ChainMapper和ChainReducer

The ChainMapper class allows to use multiple Mapper classes within a single Map task.

The ChainReducer class allows to chain multiple Mapper classes after a Reducer within the Reducer task.

http://www.oratea.net/?p=371

通过ChainMapper可以将多个map类合并成一个map任务。

下面个这个例子没什么实际意思，但是很好的演示了ChainMapper的作用。

源文件
100 tom 90
101 mary 85
102 kate 60

map00的结果，过滤掉100的记录
101 mary 85
102 kate 60

map01的结果，过滤掉101的记录
102 kate 60

reduce结果
102 kate 60

package org.myorg;

import java.io.IOException;
import java.util. * ;
import java.lang.String;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.conf. * ;
import org.apache.hadoop.io. * ;
import org.apache.hadoop.mapred. * ;
import org.apache.hadoop.util. * ;
import org.apache.hadoop.mapred.lib. * ;

public class WordCount
{

    public static class Map00 extends MapReduceBase implements Mapper
    {

        public void map(Text key, Text value, OutputCollector output, Reporter reporter) throws IOException
        {

            Text ft = new Text(“ 100 ″);

            if ( ! key.equals(ft))
            {
                output.collect(key, value);
            }
        }
    }

    public static class Map01 extends MapReduceBase implements Mapper
    {

        public void map(Text key, Text value, OutputCollector output, Reporter reporter) throws IOException
        {

            Text ft = new Text(“ 101 ″);

            if ( ! key.equals(ft))
            {
                output.collect(key, value);
            }
        }
    }

    public static class Reduce extends MapReduceBase implements Reducer
    {
        public void reduce(Text key, Iterator values, OutputCollector output, Reporter reporter) throws IOException
        {

            while (values.hasNext())
            {
                output.collect(key, values.next());
            }

        }
    }

    public static void main(String[] args) throws Exception
    {

        JobConf conf = new JobConf(WordCount. class );
        conf.setJobName(“wordcount00″);

        conf.setInputFormat(KeyValueTextInputFormat. class );
        conf.setOutputFormat(TextOutputFormat. class );

        ChainMapper cm = new ChainMapper();

        JobConf mapAConf = new JobConf( false );
        cm.addMapper(conf, Map00. class , Text. class , Text. class , Text. class , Text. class , true , mapAConf);

        JobConf mapBConf = new JobConf( false );
        cm.addMapper(conf, Map01. class , Text. class , Text. class , Text. class , Text. class , true , mapBConf);

        conf.setReducerClass(Reduce. class );

        conf00.setOutputKeyClass(Text. class );
        conf00.setOutputValueClass(Text. class );

        FileInputFormat.setInputPaths(conf, new Path(args[ 0 ]));
        FileOutputFormat.setOutputPath(conf, new Path(args[ 1 ]));

        JobClient.runJob(conf);

    }
}

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另外一个例子，代码很多，其实很简单，Conn几个类都是相同的

http://yixiaohuamax.iteye.com/blog/684244

package com.oncedq.code;

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

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.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.TextInputFormat;
import org.apache.hadoop.mapred.TextOutputFormat;
import org.apache.hadoop.mapred.jobcontrol.Job;
import org.apache.hadoop.mapred.jobcontrol.JobControl;
import org.apache.hadoop.mapred.lib.ChainMapper;

import com.oncedq.code.util.DateUtil;

public class ProcessSample {
    public static class ExtractMappper extends MapReduceBase implements
            Mapper < LongWritable, Text, LongWritable, Conn1 > {

        @Override
        public void map(LongWritable arg0, Text arg1,
                OutputCollector < LongWritable, Conn1 > arg2, Reporter arg3)
                throws IOException {
            String line = arg1.toString();
            String[] strs = line.split( " ; " );
            Conn1 conn1 = new Conn1();
            conn1.orderKey = Long.parseLong(strs[ 0 ]);
            conn1.customer = Long.parseLong(strs[ 1 ]);
            conn1.state = strs[ 2 ];
            conn1.price = Double.parseDouble(strs[ 3 ]);
            conn1.orderDate = DateUtil.getDateFromString(strs[ 4 ], " yyyy-MM-dd " );
            LongWritable lw = new LongWritable(conn1.orderKey);
            arg2.collect(lw, conn1);
        }

    }

    private static class Conn1 implements WritableComparable < Conn1 > {
        public long orderKey;
        public long customer;
        public String state;
        public double price;
        public java.util.Date orderDate;

        @Override
        public void readFields(DataInput in) throws IOException {
            orderKey = in.readLong();
            customer = in.readLong();
            state = Text.readString(in);
            price = in.readDouble();
            orderDate = DateUtil.getDateFromString(Text.readString(in),
                    " yyyy-MM-dd " );
        }

        @Override
        public void write(DataOutput out) throws IOException {
            out.writeLong(orderKey);
            out.writeLong(customer);
            Text.writeString(out, state);
            out.writeDouble(price);
            Text.writeString(out, DateUtil.getDateStr(orderDate, " yyyy-MM-dd " ));
        }

        @Override
        public int compareTo(Conn1 arg0) {
            // TODO Auto-generated method stub
            return 0 ;
        }

    }

    public static class Filter1Mapper extends MapReduceBase implements
            Mapper < LongWritable, Conn1, LongWritable, Conn2 > {

        @Override
        public void map(LongWritable inKey, Conn1 c2,
                OutputCollector < LongWritable, Conn2 > collector, Reporter report)
                throws IOException {
            if (c2.state.equals( " F " )) {
                Conn2 inValue = new Conn2();
                inValue.customer = c2.customer;
                inValue.orderDate = c2.orderDate;
                inValue.orderKey = c2.orderKey;
                inValue.price = c2.price;
                inValue.state = c2.state;
                collector.collect(inKey, inValue);
            }
        }

    }

    private static class Conn2 implements WritableComparable < Conn1 > {
        public long orderKey;
        public long customer;
        public String state;
        public double price;
        public java.util.Date orderDate;

        @Override
        public void readFields(DataInput in) throws IOException {
            orderKey = in.readLong();
            customer = in.readLong();
            state = Text.readString(in);
            price = in.readDouble();
            orderDate = DateUtil.getDateFromString(Text.readString(in),
                    " yyyy-MM-dd " );
        }

        @Override
        public void write(DataOutput out) throws IOException {
            out.writeLong(orderKey);
            out.writeLong(customer);
            Text.writeString(out, state);
            out.writeDouble(price);
            Text.writeString(out, DateUtil.getDateStr(orderDate, " yyyy-MM-dd " ));
        }

        @Override
        public int compareTo(Conn1 arg0) {
            // TODO Auto-generated method stub
            return 0 ;
        }

    }

    public static class RegexMapper extends MapReduceBase implements
            Mapper < LongWritable, Conn2, LongWritable, Conn3 > {

        @Override
        public void map(LongWritable inKey, Conn2 c3,
                OutputCollector < LongWritable, Conn3 > collector, Reporter report)
                throws IOException {
            c3.state = c3.state.replaceAll( " F " , " Find " );
            Conn3 c2 = new Conn3();
            c2.customer = c3.customer;
            c2.orderDate = c3.orderDate;
            c2.orderKey = c3.orderKey;
            c2.price = c3.price;
            c2.state = c3.state;
            collector.collect(inKey, c2);
        }
    }

    private static class Conn3 implements WritableComparable < Conn1 > {
        public long orderKey;
        public long customer;
        public String state;
        public double price;
        public java.util.Date orderDate;

        @Override
        public void readFields(DataInput in) throws IOException {
            orderKey = in.readLong();
            customer = in.readLong();
            state = Text.readString(in);
            price = in.readDouble();
            orderDate = DateUtil.getDateFromString(Text.readString(in),
                    " yyyy-MM-dd " );
        }

        @Override
        public void write(DataOutput out) throws IOException {
            out.writeLong(orderKey);
            out.writeLong(customer);
            Text.writeString(out, state);
            out.writeDouble(price);
            Text.writeString(out, DateUtil.getDateStr(orderDate, " yyyy-MM-dd " ));
        }

        @Override
        public int compareTo(Conn1 arg0) {
            // TODO Auto-generated method stub
            return 0 ;
        }

    }

    public static class LoadMapper extends MapReduceBase implements
            Mapper < LongWritable, Conn3, LongWritable, Conn3 > {

        @Override
        public void map(LongWritable arg0, Conn3 arg1,
                OutputCollector < LongWritable, Conn3 > arg2, Reporter arg3)
                throws IOException {
            arg2.collect(arg0, arg1);
        }

    }

    public static void main(String[] args) {
        JobConf job = new JobConf(ProcessSample. class );
        job.setJobName( " ProcessSample " );
        job.setNumReduceTasks( 0 );
        job.setInputFormat(TextInputFormat. class );
        job.setOutputFormat(TextOutputFormat. class );
        JobConf mapper1 = new JobConf();
        JobConf mapper2 = new JobConf();
        JobConf mapper3 = new JobConf();
        JobConf mapper4 = new JobConf();
        ChainMapper cm = new ChainMapper();
        cm.addMapper(job, ExtractMappper. class , LongWritable. class , Text. class ,
                LongWritable. class , Conn1. class , true , mapper1);
        cm.addMapper(job, Filter1Mapper. class , LongWritable. class , Conn1. class ,
                LongWritable. class , Conn2. class , true , mapper2);
        cm.addMapper(job, RegexMapper. class , LongWritable. class , Conn2. class ,
                LongWritable. class , Conn3. class , true , mapper3);
        cm.addMapper(job, LoadMapper. class , LongWritable. class , Conn3. class ,
                LongWritable. class , Conn3. class , true , mapper4);
        FileInputFormat.setInputPaths(job, new Path( " orderData " ));
        FileOutputFormat.setOutputPath(job, new Path( " orderDataOutput " ));
        Job job1;
        try {
            job1 = new Job(job);
            JobControl jc = new JobControl( " test " );
            jc.addJob(job1);
            jc.run();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

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}