Nashorn : how to evaluate scripts in scripting mode

Question

Im starting to explore jdk 8 new javascript engine nashorn and wanted to build some automating task scripts. I ve an issue, ive no idea how to evaluate a js file in scripting mode from javascript, using engine.eval() eg .

p.s: im not talking about jjs -scripting which is good but only works one way. I want the other way; make the engine evaluate in scripting mode from java

Answer 1

After a lot of head scratching, i came up with a trick where i can actually launch my script's execution through a command line from a hand crafted System Process :

//tricking the nashorn engine with jjs command
    public void evalScriptInScriptingMode(String fileName)
    {
        String[] args = new String[]{"jjs", "-scripting", fileName};

        //This class is used to create operating system processes
        ProcessBuilder pb = new ProcessBuilder(args);

        pb.directory(null);

        File log = new File("jjs_log.txt");

        int i = 0;

        while(log.exists())
        {
            i++;
            log = new File("jjs" + i + "_log.txt");
        }


        pb.redirectErrorStream(true);
        pb.redirectOutput(ProcessBuilder.Redirect.appendTo(log));
        Process p = null;

        try
        {
            p = pb.start();    //start the process which remains open
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
    }