期间遇到了无法转value的值为int型，我采用try catch解决

str2 2
str1 1
str3 3
str1 4
str4 7
str2 5
str3 9

用的\t隔开，得到结果 

str1 1,4 

str2 2,5

str3 3,9

str4 7

我这里map，reduce都是单独出来的类，用了自定义的key

package com.kane.mr;

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


import org.apache.hadoop.io.WritableComparable;


import com.j_spaces.obf.fi;
//str2 2
//str1 1
//str3 3
//str1 4
//str4 7
//str2 5
//str3 9
public class IntPair implements WritableComparable<IntPair>{
public String getFirstKey() {
return firstKey;
}


public void setFirstKey(String firstKey) {
this.firstKey = firstKey;
}


public int getSecondKey() {
return secondKey;
}


public void setSecondKey(int secondKey) {
this.secondKey = secondKey;
}


private String firstKey;//str1
private int secondKey;//1
@Override
public void write(DataOutput out) throws IOException {
out.writeUTF(firstKey);
out.writeInt(secondKey);

}


@Override
public void readFields(DataInput in) throws IOException {
firstKey=in.readUTF();
secondKey=in.readInt();

}
//这里做比较，另一个是自身本类,对key进行排序
@Override
public int compareTo(IntPair o) {
// int first=o.getFirstKey().compareTo(this.firstKey);
// if (first!=0) {
// return first;
// }
// else {
// return o.getSecondKey()-this.secondKey;
// }
return o.getFirstKey().compareTo(this.getFirstKey());

}


}

package com.kane.mr;


import java.io.IOException;


import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class SortMapper extends Mapper<Object,Text,IntPair,IntWritable>{
public IntPair intPair=new IntPair();
public IntWritable intWritable=new IntWritable(0);
@Override
protected void map(Object key, Text value,//str1 1
Context context)
throws IOException, InterruptedException {
//String[] values=value.toString().split("/t");
System.out.println(value);
int intValue;
try {
intValue = http://www.mamicode.com/Integer.parseInt(value.toString());
} catch (NumberFormatException e) {
intValue=http://www.mamicode.com/6;
}//不加try catch总是读取value时，无法转成int型
intPair.setFirstKey(key.toString());
intPair.setSecondKey(intValue);
intWritable.set(intValue);
context.write(intPair, intWritable);// key(str2 2) 2
}

}

package com.kane.mr;


import java.io.IOException;
import java.util.Iterator;


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


public class SortReducer extends Reducer<IntPair, IntWritable, Text,Text>{


@Override
protected void reduce(IntPair key, Iterable<IntWritable> values,
Context context)
throws IOException, InterruptedException {
StringBuffer combineValue=http://www.mamicode.com/new StringBuffer();
Iterator<IntWritable> itr=values.iterator();
while (itr.hasNext()) {
int value=http://www.mamicode.com/itr.next().get();
combineValue.append(value+",");
}
context.write(new Text(key.getFirstKey()),new Text(combineValue.toString()));
}



}

package com.kane.mr;


import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapreduce.Partitioner;

public class PartionTest extends Partitioner<IntPair, IntWritable>{

@Override
public int getPartition(IntPair key, IntWritable value, int numPartitions) {//reduce个数

return (key.getFirstKey().hashCode()&Integer.MAX_VALUE%numPartitions);
}


}

package com.kane.mr;


import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;


public class TextComparator extends WritableComparator{
public TextComparator(){
super(IntPair.class,true);
}


@Override
public int compare(WritableComparable a, WritableComparable b) {
IntPair o1=(IntPair)a;
IntPair o2=(IntPair)b;
return o1.getFirstKey().compareTo(o2.getFirstKey());
}

}

package com.kane.mr;


import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
@SuppressWarnings("rawtypes")
public class TextIntCompartor extends WritableComparator{


protected TextIntCompartor() {
super(IntPair.class,true);
}


@Override
public int compare(WritableComparable a,  WritableComparable b) {
IntPair o1=(IntPair)a;
IntPair o2=(IntPair)b;
int first=o1.getFirstKey().compareTo(o2.getFirstKey());
if (first!=0) {
return first;
}
else {
return o1.getSecondKey()-o2.getSecondKey();
}
}



}

package com.kane.mr;


import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.KeyValueTextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;


public class SortMain {
public static void main(String[] args) throws Exception{
Configuration conf = new Configuration();
   String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
   if (otherArgs.length != 2) {
     System.err.println("Usage: wordcount <in> <out>");
     System.exit(2);
   }
   Job job = new Job(conf, "Sort");
   job.setJarByClass(SortMain.class);
   job.setInputFormatClass(KeyValueTextInputFormat.class);
   job.setMapperClass(SortMapper.class);
   //job.setCombinerClass(IntSumReducer.class);
   job.setReducerClass(SortReducer.class);
   
   job.setMapOutputKeyClass(IntPair.class);
   job.setMapOutputValueClass(IntWritable.class);
   
   job.setSortComparatorClass(TextIntCompartor.class);
   job.setGroupingComparatorClass(TextComparator.class);//以key 进行group by
   job.setPartitionerClass(PartionTest.class);
   
   job.setOutputKeyClass(Text.class);
   job.setOutputValueClass(Text.class);
   
   FileInputFormat.addInputPath(job, new Path(otherArgs[0]));//输入参数，对应hadoop jar 对应类运行时在后面加的第一个参数
   FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));//输出参数
   System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}

导出jar包放到hadoop下，然后讲sort.txt放入到hdfs中，然后用hadoop jar KaneTest/sort.jar com.kane.mr.SoetMain /kane/sort.txt /kane/output命令执行