readFully not defined with Java Nashorn Javascript Engine

Question

I am trying to run a javascript script with the new Java 8 Nashorn javascript engine but it fails with the following error:

<eval>:1 ReferenceError: "readFully" is not defined

The script uses the readFully function that should be defined in the global scope nashorn is run with the scripting mode enabled (wich is default when running through a ScriptEngine as seen here http://mail.openjdk.java.net/pipermail/nashorn-dev/2013-December/002562.html).

Here is a sample to reproduce the error:

import java.io.FileNotFoundException;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class Test {

    public static void main(String[] argv) throws FileNotFoundException, ScriptException {
        ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByName("nashorn");

        scriptEngine.eval("print('Hey!');print(print);print(readFully);");


    }
}

This sample prints Hey ! and then the source code of the print function (another nashorn built-in function) and finally it should print the source code of the readFully method. But I have this Exception instead:

Exception in thread "main" javax.script.ScriptException: ReferenceError: "readFully" is not defined in <eval> at line number 1
    at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:586)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:570)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:525)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:521)
    at jdk.nashorn.api.scripting.NashornScriptEngine.eval(NashornScriptEngine.java:192)
    at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
    at com.github.bringking.maven.requirejs.Test.main(Test.java:14)
Caused by: <eval>:1 ReferenceError: "readFully" is not defined
    at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:58)
    at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:320)
    at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:292)
    at jdk.nashorn.api.scripting.NashornScriptEngine.__noSuchProperty__(NashornScriptEngine.java:272)
    at jdk.nashorn.internal.scripts.Script$engine.L:35(nashorn:engine/resources/engine.js:37)
    at jdk.nashorn.internal.scripts.Script$\^eval\_.runScript(<eval>:1)
    at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:535)
    at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:209)
    at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:378)
    at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:568)
    ... 5 more

When the sample script is run with the nashorn command line with the -scripting parameter (with the jjs tool of the jdk), all is fine. Here is the result of the same script:

Hey!
function print() { [native code] }
function readFully() { [native code] }

I could rewrite a readFully method and bind it with the script context, but I prefer to understand why it does not work and use already built-in functions.

Regards

Orcale JDK on Windows 7: java version "1.8.0_25", Java(TM) SE Runtime Environment (build 1.8.0_25-b18), Java HotSpot(TM) Client VM (build 25.25-b02, mixed mode) — Stratehm
– Stratehm, Commented Jan 5, 2015 at 22:02
The blog post you linked to is re: openjdk. They're still a bit different. — Elliott Frisch
– Elliott Frisch, Commented Jan 5, 2015 at 22:04
Indeed. 1 point. So, now I am looking for a way to programmatically "force" the scripting mode of Nashorn :) — Stratehm
– Stratehm, Commented Jan 5, 2015 at 22:09
Not sure. But your engine should probable be javascript (not nashorn) --- what if they rename it in Java 9? — Elliott Frisch
– Elliott Frisch, Commented Jan 5, 2015 at 22:11

Stratehm · Accepted Answer · 2015-01-06 16:06:23Z

5

Finally, I have implemented a readFully function that I use in my script (Only compatible with Nashorn):

function readFully(url) {
    var result = "";
    var imports = new JavaImporter(java.net, java.lang, java.io);

    with (imports) {

        var urlObj = null;

        try {
            urlObj = new URL(url);
        } catch (e) {
            // If the URL cannot be built, assume it is a file path.
            urlObj = new URL(new File(url).toURI().toURL());
        }

        var reader = new BufferedReader(new InputStreamReader(urlObj.openStream()));

        var line = reader.readLine();
        while (line != null) {
            result += line + "\n";
            line = reader.readLine();
        }

        reader.close();
    }

    return result;
}

answered Jan 6, 2015 at 16:06

Stratehm

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Community · Accepted Answer · 2017-05-23 12:00:10Z

2

readFully is not a standard JavaScript function and it is likely not standard in Nashorn either.

There were similar issues when Rhino was chosen for inclusion in the Sun implementation of Java 6. The scripting tool may provide enhancements that are not present in the embedded API. readFully is not a documented function in the Java 8 Nashorn API.

In previous versions of Java the specification stated that provided scripting engines were an implementation detail of the JRE vendor. I am not aware if Java 8 makes anything about the engines provided mandatory or whether it makes any future compatibility guarantees. I would check JSR-337 thoroughly if this was likely to be an issue.

edited May 23, 2017 at 12:00

CommunityBot

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answered Jan 5, 2015 at 22:18

McDowell

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1 Comment

Stratehm Over a year ago

Thanks for the info. I will implement a readFully function by myself.

wickund · Accepted Answer · 2015-01-06 13:02:05Z

1

https://wiki.openjdk.java.net/display/Nashorn/Nashorn+extensions

readFully (-scripting mode only)

This function reads the entire contents of a file passed in as a string argument and sends it to stdout, or you can assign the result to a variable.

readFully example:

jjs> readFully("text.txt") This is the contents of the text.txt file located in the current working directory.

answered Jan 6, 2015 at 13:02

wickund

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3 Comments

Stratehm Over a year ago

My problem is that readFully is not defined when running through the ScriptEngine API. Not with the jjs executable (this way, all is fine).

wickund Over a year ago

You can pass options to Nashorn using the direct nashorn interface NashornScriptEngineFactory factory = new NashornScriptEngineFactory(); String[] options = new String[] { "—scripting" }; NashornScriptEngine engine = factory.getScriptEngine(options); or simply put a '#' as the first character of the script.

Volker Simonis Over a year ago

You can actually set/reset the option through a system property programmatically with System.setProperty("nashorn.args", "-scripting") which will give you the best of both worlds: you can stick to the javax.script API and you can still control the option per engine". Also see stackoverflow.com/questions/26873201/…

mtuulu · Accepted Answer · 2017-06-08 14:03:07Z

0

readFully is enabled only in scripting mode. Nashorn docs

try this:

>>jjs -scripting
jjs> readFully("your_file")

answered Jun 8, 2017 at 14:03

mtuulu

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Comments

srlgrg · Accepted Answer · 2019-11-02 11:48:16Z

0

readFully() function is only available as built in function in nashorgn when you enable scripting in you application There are two ways you can do this:-

pass -Dnashorn.args=-scripting when you run your application to enable nashorn scripting

Enable it programmatically by creating Nashorn engine with scripting args

NashornScriptEngineFactory factory = new NashornScriptEngineFactory();
ScriptEngine engine = factory.getScriptEngine(new String[] { "-scripting" });

answered Nov 2, 2019 at 11:48

srlgrg

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