davidflanagan.com/javascript5

import javax.script.*;
import java.io.*;

// Evaluate a file of JavaScript and print its result
public class RunScript {
    public static void main(String[] args) throws IOException {
        // Obtain an interpreter or "ScriptEngine" to run the script.
        ScriptEngineManager scriptManager = new ScriptEngineManager();
        ScriptEngine js = scriptManager.getEngineByExtension("js");

        // The script file we are going to run
        String filename = null;

        // A Bindings object is a symbol table for or namespace for the
        // script engine.  It associates names and values and makes
        // them available to the script.
        Bindings bindings = js.createBindings();

        // Process the arguments. They may include any number of 
        // -Dname=value arguments, which define variables for the script.
        // Any argument that does not begin with -D is taken as a filename
        for(int i = 0; i < args.length; i++) {
            String arg = args[i];
            if (arg.startsWith("-D")) {
                int pos = arg.indexOf('=');
                if (pos == -1) usage();
                String name = arg.substring(2, pos);
                String value = arg.substring(pos+1);
                // Note that all the variables we define are strings.
                // Scripts can convert them to other types if necessary.
                // We could also pass a java.lang.Number, a java.lang.Boolean
                // or any Java object or null.
                bindings.put(name, value);
            }
            else {
                if (filename != null) usage(); // only one file please
                filename = arg;
            }
        }
        // Make sure we got a file out of the arguments.
        if (filename == null) usage();

        // Add one more binding using a special reserved variable name
        // to tell the script engine the name of the file it will be executing.
        // This allows it to provide better error messages.
        bindings.put(ScriptEngine.FILENAME, filename);

        // Get a stream to read the script.
        Reader in = new FileReader(filename);

        try {
            // Evaluate the script using the bindings and get its result.
            Object result = js.eval(in, bindings);

            // Display the result.
            System.out.println(result);
        }
        catch(ScriptException ex) {
            // Or display an error message.
            System.out.println(ex);
        }
    }

    static void usage() {
        System.err.println(
                 "Usage: java RunScript [-Dname=value...] script.js");
        System.exit(1);
    }
}