How to call Nashorn from Java - windows

Question

I have a batfile that I want to call from java. I made a nashorn script, that runs successfully from commandline and from Netbeans 'run' command. Here it is:
#!C:/Program Files/Java/jdk1.8.0_25/bin -fv
$ENV.PWD = 'C:/Hydromodel/MapGenerate';
$EXEC("cmd /c start cmd_all.bat");
print ('finished!');
I try to call the script from java this way:
public class RunCmd {
public void nashornTest() {
ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
try {
Object eval = engine.eval("load('src/simple/a_test.js');");
//Object eval = engine.eval(new FileReader("C:/_Udvikling/Maven/realtid_2014/src/main/java/simple/a_test.js"));
} catch (Exception ex ) {
Logger.getLogger(CmdTest.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
Both ways I get this error:
Severe: javax.script.ScriptException: TypeError: Cannot load script from src/simple/a_test.js in <eval> at line number 1
Even if the javascript file is reduced to:
print ('hello!');
I also tried this SO proposed way
The Error stays.
I googled, but most people seem to use Linux or Mac when writing about Nashorn.
Should I do anything special to call Nashorn from java on a Windows box?
mbwiese
I am running Netbeans 8 and JDK 8 with Glassfish 4.1 on Windows 7