Pass parameter to JavaScript through Java code

Question

I'm trying to define a generic Formula, e.g. "a+b" and use it to pass parameters. Any ideas how to make this thing work?

    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("JavaScript");
    String Formula="a+b";

    engine.put("Formula", Formula);
    engine.put("a", "3");
    engine.put("b", "4");
    res = engine.eval("r = Formula").toString();
    System.out.println(res);

The output of the above code is "a+b" and not 7 as expected.

Look at this post: stackoverflow.com/questions/15682881/…

Distjubo
– Distjubo

2015-04-25 19:03:33 +00:00
Commented Apr 25, 2015 at 19:03 — Distjubo
– Distjubo, Commented Apr 25, 2015 at 19:03

xeeevi · Accepted Answer · 2015-04-25 19:36:52Z

2

To bind variable names with values, use Bindings.

I thing the following code solves your question:

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("JavaScript");
String formula="a+b";

Bindings bindings = engine.createBindings();
bindings.put("a", 3);
bindings.put("b", 4);

engine.setBindings(bindings, ScriptContext.ENGINE_SCOPE);

Object res = engine.eval(formula);
System.out.println(res.toString());

answered Apr 25, 2015 at 19:36

xeeevi

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