简单实现CombineFileInputFormat

import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.Reducer.Context;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.CombineFileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.CombineFileRecordReader;
import org.apache.hadoop.mapreduce.lib.input.CombineFileSplit;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.lib.input.LineRecordReader;
import org.apache.hadoop.mapreduce.lib.input.SequenceFileRecordReader;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class TestCombine extends Configured implements Tool {
	private static class ProvinceMapper extends
			Mapper<Object, Text, Text, Text> {
		@Override
		protected void map(Object key, Text value, Context context)
				throws IOException, InterruptedException {
			System.out.println("value : " + value + " Context " + context);
			context.write(value, value);
		}
	}

	private static class ProvinceReducer extends
			Reducer<Text, Text, Text, Text> {
		@Override
		protected void reduce(Text key, Iterable<Text> values, Context context)
				throws IOException, InterruptedException {
			for (Text va : values) {
			    System.out.println("reduce " + key);
				context.write(key, key);
			}
		}
	}

	public static class CombineSequenceFileInputFormat<K, V> extends CombineFileInputFormat<K, V> {
	    @SuppressWarnings({ "unchecked", "rawtypes" })
	    @Override
	    public RecordReader<K, V> createRecordReader(InputSplit split, TaskAttemptContext context) throws IOException {
	        return new CombineFileRecordReader((CombineFileSplit)split, context, CombineLineRecordReader.class);
	    }
	}  

	public static class CombineLineRecordReader<K, V> extends RecordReader<K, V> {
	    private CombineFileSplit split;
	    private TaskAttemptContext context;
	    private int index;
	    private RecordReader<K, V> rr;  

	    @SuppressWarnings("unchecked")
	    public CombineLineRecordReader(CombineFileSplit split, TaskAttemptContext context, Integer index) throws IOException, InterruptedException {
	        this.index = index;
	        this.split = (CombineFileSplit) split;
	        this.context = context;  

	        this.rr = (RecordReader<K, V>) ReflectionUtils.newInstance(LineRecordReader.class, context.getConfiguration());
	    }  

	    @SuppressWarnings("unchecked")
	    @Override
	    public void initialize(InputSplit curSplit, TaskAttemptContext curContext) throws IOException, InterruptedException {
	        this.split = (CombineFileSplit) curSplit;
	        this.context = curContext;  

	        if (null == rr) {
	            rr = ReflectionUtils.newInstance(SequenceFileRecordReader.class, context.getConfiguration());
	        }  

	        FileSplit fileSplit = new FileSplit(this.split.getPath(index),
	                this.split.getOffset(index), this.split.getLength(index),
	                this.split.getLocations());  

	        this.rr.initialize(fileSplit, this.context);
	    }  

	    @Override
	    public float getProgress() throws IOException, InterruptedException {
	        return rr.getProgress();
	    }  

	    @Override
	    public void close() throws IOException {
	        if (null != rr) {
	            rr.close();
	            rr = null;
	        }
	    }  

	    @Override
	    public K getCurrentKey()
	    throws IOException, InterruptedException {
	        return rr.getCurrentKey();
	    }  

	    @Override
	    public V getCurrentValue()
	    throws IOException, InterruptedException {
	        return rr.getCurrentValue();
	    }  

	    @Override
	    public boolean nextKeyValue() throws IOException, InterruptedException {
	        return rr.nextKeyValue();
	    }
	}  

	public int run(String[] args) throws Exception {
		Configuration conf = new Configuration();

		Job job = new Job(conf);
		job.setJobName("TestCombine");
		job.setJarByClass(TestCombine.class);

		job.setMapperClass(ProvinceMapper.class);
		job.setReducerClass(ProvinceReducer.class);

		job.setInputFormatClass(CombineSequenceFileInputFormat.class);

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

		String inpath = "/home/hadoop/tmp/combine";
		String outpath = "/home/hadoop/tmp/combineout";
		Path p = new Path(outpath);

		FileSystem fs = FileSystem.get(conf);
		if (fs.exists(p)){
			fs.delete(p);
		}
		FileInputFormat.addInputPaths(job, inpath);
		FileOutputFormat.setOutputPath(job, p);

		return job.waitForCompletion(true) ? 0 : 1;
	} 

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