Using Nashorn/JavaScript to Create a Java GUI application

Question

I am attempting to create an application(game) that would use java to operate the physics,logic, etc. but would use existing javascript libraries for doing things like scripting, graphics, and the ui, but when loading a chart.js(and other libraries) through nashorn nashorn.eval("load('chart.js')"); I get the following (or similar for other libraries) Exception in thread "main" javax.script.ScriptException: ReferenceError: "window" is not defined in chart.js at line number 668.

Is it possible to use these libraries as-is, or would any modification by necessary, and how could I display scripts in a java application(or is it even possible, with or without nashorn)?

Thanks.

JavaScript libraries intended to be used as part of web applications expect to run in a browser environment, with all the common browser services (especially, of course, the rendering engine, the DOM, and so on). None of that exists in a Java application. — Pointy
– Pointy, Commented Jul 20, 2015 at 1:16

A. Sundararajan · Accepted Answer · 2015-07-24 04:58:12Z

As mentioned you can use JavaFX WebView to load "browser" HTML+script into Nashorn JavaFX GUI. You can load generated HTML as well as from a URL.

Simple examples:

http://hg.openjdk.java.net/jdk9/dev/nashorn/file/f884dff432a7/samples/showsysprops.js http://hg.openjdk.java.net/jdk9/dev/nashorn/file/f884dff432a7/samples/showenv.js

You can also access "browser" JS/DOM objects from Nashorn engine and manipulate with nashorn script (if needed):

http://hg.openjdk.java.net/jdk9/dev/nashorn/file/f884dff432a7/samples/browser_dom.js

Given that you're going to use Java libraries, you may also want to consider JavaFX GUI without WebView as well (or even mix-n-match as needed). Few simple examples here:

http://hg.openjdk.java.net/jdk9/dev/nashorn/file/f884dff432a7/samples/jsonviewer.js http://hg.openjdk.java.net/jdk9/dev/nashorn/file/f884dff432a7/samples/time_color.fx http://hg.openjdk.java.net/jdk9/dev/nashorn/file/f884dff432a7/samples/fxml_example.js

Somewhat complex example of loading a third-party HTML+script into a JavaFX GUI and extending it from nashorn script:

https://gist.github.com/sundararajana/7b19ec08a8878426af5e

David P. Caldwell · Accepted Answer · 2015-07-22 23:48:29Z

1

You may, however, be able to persuade this to run in the JavaFX WebView container. I have not tried using advanced JavaScript libraries in the container but my experience is:

The container works fairly well,
It is difficult to debug applications running in it, as there are very few mechanisms for doing so,
The mechanisms for communicating back to the Java application are fairly good,
You can provide custom handling for application-specific protocols for URLs, but it is not clear to me how these would affect the WebView's security model (unless you updated the http: or https: stream handlers, which appears to be possible using the URL.setURLStreamHandlerFactory method).

edited Jul 22, 2015 at 23:48

answered Jul 22, 2015 at 10:49

David P. Caldwell

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2 Comments

jewelsea Over a year ago

Webview works based on the in-built Java url handling mechanism, which is customizable, though I guess the original poster probably won't need custom protocol handling.

David P. Caldwell Over a year ago

I haven't tried it, but I am going to rely on your assertion and change my answer, as it does make sense to me (I also discovered, for example, that WebView installs a default cookie handler for the URL stuff, so it seems completely sensible that it's using the generic URL stuff).

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