hbase->Mapreduce->hbase

Hbase对Mapreduce API进行了扩展，方便Mapreduce任务读写HTable数据。

package taglib.customer;import java.io.IOException;  import org.apache.hadoop.conf.Configuration;  import org.apache.hadoop.hbase.HBaseConfiguration;  import org.apache.hadoop.hbase.client.Put;  import org.apache.hadoop.hbase.client.Result;  import org.apache.hadoop.hbase.client.Scan;  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;  import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;  import org.apache.hadoop.hbase.mapreduce.TableMapper;  import org.apache.hadoop.hbase.mapreduce.TableReducer;  import org.apache.hadoop.hbase.util.Bytes;  import org.apache.hadoop.io.IntWritable;  import org.apache.hadoop.io.Text;  import org.apache.hadoop.mapreduce.Job;public class MrHbase {public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {// TODO Auto-generated method stubConfiguration conf = HBaseConfiguration.create();  conf.set("hbase.zookeeper.quorum", "192.168.58.101");        Job job = new Job(conf,"ExampleSummary");          job.setJarByClass(MrHbase.class);     // class that contains mapper and reducer          Scan scan = new Scan();          scan.setCaching(500);        // 1 is the default in Scan, which will be bad for MapReduce jobs          scan.setCacheBlocks(false);  // don't set to true for MR jobs          // set other scan attrs          //scan.addColumn(family, qualifier);          TableMapReduceUtil.initTableMapperJob(                  "blog",        // input table                  scan,               // Scan instance to control CF and attribute selection                  MyMapper.class,     // mapper class                  Text.class,         // mapper output key                  IntWritable.class,  // mapper output value                  job);          TableMapReduceUtil.initTableReducerJob(                  "blog2",        // output table                  MyTableReducer.class,    // reducer class                  job);          job.setNumReduceTasks(1);   // at least one, adjust as required          boolean b = job.waitForCompletion(true);          if (!b) {              throw new IOException("error with job!");          }}public static class MyMapper extends TableMapper<Text, IntWritable>  {            private final IntWritable ONE = new IntWritable(1);          private Text text = new Text();            public void map(ImmutableBytesWritable row, Result value, Context context) throws IOException, InterruptedException {              String ip = Bytes.toString(row.get());              String url = new String(value.getValue(Bytes.toBytes("article"), Bytes.toBytes("title")));              text.set(ip+"&"+url);              context.write(text, ONE);          }      }public static class MyTableReducer extends TableReducer<Text, IntWritable, ImmutableBytesWritable>  {          public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {              int sum = 0;              for (IntWritable val : values) {                  sum += val.get();              }                Put put = new Put(key.getBytes());              put.add(Bytes.toBytes("article"), Bytes.toBytes("title"), Bytes.toBytes(String.valueOf(sum)));                context.write(null, put);          }      }  }