Type mismatch in value from map: expected org.apache.hadoop.io.NullWritable, recieved org.apache.hadoop.io.Text

I am trying to tweak an existing problem to suit my needs..

Basically input is simple text I process it and pass key/value pair to reducer And I create a json.. so there is key but no value So mapper:

Input: Text/Text

Output: Text/Text

Reducer: Text/Text

Output: Text/None

My signatures are as follows:

public class AdvanceCounter {
/**
 * The map class of WordCount.
 */
public static class TokenCounterMapper
    extends Mapper<Object, Text, Text, Text> { // <--- See this signature

   public void map(Object key, Text value, Context context) // <--- See this signature
        throws IOException, InterruptedException {

     context.write(key,value); //both are of type text OUTPUT TO REDUCER
    }
}
   public static class TokenCounterReducer
    extends Reducer<Text, Text, Text, **NullWritable**> { // <--- See this signature Nullwritable here
    public void reduce(Text key, Iterable<Text> values, Context context) // <--- See this signature
        throws IOException, InterruptedException {


        for (Text value : values) {
            JSONObject jsn = new JSONObject();
            //String output = "";
            String[] vals = value.toString().split("\t");
            String[] targetNodes = vals[0].toString().split(",",-1);
            try {
                jsn.put("source",vals[1]);
                jsn.put("targets",targetNodes);
                context.write(new Text(jsn.toString()),null); // no value 
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }


    }
}
public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
    String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
    Job job = new Job(conf, "Example Hadoop 0.20.1 WordCount");

    // ...
    //
    job.setOutputValueClass(NullWritab