hadoop map reduce job with HDFS input and HBASE output

Question

I'm new on hadoop. I have a MapReduce job which is supposed to get an input from Hdfs and write the output of the reducer to Hbase. I haven't found any good example.

Here's the code, the error runing this example is Type mismatch in map, expected ImmutableBytesWritable recieved IntWritable.

Mapper Class

public static class AddValueMapper extends Mapper < LongWritable,
 Text, ImmutableBytesWritable, IntWritable > {  

  /* input <key, line number : value, full line>
   *  output <key, log key : value >*/  
public void map(LongWritable key, Text value, 
     Context context)throws IOException, 
     InterruptedException {
  byte[] key;
  int value, pos = 0;
  String line = value.toString();
  String p1 , p2 = null;
  pos = line.indexOf("=");

   //Key part
   p1 = line.substring(0, pos);
   p1 = p1.trim();
   key = Bytes.toBytes(p1);   

   //Value part
   p2 = line.substring(pos +1);
   p2 = p2.trim();
   value = Integer.parseInt(p2);

   context.write(new ImmutableBytesWritable(key),new IntWritable(value));
  }
}

Reducer Class

public static class AddValuesReducer extends TableReducer<
  ImmutableBytesWritable, IntWritable, ImmutableBytesWritable> {

  public void reduce(ImmutableBytesWritable key, Iterable<IntWritable> values, 
   Context context) throws IOException, InterruptedException {

         long total =0;
         // Loop values
         while(values.iterator().hasNext()){
           total += values.iterator().next().get();
         }
         // Put to HBase
         Put put = new Put(key.get());
         put.add(Bytes.toBytes("data"), Bytes.toBytes("total"),
           Bytes.toBytes(total));
         Bytes.toInt(key.get()), total));
            context.write(key, put);
        }
    }

I had a similar job only with HDFS and works fine.

Edited 18-06-2013. The college project finished successfully two years ago. For job configuration (driver part) check correct answer.

Answer 1

Here is the code which will solve your problem

---

---

Driver

HBaseConfiguration conf =  HBaseConfiguration.create();
Job job = new Job(conf,"JOB_NAME");
    job.setJarByClass(yourclass.class);
    job.setMapperClass(yourMapper.class);
    job.setMapOutputKeyClass(Text.class);
    job.setMapOutputValueClass(Intwritable.class);
    FileInputFormat.setInputPaths(job, new Path(inputPath));
    TableMapReduceUtil.initTableReducerJob(TABLE,
            yourReducer.class, job);
    job.setReducerClass(yourReducer.class);
            job.waitForCompletion(true);

---

---

Mapper&Reducer

class yourMapper extends Mapper<LongWritable, Text, Text,IntWritable> {
//@overide map()
 }

---

class yourReducer
        extends
        TableReducer<Text, IntWritable, 
        ImmutableBytesWritable>
{
//@override reduce()
}

---

Answer 2

Not sure why the HDFS version works: normaly you have to set the input format for the job, and FileInputFormat is an abstract class. Perhaps you left some lines out? such as

job.setInputFormatClass(TextInputFormat.class);