Using Backbone Models from Nashorn JS Engine

Nashorn6.java

package com.winterbe.java8;

import jdk.nashorn.api.scripting.ScriptObjectMirror;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

/**
 * Using Backbone Models from Nashorn.
 *
 * @author Benjamin Winterberg
 */
public class Nashorn6 {

    public static void main(String[] args) throws Exception {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
        engine.eval("load('res/nashorn6.js')");

        Invocable invocable = (Invocable) engine;

        Product product = new Product();
        product.setName("Rubber");
        product.setPrice(1.99);
        product.setStock(1337);

        ScriptObjectMirror result = (ScriptObjectMirror)
                invocable.invokeFunction("calculate", product);
        System.out.println(result.get("name") + ": " + result.get("valueOfGoods"));
    }

    public static void getProduct(ScriptObjectMirror result) {
        System.out.println(result.get("name") + ": " + result.get("valueOfGoods"));
    }

}

nashorn6.js

load('http://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.6.0/underscore-min.js');
load('http://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js');


// simple backbone model:
// valueOfGoods will automatically be calculated when stock or price changes
var Product = Backbone.Model.extend({
    defaults: {
        stock: 0,
        price: 0.0,
        name:'',
        valueOfGoods: 0.0
    },

    initialize: function() {
        this.on('change:stock change:price', function() {
            var stock = this.get('stock');
            var price = this.get('price');
            var valueOfGoods = this.getValueOfGoods(stock, price);
            this.set('valueOfGoods', valueOfGoods);
        });
    },

    getValueOfGoods: function(stock, price) {
        return stock * price;
    }
});

var product = new Product();
product.set('name', 'Pencil');
product.set('stock', 1000);
product.set('price', 3.99);


// pass backbone model to java method
var Nashorn6 = Java.type('com.winterbe.java8.Nashorn6');
Nashorn6.getProduct(product.attributes);


// bind java object to backbone model and pass result back to java
var calculate = function(javaProduct) {
    var model = new Product();
    model.set('name', javaProduct.name);
    model.set('price', javaProduct.price);
    model.set('stock', javaProduct.stock);
    return model.attributes;
};