original code

gistfile1.txt

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package org.docpresso.templating;

import org.docpresso.util.Tuples.Pair;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.ScriptableObject;
import org.mozilla.javascript.annotations.JSFunction;

/**
 *
 * @author Kay
 */
public class TemplateScope extends ScriptableObject {

    private StringBuilder log = new StringBuilder();
    private StringBuilder out = new StringBuilder();

    private TemplateScope() {
        //context.initStandardObjects(this);
    }

    public static TemplateScope init(Context context) {
        TemplateScope t = new TemplateScope();
        context.initStandardObjects(t);
        JSFunctions.init(t);
        return t;
    }

    @Override
    public String getClassName() {
        return "TemplateScope";
    }

    public Pair<String, String> pullOutput() {
        String out_str = out.toString();
        out.setLength(0);
        String log_str = log.toString();
        log.setLength(0);
        return new Pair(out_str, log_str);
    }

    /**
     * Defines the JSfunction which modify the TemplateScope
     */
    private static class JSFunctions {

        public static final String[] METHODS =
                new String[]{"print", "log", "printLine", "logLine"};

        public static void init(TemplateScope ts) {
            int modifiers = ScriptableObject.READONLY | ScriptableObject.PERMANENT | ScriptableObject.CONST;
            ts.defineFunctionProperties(JSFunctions.METHODS, JSFunctions.class, modifiers);
        }

        public static void print(Context cx, Scriptable thisObj, Object[] args,
                Function funObj) {
            TemplateScope self = (TemplateScope) thisObj;
            for (Object arg : args) {
                self.out.append(arg.toString());
            }
        }

        public static void printLine(Context cx, Scriptable thisObj, Object[] args,
                Function funObj) {
            TemplateScope self = (TemplateScope) thisObj;
            for (Object arg : args) {
                self.out.append(arg.toString());
            }
            self.out.append("\n");
        }

        public static void log(Context cx, Scriptable thisObj, Object[] args,
                Function funObj) {
            TemplateScope self = (TemplateScope) thisObj;
            for (Object arg : args) {
                self.log.append(arg.toString());
            }
        }

        public static void logLine(Context cx, Scriptable thisObj, Object[] args,
                Function funObj) {
            TemplateScope self = (TemplateScope) thisObj;
            for (Object arg : args) {
                self.log.append(arg.toString());
            }
            self.log.append("\n");
        }
    }

    public static void main(String... args) {
        Context context;
        try {
            context = Context.enter();
            TemplateScope scope = TemplateScope.init(context);
            context.evaluateString(scope, "print(\"hallo\",' ' ,'wereld!'); log(\"tralala\");", "test source", 1, null);
            Pair<String, String> result = scope.pullOutput();
            System.out.println("out is: " + result.a);
            System.out.println("log is: " + result.b);
            result = scope.pullOutput();
            System.out.println("out is: " + result.a);
            System.out.println("log is: " + result.b);
            context.evaluateString(scope, "log(\"test\" + \"\\n\");", "test source", 1, null);
            result = scope.pullOutput();
            System.out.println("out is: " + result.a);
            System.out.println("log is: " + result.b);
        } finally {
            Context.exit();
        }

    }
}