CODEWITHSUNDEEP
javascriptjavaarraysnashorn
Rahul Choubey
Rahul Choubey

Reputation: 41

How can I get javascript array output in java (in array)?

I have a javascript file fun.js

function fun1(){
    var arr =['This','is','from','js'];
    return arr;
}

I want to get this array in java array so I used nashorn as-

try{
    ScriptEngine engine= new ScriptEngineManager().getEngineByName("nashorn");
    engine.eval(new FileReader("fun.js"));
    Invocable invocable = (Invocable) engine;
    Object obj = (Object)invocable.invokeFunction("fun1");
    System.out.println(obj.toString());
}
catch(Exception e){
    e.printStackTrace();
}

But I am getting this output- [object Array]

How can I get this output as java array?

Upvotes: 0

Views: 2839

Answers (5)

A. Sundararajan
A. Sundararajan

Reputation: 4405

You can use methods of Nashorn specific extension object "Java" to convert between JavaScript and Java arrays.

See also: https://wiki.openjdk.java.net/display/Nashorn/Nashorn+extensions#Nashornextensions-java_to

Simple Example that invokes Java.to from Java code:

import javax.script.*;

public class Main {
    public static void main(String[] args) throws Exception {
        ScriptEngine e = new ScriptEngineManager().getEngineByName("nashorn");
        e.eval("function fun1() { return ['this', 'is', 'from', 'js']; }");
        Invocable invocable = (Invocable)e;
        Object obj = (Object)invocable.invokeFunction("fun1");
        // get "Java" api object
        Object Java = e.get("Java");
        // invoke Java.to function to convert JS array to Java String array
        String[] arr = (String[])invocable.invokeMethod(
            Java, "to", obj, "java.lang.String[]");
        // access String array
        for (String s : arr) { System.out.println(s); }
    }
}

Upvotes: 1

Harshita Sethi
Harshita Sethi

Reputation: 2125

The output what you'll get in Java will be in JsonArray format. So you can pass your input content in jsonArray and iterate over that JsonArray.

you can use jettison-1.3.jar as JSONAray library.

Here's what you can try.

String[] outputStr = new String[jsonArray.length()];
try {
    JSONArray jsonArray = new JSONArray(invocable.invokeFunction("fun1"));
    for (int i = 0; i < jsonArray.length(); i++) {
        outputStr[i] = jsonArray.getString(i);
    }
} catch(JSONException ex) {
    ex.printStackTrace();
}

For using org.json.simple.JSONArray import, you can use the following code

    String[] outputStr = new String[jsonArray.length()];
    try{
        JSONParser parser = new JSONParser();
        JSONArray jsonArray = (JSONArray) parser.parse(invocable.invokeFunction("fun1");

        for (int i = 0; i < jsonArray.size(); i++) {
            outputStr[i] = (String) jsonArray.get(i);
        }
    } catch(JSONException ex) {
        ex.printStackTrace();
    }

Upvotes: 0

MANOJ
MANOJ

Reputation: 736

public static void main(String[] args) throws JSONException, FileNotFoundException, ScriptException, NoSuchMethodException {

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

        engine.eval(new FileReader("C:\\Users\\Niku\\eclipse-workspace\\java_sample\\src\\test.js"));

        Invocable invocable = (Invocable) engine;
        Object obj = (Object)invocable.invokeFunction("fun1");
        Gson gson = new Gson();
        String k = gson.toJson(obj);
        JSONObject o = new JSONObject(k);
        System.out.println(o.getString("0"));
        System.out.println(o.getString("1"));
        System.out.println(o.getString("2"));
        System.out.println(o.getString("3"));

        Iterator x = o.keys();
        JSONArray jsonArray = new JSONArray();
        ArrayList<String> ar = new ArrayList<String>();
        while (x.hasNext()){
            String key = (String) x.next();
            ar.add(o.get(key).toString());
            jsonArray.put(o.get(key));
        }

        System.out.println(ar);
}

Iterating through the JsonObject can get you each element which can be added to another array to be used.

Upvotes: 2

MANOJ
MANOJ

Reputation: 736

I have tried recreating the scenario in java alone and was able to print the contents.

public class test {
    public static void main(String[] args) {
        String[] a = {"This","is","from","js"};
        Object obj = (Object) a;
        String stringArray = Arrays.deepToString((Object[]) obj);
        System.out.println(stringArray);
        String [] b =  stringArray.replaceAll("[\\[\\]]", "").split(",");
        System.out.println(b[0]);   
    }
}

Upvotes: 0

Ameya Pandilwar
Ameya Pandilwar

Reputation: 2778

The invokeFunction returns an instance of JSObject [jdk.nashorn.api.scripting.JSObject]

You could assign the response to a JSObject and then iterate over the values -

JSObject jsObject = null;
try {
    jsObject = (JSObject) invocable.invokeFunction("fun1");
    for (Object object : jsObject.values()) {
        System.out.println(object);
    }
} catch (NoSuchMethodException e) {
    ...
}

Upvotes: 0

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