How to execute JavaScript file in Java8 using Nashorn

Question

I want to call the Javascript inside my Java class but not able to find correct way. I read somewhere it can be done using Nashorn. could someone please let me know the exact way.

Answer 1

You can call JavaScript using "ScriptEngineManager" as below.

ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
    ScriptEngine engine = scriptEngineManager.getEngineByName("nashorn");
    try {
        engine.eval(new FileReader("src\\demo.js"));
        Invocable invocable = (Invocable)engine;
        Object result = invocable.invokeFunction("fun1", "User");
        System.out.println(result);

    } catch (ScriptException e) {
        e.printStackTrace();
    }

And you JS file demo.js will looks something like below.

var fun1 = function(name){
print('Hi,'+name);
return "Greeting from javascript";
}