrayList objects are treated like arrays (indexed element
> access, length property for size). These could be used provide
> script-friendly access to your existing Java classes.
>
> But, if you want to write script "proxies" to trap property access etc.,
> then there are two ways:
>
> 1) JSAdapter - you'd write JSAdapter wrapper in script.
>
> Example:
>
>
> https://wiki.openjdk.java.net/display/Nashorn/Nashorn+extensions#Nashornextensions-JSAdapterconstructor
>
> 2) Implementing jdk.nashorn.api.scripting.JSObject.
>
>
> https://docs.oracle.com/javase/8/docs/jdk/api/nashorn/jdk/nashorn/api/scripting/JSObject.html
>
> AbstractJSObject (
>
> https://docs.oracle.com/javase/8/docs/jdk/api/nashorn/jdk/nashorn/api/scripting/AbstractJSObject.html
> ) provides empty/null implementation for most methods and so you can
> extend it as well.
>
> In addition, any @FunctionalInterface object
> (java.util.functions.Function etc) can be called as a script function.
> So, your script functions could just be Java functional interface objects.
>
> Example:
>
>
> https://wiki.openjdk.java.net/display/Nashorn/Nashorn+extensions#Nashornextensions-Plugging-inyourownJSObject
>
> Hope this helps,
> -Sundar
>
> On Monday 15 June 2015 05:42 PM, Radu Cotescu wrote:
> > Hello,
> >
> > I've recently started looking into replacing Rhino with Nashorn as the
> > JavaScript scripting engine for Apache Sling (see SLING-4801 [0]).
> >
> > Once nice Rhino feature that I don't seem to be able to easily map to
> > something from Nashorn is the ability to provide my own object wrappers,
> > such that the resulting JS object contains some custom properties. I did
> > notice this thread [1] but I wasn't able to reach to a conclusion
> regarding
> > this feature.
> >
> > Is there a way to easily implement this custom object translation layer
> > without having to implement a JSObject? The problem with this approach is
> > that Sling script developers will have to use these custom wrapper
> classes
> > (JSObjects) instead of the APIs directly available through the Bindings,
> > making scripts written for the Rhino implementation incompatible.
> >
> > Thanks,
> > Radu
> >
> > [0] - https://issues.apache.org/jira/browse/SLING-4801
> > [1] -
> >
> https://www.mail-archive.com/nashorn-dev%40openjdk.java.net/msg01485.html
>
>