Using Java Nashorn engine to validate javascript only

Question

Good morning.

I need to run javascript syntax validation through java but I'm struggling to find the best solution.

I did some tests with Nashorn using the following approach:

try
{
    ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
    Object retVal = engine.eval("findFieldValue(field);");
}
catch (ScriptException e)
{
    response.put("status", "parseexception");
    response.put("msg", e.getMessage());
}

Nashorn throws an exception saying both findFieldValue and field are undefined, which is correct. I don't need this kind of validation. All I need is to validate the syntax, like it's done by Esprima JS API

http://esprima.org/demo/validate.html

My question is. Can I ignore semantic validation with Nashorn, validating syntax only?

Thank you!

wrap it in an function?

Johannes Kuhn
– Johannes Kuhn

2018-08-03 17:35:47 +00:00
Commented Aug 3, 2018 at 17:35 — Johannes Kuhn
– Johannes Kuhn, Commented Aug 3, 2018 at 17:35

Jim Garrison · Accepted Answer · 2019-02-05 18:39:23Z

5

You are using eval() which, as you can probably guess, attempts to evaluate the expression.

The NashornScriptEngine implements javax.script.Compilable so it provides a compile() method. To use it you would have to cast engine to NashornScriptEngine, as in

NashornScriptEngine engine = (NashornScriptEngine) new ScriptEngineManager().getEngineByName("nashorn");

You get a ScriptException if compilation fails.

edited Feb 5, 2019 at 18:39

answered Aug 3, 2018 at 17:37

Jim Garrison

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3 Comments

apocalypz Over a year ago

No there is not such method. Why is this accepted answer ?

Jim Garrison Over a year ago

@kasper Actually, the Nashorn script engine does implement Compilable, so it does have a compile() method. I agree this is not obvious in the example provided by the OP, as engine would need to be casted to NashornScriptEngine to work. I've updated the answer. Thanks.

kasvith Over a year ago

yeah, that seems true after your answer i also looked into it. We can use something like compilable = (Compilable) scriptEngine; compilable.compile(script);. Thanks for update on answer

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