How to pass Javascript Object from Java to Javascript using Nashorn

Question

I have a JavaScript object in String form (actually coming from database) which I need to pass to a Javascript function using Nashorn (Java 8). The Engine treats the parameter passed as a string in javascript. I want it to identify it as a Javascript object.

Below is the code snippet:

String script = "function genData(dataModel) { return 'hello world '+ dataModel.url.value + ' done'; }";  

//"{url : {value : "abc.com",type  : "string"},layout : {value : "",type  : "string"}}";  

String dataModel = "{url : {value : \"abc.com\",type  : \"string\"},layout : {value : \"\",type  : \"string\"}}";

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("JavaScript");
Invocable inv = (Invocable) engine;
result = inv.invokeFunction("genData", dataModel);

The error I get is:
javax.script.ScriptException: TypeError: Cannot read property "value" from undefined in at line number 1

Well the idea was to show how the javascript object looks like and make it less cryptic. I have moved it as a comment and escaped the string if that helps — iqz
– iqz, Commented May 16, 2017 at 23:16

A. Sundararajan · Accepted Answer · 2017-05-13 02:05:22Z

5

You could convert dataModel string as JSON first - either in the function itself or elsewhere and then pass it.

Example:

String dataModel = ...;
// convert the string as a JSON object
engine.put("dataModel", dataModel);
JSObject obj = (JSObject)engine.eval("JSON.parse(dataModel)");
...
// dataModel is a script object - as it is a result of JSON.parse
// pass it as parameter for genData
inv.invokeFunction("genData", obj);

answered May 13, 2017 at 2:05

A. Sundararajan

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Comments

Andrejs · Accepted Answer · 2018-02-27 14:36:19Z

2

If your dataModel is a simple Java Map then you can pass it to invokeFunction directly as a parameter. For more advanced uses your parameter should implement the Bindings interface.

To make this easier I wrote a library called json:

Example:

    Json j = new Json("a", 5);
    Double result = (Double) eng.eval("a+1", j);

answered Feb 27, 2018 at 14:36

Andrejs

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