HBaseTest.java

import java.io.IOException;
import java.util.HashMap;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.client.ResultScanner;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.client.Table;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class HBaseTest extends Configured implements Tool {
    public static final String TABLE_NAME = "tab";
    private static final String COLUMN_FAMILY = "col";
    private static final byte[] QUALIFIER = Bytes.toBytes("1");

    public static class Map extends Mapper<LongWritable, Text, Text, DoubleWritable> {
        @Override
        protected void setup(Context context) throws IOException, InterruptedException {
            Configuration config = HBaseConfiguration.create();
            Connection conn = ConnectionFactory.createConnection(config);
            Table table = conn.getTable(TableName.valueOf(TABLE_NAME));
            Scan scan = new Scan();
            scan.addColumn(Bytes.toBytes(COLUMN_FAMILY), QUALIFIER);
            ResultScanner scanner = table.getScanner(scan);
            scanner.close();
            table.close();
        }

        @Override
        public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        context.write(new Text("a"), new DoubleWritable(1.5));
        }
    }

    @Override
    public int run(String[] args) throws Exception {
        Job job = Job.getInstance(getConf(), "HBaseTest");
        job.setJarByClass(HBaseTest.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(DoubleWritable.class);

        job.setMapperClass(Map.class);

        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);

        job.waitForCompletion(true);
        return 0;
    }

    public static void main(String[] args) throws Exception {
        int ret = ToolRunner.run(new Configuration(), new MemoryBackedJoinHBase(), args);
        System.exit(ret);
    }
}