mapreduce读取hbase中表的数据，直接打印或者回传数据到hbase数据库表

package com.syyz.zjs;

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 ExampleTotalMapReduce{
public static void main(String[] args) {
try{
Configuration config = HBaseConfiguration.create();
config.set("hbase.zookeeper.quorum", "node7,node8,node9");
Job job = new Job(config,"ExampleSummary");
job.setJarByClass(ExampleTotalMapReduce.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(
"t_cdr3",        // 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(
"t_cdr",        // 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!");
}
} catch(Exception e){
e.printStackTrace();
}
}

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 {
//取了表中一个datetime的字段
String datetime = new String(value.getValue(Bytes.toBytes("cf1"), Bytes.toBytes("datetime")));
text.set(datetime);
context.write(text, ONE);
}
}

//把取到的值直接打印了。。
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;
System.out.println(key+"*************");
//			for (IntWritable val : values) {
//				//sum += val.get();
//
//			}

//把结果输出到hbase中了
//			Put put = new Put(key.getBytes());
//			put.add(Bytes.toBytes("info"), Bytes.toBytes("count"), Bytes.toBytes(String.valueOf(sum)));
//
//			context.write(null, put);
}
}
}