source: sample/WordCountIntoHBase.java @ 8

/**
 * Program: WordCountIntoHBase.java
 * Editor: Waue Chen 
 * From :  NCHC. Taiwn
 * Last Update Date: 06/10/2008
 */

/**
 * Purpose : 
 *  Store every line from $Input_Path to HBase
 * 
 * HowToUse : 
 *  Make sure Hadoop file system and HBase are running correctly.
 *  Use Hadoop instruction to add input-text-files to $Input_Path.
 *  ($ bin/hadoop dfs -put local_dir hdfs_dir)
 *  Then run the program with BuildHTable.java after \
 *  modifying these setup parameters.
 * 
 * Check Result : 
 *  View the result by hbase instruction (hql> select * from $Table_Name). 
 *  Or run WordCountFromHBase.java then inspect http://localhost:60070 by web explorer;
 */

package tw.org.nchc.code;

import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapred.TableReduce;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.MapWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.lib.IdentityMapper;
import org.apache.hadoop.mapred.lib.IdentityReducer;

public class WordCountIntoHBase {

  /* setup parameters */
  // $Input_Path. Please make sure the path is correct and contains input files
  static final String Input_Path = "/user/waue/simple";
  // Hbase table name, the program will create it
  static final String Table_Name = "word_count5";
  // column name, the program will create it
  static final String colstr = "word:text" ;
  
  // constructor
  private WordCountIntoHBase() {
  }

  private static class ReduceClass extends TableReduce<LongWritable, Text> {
    // set (column_family:column_qualify)
    private static final Text col = new Text(WordCountIntoHBase.colstr);
    // this map holds the columns per row
    private MapWritable map = new MapWritable();
    public void reduce(LongWritable key, Iterator<Text> values,
        OutputCollector<Text, MapWritable> output, Reporter reporter)
        throws IOException {
      // contents must be ImmutableBytesWritable
      ImmutableBytesWritable bytes = 
        new ImmutableBytesWritable(values.next().getBytes());     
      map.clear();
      // write data 
      map.put(col, bytes);
      // add the row with the key as the row id
      output.collect(new Text(key.toString()), map);
    }
  }

  /**
   * Runs the demo.
   */
  public static void main(String[] args) throws IOException { 
    // parse colstr to split column family and column qualify
    String tmp[] = colstr.split(":");
    String Column_Family = tmp[0]+":";
    String CF[] = {Column_Family};
    // check whether create table or not , we don't admit \ 
    // the same name but different structure
    BuildHTable build_table = new BuildHTable(Table_Name,CF);
    if (!build_table.checkTableExist(Table_Name)) {
      if (!build_table.createTable()) {
        System.out.println("create table error !");
      }
    }else{
      System.out.println("Table \"" + Table_Name +"\" has already existed !");
    }
    int mapTasks = 1;
    int reduceTasks = 1;
    JobConf conf = new JobConf(WordCountIntoHBase.class);
    conf.setJobName(Table_Name);

    // must initialize the TableReduce before running job
    TableReduce.initJob(Table_Name, ReduceClass.class, conf);
    conf.setNumMapTasks(mapTasks);
    conf.setNumReduceTasks(reduceTasks);
    conf.setInputPath(new Path(Input_Path));
    conf.setMapperClass(IdentityMapper.class);
    conf.setCombinerClass(IdentityReducer.class);
    conf.setReducerClass(ReduceClass.class);

    JobClient.runJob(conf);
  }
}