MapReduce操作Hbase --table2file

官方手册：http://hbase.apache.org/book.html#mapreduce.example

简单的操作，将hbase表中的数据写入到文件中。

RunJob 源码：

 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.HBaseConfiguration;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.mapreduce.TableInputFormat;
 import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.mapreduce.Job;
 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;

 /**
  * Created by Edward on 2016/6/29.
  */
 public class RunJob implements Tool {

     private Configuration conf = null;

     @Override
     public int run(String[] strings) throws Exception {

         Configuration conf = this.getConf();

         FileSystem fs = FileSystem.get(conf);

         Job job = Job.getInstance(conf,"etl");
         job.setJarByClass(RunJob.class);

         job.setInputFormatClass(TableInputFormat.class);
         job.setOutputFormatClass(TextOutputFormat.class);
         job.setOutputKeyClass(TextOutputFormat.class);

         Scan scan = new Scan();
         scan.setCaching(1024);
         scan.setCacheBlocks(false);

         TableMapReduceUtil.initTableMapperJob("test1",
                 scan,
                 MyMapper.class,
                 Text.class,
                 Text.class,
                 job);

         Path path = new Path("/hbase_out");
         if(fs.exists(path))
         {
             fs.delete(path,true);
         }

         FileOutputFormat.setOutputPath(job, new Path("/hbase_out"));

         boolean b = job.waitForCompletion(true);
         if(b)
         {
             System.out.println("执行成功");
         }
         return 0;
     }

     @Override
     public void setConf(Configuration configuration) {

         System.setProperty("HADOOP_USER_NAME","root");
         configuration.set("hbase.zookeeper.quorum","node1,node2,node3");
         configuration.set("mapred.jar","D:\\etl.jar");

         this.conf = HBaseConfiguration.create(configuration);
     }

     @Override
     public Configuration getConf() {
         return this.conf;
     }

     public static void main(String[] args)
     {
         try {
             ToolRunner.run(new Configuration(), new RunJob(), args);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 }

MyMapper代码：

 import org.apache.hadoop.hbase.client.Result;
 import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
 import org.apache.hadoop.hbase.mapreduce.TableMapper;
 import org.apache.hadoop.io.Text;

 import java.io.IOException;

 /**
  * Created by Edward on 2016/6/29.
  */
 public class MyMapper extends TableMapper<Text, Text>{
     @Override
     protected void map(ImmutableBytesWritable key, Result value, Context context) throws IOException, InterruptedException {

         String val = new String(value.getValue("info".getBytes(),"name".getBytes()));
         String row = new String(value.getRow());
         context.write(new Text(row), new Text(val));
     }
 }

MyReducer代码：

 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.mapreduce.Reducer;

 import java.io.IOException;

 /**
  * Created by Edward on 2016/6/29.
  */
 public class MyReducer extends Reducer<Text,Text,Text,Text>{

     @Override
     protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
         for(Text t:values) {
             context.write(key, t);
         }
     }
 }