An example of a generating input format for map/reduce jobs with no hard coded input

gistfile1.txt

   /**
   * An input split that generates (firstname lastname product) tuples.
   * These simulate transactions at a pet store by clients.
   * First iteration of the BigPetStore blueprint project.
   */
	public static class TransactionGeneratorInputFormat extends
			FileInputFormat<Text,Text> {
		static final Integer TRANSACTIONS = 100;

		static String[] FIRSTNAMES = new String[]{
			"jay",
			"john",
			"jim",
			"diana",
			"duane",
			"david",
			"peter",
			"paul",
			"matthias",
			"hyacinth",
			"jacob",
			"andrew",
			"andy",
			"mischa",
			"enno",
			"sanford",
			"shawn"
		};
		static String[] LASTNAMES = new String[]{
			"vyas",
			"macleroy",
			"watt",
			"childress",
			"shaposhnick",
			"bukatov",
			"govind",
			"jones",
			"stevens",
			"yang",
			"fu",
			"ghandi",
			"watson",
			"walbright",
			"samuelson"
		};
		static String[] PRODUCTS = new String[]{
			"dog food",
			"cat food",
			"fish food",
			"little chew toy",
			"big chew toy",
			"dog treats (hard)",
			"dog treats (soft)",
			"premium dog food",
			"premium cat food",
			"pet deterrent",
			"flea collar",
			"turtle food",
		};
		
		@Override
		public RecordReader<Text, Text> createRecordReader(
				InputSplit arg0, TaskAttemptContext arg1) throws IOException,
				InterruptedException {
			// TODO Auto-generated method stub
			return new RecordReader() {
				@Override
				public void close() throws IOException {

				}
				Text name, transaction;
				Random r = new Random();
				@Override
				public Text getCurrentKey() throws IOException,
						InterruptedException {
					// TODO Auto-generated method stub
					return name;				
				}

				@Override
				public Text getCurrentValue() throws IOException,
						InterruptedException {
					// TODO Auto-generated method stub
					return transaction;
				}

				@Override
				public void initialize(InputSplit arg0, TaskAttemptContext arg1)
						throws IOException, InterruptedException {
				}
				int soFar=0;
				@Override
				public boolean nextKeyValue() throws IOException,
						InterruptedException {
					name=new Text(FIRSTNAMES[r.nextInt(FIRSTNAMES.length-1)]+"_"+LASTNAMES[r.nextInt(LASTNAMES.length-1)]);
					transaction=new Text(PRODUCTS[r.nextInt(PRODUCTS.length-1)]);
					
					//continue returning a new mock transaction
					//until we exceed the number of transactions.
					System.out.println(name + " " + transaction);
					return soFar++ < TRANSACTIONS;
				}

				@Override
				public float getProgress() throws IOException,
						InterruptedException {
					// TODO Auto-generated method stub
					return (float)soFar/(float)TRANSACTIONS;
				}

				
			};
		}

		@Override
		public List<InputSplit> getSplits(JobContext arg) throws IOException {
			int transactionsPerSplit = arg.getConfiguration().getInt("transactions",10);
			int splits = arg.getConfiguration().getInt("transaction_files",2);
			
			List<InputSplit> l = Lists.newArrayList();
			for(int i = 0 ; i < splits ; i++){
				log.info(i+ " Adding a new input split of size " + transactionsPerSplit);
				l.add(new PetStoreTransactionGeneratorJob.TransactionInputSplit(/*transactionsPerSplit*/));
			}
			return l;
		}

	}
	public static class TransactionInputSplit extends InputSplit implements Writable {

		public void readFields(DataInput arg0) throws IOException {
		}

		public void write(DataOutput arg0) throws IOException {
		}

		@Override
		public String[] getLocations() throws IOException, InterruptedException {
			return new String[] {};
		}

		@Override
		public long getLength() throws IOException, InterruptedException {
			return 100;
		}
}