自定义数据类型，实现数据排序

package sort;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.net.URI;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
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;
import org.apache.hadoop.mapreduce.lib.partition.HashPartitioner;

public class SortApp {

static String INPUT_PATH = "hdfs://hadoop:9000/input";
static String OUT_PATH = "hdfs://hadoop:9000/out";
public static void main(String[] args) throws Exception {
Configuration configuration = new Configuration();
FileSystem fileSystem = FileSystem.get(new URI(INPUT_PATH), configuration);
if(fileSystem.exists(new Path(OUT_PATH))){
fileSystem.delete(new Path(OUT_PATH),true);
}
Job job = new Job(configuration, SortApp.class.getSimpleName());

//1.1 指定输入文件路径
FileInputFormat.setInputPaths(job, INPUT_PATH);
//指定哪个类用来格式化输入文件
job.setInputFormatClass(TextInputFormat.class);

//1.2指定自定义的Mapper类
job.setMapperClass(MyMapper.class);
//指定输出<k2,v2>的类型
job.setMapOutputKeyClass(NewK2.class);
job.setMapOutputValueClass(LongWritable.class);

//1.3 指定分区类
job.setPartitionerClass(HashPartitioner.class);
job.setNumReduceTasks(1);

//1.4 TODO 排序、分区

//1.5  TODO （可选）合并

//2.2 指定自定义的reduce类
job.setReducerClass(MyReducer.class);
//指定输出<k3,v3>的类型
job.setOutputKeyClass(LongWritable.class);
job.setOutputValueClass(LongWritable.class);

//2.3 指定输出到哪里
FileOutputFormat.setOutputPath(job, new Path(OUT_PATH));
//设定输出文件的格式化类
job.setOutputFormatClass(TextOutputFormat.class);

//把代码提交给JobTracker执行
job.waitForCompletion(true);
}

static class MyMapper extends Mapper<LongWritable, Text, NewK2,LongWritable>{
@Override
protected void map(LongWritable key, Text value,
org.apache.hadoop.mapreduce.Mapper<LongWritable, Text, NewK2,LongWritable>.Context context)
throws IOException, InterruptedException {
// TODO Auto-generated method stub
String[] splited = value.toString().split("\t");
NewK2 k2 = new NewK2(Long.parseLong(splited[0]), Long.parseLong(splited[1]));
LongWritable v2 = new LongWritable(Long.parseLong(splited[1]));
context.write(k2, v2);
}
}

static class MyReducer extends Reducer<NewK2, LongWritable, LongWritable, LongWritable>{
@Override
protected void reduce(NewK2 k2, Iterable<LongWritable> v2s,
org.apache.hadoop.mapreduce.Reducer<NewK2, LongWritable, LongWritable, LongWritable>.Context context)
throws IOException, InterruptedException {
// TODO Auto-generated method stub
context.write(new LongWritable(k2.first), new LongWritable(k2.second));
}
}

/**
* 问：为什么实现该类？
* 答：因为原来的v2不能参与排序，把原来的k2和v2封装到一个类中，作为新的k2
*
*/
static class NewK2 implements WritableComparable<NewK2>{

Long first;
Long second;

public NewK2(){}

public NewK2(long first, long second){
this.first = first;
this.second = second;
}

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

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

/**
* 当k2进行排序时，会调用该方法.
* 当第一列不同时，升序；当第一列相同时，第二列升序
*/
@Override
public int compareTo(NewK2 o) {
// TODO Auto-generated method stub
//long temp = this.first - o.first;
long temp = o.first - this.first;
if(temp !=0 )
return (int)temp;
else
return (int)(this.second - o.second);
}

@Override
public int hashCode() {
// TODO Auto-generated method stub
return this.first.hashCode()+this.second.hashCode();
}

@Override
public boolean equals(Object obj) {
// TODO Auto-generated method stub
if(!(obj instanceof NewK2)){
return false;
}
NewK2 oK2 = (NewK2)obj;
return (this.first==oK2.first)&&(this.second==oK2.second);
}

}

}