Overriding RecordReader to read Paragraph at once instead of line

Question

I am overriding method "next" of RecordReader class and "getRecordReader" of TextInputFormat class in order to send a whole paragraph to the mapper instead of line by line. (I am using old api's and defination for my paragraph is append till the time a blank line comes in my text file.)
Below is my code:

public class NLinesInputFormat extends TextInputFormat  
{  
   @Override
   public RecordReader<LongWritable, Text> getRecordReader(InputSplit split, JobConf conf, Reporter reporter)throws IOException     {   
        reporter.setStatus(split.toString());  
        return new ParagraphRecordReader(conf, (FileSplit)split);
    }
}



public class ParagraphRecordReader implements RecordReader<LongWritable, Text> 
{
        private LineRecordReader lineRecord;
        private LongWritable lineKey;
        private Text lineValue;
        public ParagraphRecordReader(JobConf conf, FileSplit split) throws IOException {
            lineRecord = new LineRecordReader(conf, split);
            lineKey = lineRecord.createKey();
            lineValue = lineRecord.createValue();
        }

        @Override
        public void close() throws IOException {
            lineRecord.close();
        }

        @Override
        public LongWritable createKey() {
            return new LongWritable();

        }

        @Override
        public Text createValue() {
            return new Text("");

        }

        @Override
        public float getProgress() throws IOException {
            return lineRecord.getPos();

        }

        @Override
        public synchronized boolean next(LongWritable key, Text value) throws IOException {
            boolean appended, gotsomething;
            boolean retval;
            byte space[] = {' '};
            value.clear();
            gotsomething = false;
            do {
                appended = false;
                retval = lineRecord.next(lineKey, lineValue);
                if (retval) {
                    if (lineValue.toString().length() > 0) {
                        byte[] rawline = lineValue.getBytes();
                        int rawlinelen = lineValue.getLength();
                        value.append(rawline, 0, rawlinelen);
                        value.append(space, 0, 1);
                        appended = true;
                    }
                    gotsomething = true;
                }
            } while (appended);

            //System.out.println("ParagraphRecordReader::next() returns "+gotsomething+" after setting value to: ["+value.toString()+"]");
            return gotsomething;
        }

        @Override
        public long getPos() throws IOException {
            return lineRecord.getPos();
        }
    }  

Questions:
1. I did not find any concrete guide on how to do this, so may be there is something I am doing wrong please comment any suggestion?
2. I am able to compile this correctly but when I run my job my mapper is continuously running and I am not able to figure it out where is the problem?

Answer 1

Your code works perfectly fine for me. The only change I did was to have these classes as inner class and made them static.

Input file was as follows:

This is awesome.
WTF is this.

This is just a test.

The mapper code looked like:

@Override
public void map(LongWritable key, Text value, OutputCollector<Text, Text> output, Reporter reporter)
    throws IOException {

    System.out.println(key+" : "+value);
}

And the output was:

0 : This is awesome. WTF is this. 
0 : This is just a test.

I am sure you would haven't forgotten to set the input format, but just in case, set it as follows:

conf.setInputFormat(NLinesInputFormat.class);