Hadoop MapReduce 二次排序

package SecondarySort;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Set;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.hadoop.mapreduce.Reducer;
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;

public class SecondarySort {

public static class IntPair implements WritableComparable<IntPair> {
int first, second;

public void set(int left, int right) {
first = left;
second = right;
}

public int getFirst() {
return first;
}

public int getSecond() {
return second;
}

@Override
public void readFields(DataInput arg0) throws IOException {
// TODO Auto-generated method stub
first = arg0.readInt();
second = arg0.readInt();
}

@Override
public void write(DataOutput arg0) throws IOException {
// TODO Auto-generated method stub
arg0.writeInt(first);
arg0.writeInt(second);
}

// 关键：自定义类型的比较方法
@Override
public int compareTo(IntPair arg0) {
// TODO Auto-generated method stub
if (first != arg0.first) {
return first < arg0.first ? -1 : 1;
} else if (second != arg0.second) {
return second < arg0.second ? -1 : 1;
} else {
return 0;
}
}

public int hashCode() {
return first * 157 + second;
}

public boolean equals(Object right) {
if (right == null)
return false;
if (this == right)
return true;
if (right instanceof IntPair) {
IntPair r = (IntPair) right;
return r.first == first && r.second == second;
} else {
return false;
}
}
}

public static class FirstPartitioner extends
Partitioner<IntPair, IntWritable> { // 类型要和Mapper输出的一样

@Override
public int getPartition(IntPair arg0, IntWritable arg1, int arg2) {
// TODO Auto-generated method stub
return Math.abs((arg0.getFirst() * 127) % arg2);
}

}

/*
* 第一种方法，实现接口RawComparator 数据类型的比较在MapReduce中式及其重要的,
* Mapreduce中有一个排序阶段，key和其他的key相比较。 针对此，Hadoop 提供的一个优化是 RawComparator
*
* public static class GroupingComparator implements RawComparator<IntPair>{
*
* @Override public int compare(IntPair arg0, IntPair arg1) { // TODO
* Auto-generated method stub int l = arg0.getFirst(); int r =
* arg0.getFirst(); return l == r ? 0 : (l < r ? -1 : 1); }
*
* @Override public int compare(byte[] b1, int s1, int l1, byte[] b2, int
* s2, int l2) { return WritableComparator.compareBytes(b1, s1,
* Integer.SIZE/8, b2, s2, Integer.SIZE/8); } }
*/

// 方法二
public static class GroupingComparator extends WritableComparator {
protected GroupingComparator() {
super(IntPair.class, true);// 调用父类的构造函数
}

public int compare(WritableComparable w1, WritableComparable w2) {
IntPair i1 = (IntPair) w1;
IntPair i2 = (IntPair) w2;
int l = i1.getFirst();
int r = i2.getFirst();
return l == r ? 0 : (l < r ? -1 : 1);
}
}

public static class Map extends
Mapper<LongWritable, Text, IntPair, IntWritable> {
private final IntPair ip = new IntPair();
private final IntWritable iw = new IntWritable();

public void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String line = value.toString();
StringTokenizer st = new StringTokenizer(line);
int left = 0;
int right = 0;
if (st.hasMoreTokens()) {
left = Integer.parseInt(st.nextToken());
if (st.hasMoreTokens()) {
right = Integer.parseInt(st.nextToken());
}
ip.set(left, right);
iw.set(right);
context.write(ip, iw);
}
}
}

public static class Reduce extends
Reducer<IntPair, IntWritable, Text, IntWritable> {
private final Text left = new Text();
private static final Text SEPARATOR = new Text(
"======================================");

public void reduce(IntPair key, Iterable<IntWritable> values,
Context context) throws IOException, InterruptedException {
context.write(SEPARATOR, null);
left.set(Integer.toString(key.getFirst()));
for (IntWritable val : values) {
context.write(left, val);
}
}
}

public static void main(String[] args) throws IllegalArgumentException,
IOException, ClassNotFoundException, InterruptedException {
// TODO Auto-generated method stub
Configuration conf = new Configuration();
@SuppressWarnings("deprecation")
Job job = new Job(conf, "mysecondarysort");
job.setJarByClass(SecondarySort.class);
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);
job.setPartitionerClass(FirstPartitioner.class);

job.setGroupingComparatorClass(GroupingComparator.class);

job.setMapOutputKeyClass(IntPair.class);
job.setMapOutputValueClass(IntWritable.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);
FileInputFormat.setInputPaths(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}

}