Java 8 example: call between Java and Javascript

This example show how to call Javascript function from Java, and call Java method from Javascript.

JavaTryJavaScript.java

package javatryjavascript;

import java.io.FileNotFoundException;
import java.io.FileReader;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class JavaTryJavaScript {
    
    final static String myJavascript = "/home/pi/testJS/newjavascript.js";

    public static void main(String[] args) 
            throws FileNotFoundException, ScriptException, NoSuchMethodException {
        ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
        ScriptEngine nashornEngine = scriptEngineManager.getEngineByName("nashorn");
        
        FileReader fileReader = new FileReader(myJavascript);
        nashornEngine.eval(fileReader);
        
        Invocable invocable = (Invocable)nashornEngine;
        invocable.invokeFunction("testJavaScript1", "Hello from Java");
        
    }
    
    public static void JavaCalledFromJS(String s){
        System.out.println("Java method called from JavaScript: " + s);
    }
    
}

The Javascript in a separated file, /home/pi/testJS/newjavascript.js

var testJavaScript1 = function(a){
    print('testJavaScript1, called from Java: ' + a);
    testJavaScript2();
    return;
}

var testJavaScript2 = function(){
    print('testJavaScript2');
    var javaClass = Java.type("javatryjavascript.JavaTryJavaScript");
    javaClass.JavaCalledFromJS("message from JavaScript");
    return;
}