使用eclipse的快捷键自动生成的map或者reduce函数的参数中：“org.apache.hadoop.mapreduce.Reducer.Context context”

2021-12-12 11:54:17

今天在测试mapreduce的程序时，就是简单的去重，对照课本上的程序和自己的程序，唯一不同的就是“org.apache.hadoop.mapreduce.Reducer.Context context”，我写的程序如下：

package com.pro.bq;

import java.io.IOException;

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.Mapper;

import org.apache.hadoop.mapreduce.Reducer;

import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import org.apache.hadoop.util.GenericOptionsParser;

public class Dedup {

    public static class Map extends Mapper<Object,Text, Text, Text>{

        private Text line=new Text();

    @Override

    protected void map(Object key, Text value,

            Context context)

            throws IOException, InterruptedException {

        // TODO Auto-generated method stub

          line=value;

          context.write(line, new Text(""));

    }

    }

    public static class Reduce extends Reducer<Text, Text, Text, Text>

    {

        @SuppressWarnings("unchecked")

        protected void reduce(Text key, Iterable<Text> value,
org.apache.hadoop.mapreduce.Reducer.Context context)

                throws IOException, InterruptedException {

            // TODO Auto-generated method stub

            context.write(key, new Text(""));

        }

    }

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

        Configuration conf=new Configuration();

//        conf.set("mapred.job.tracker", "localhost:9001");

        String hdfs=new String("hdfs://localhost:9000/user/haduser/");

        String[] ioStr=new String[]{hdfs+"input",hdfs+"output/outDedup"};

        //自己在代码中定义路径，否则的话就要就要在程序的输入参数中设置了

        String[] otherStr=new GenericOptionsParser(conf, ioStr).getRemainingArgs();

        if(otherStr.length!=2)

        {

            System.err.println("Usage: Data deduplication <in> <out>");

            System.exit(2);

        }

        Job job=new Job(conf, "Data deduplication");

        job.setJarByClass(Dedup.class);

        job.setMapperClass(Map.class);

        job.setCombinerClass(Reduce.class);

        job.setReducerClass(Reduce.class);

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(Text.class);

        FileInputFormat.addInputPath(job, new Path(otherStr[0]));

        FileOutputFormat.setOutputPath(job, new Path(otherStr[1]));

        System.exit(job.waitForCompletion(true) ? 0:1);

    }

}

课本上给出的程序如下：

package com.pro.bq;

import java.io.IOException;

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.Mapper;

import org.apache.hadoop.mapreduce.Reducer;

import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import org.apache.hadoop.util.GenericOptionsParser;

public class Dedup {

    public static class Map extends Mapper<Object,Text, Text, Text>{

        private Text line=new Text();

    protected void map(Object key, Text value,

            Context context)

            throws IOException, InterruptedException {

        // TODO Auto-generated method stub

          line=value;

          context.write(line, new Text(""));

    }

    }

    public static class Reduce extends Reducer<Text, Text, Text, Text>

    {

        protected void reduce(Text key, Iterable<Text> value,

                Context context)

                throws IOException, InterruptedException {

            // TODO Auto-generated method stub

            context.write(key, new Text(""));

        }

    }

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

        Configuration conf=new Configuration();

//        conf.set("mapred.job.tracker", "localhost:9001");

        String hdfs=new String("hdfs://localhost:9000/user/haduser/");

        String[] ioStr=new String[]{hdfs+"input",hdfs+"output/outDedup"};

        //自己在代码中定义路径，否则的话就要就要在程序的输入参数中设置了

        String[] otherStr=new GenericOptionsParser(conf, ioStr).getRemainingArgs();

        if(otherStr.length!=2)

        {

            System.err.println("Usage: Data deduplication <in> <out>");

            System.exit(2);

        }

        Job job=new Job(conf, "Data deduplication");

        job.setJarByClass(Dedup.class);

        job.setMapperClass(Map.class);

        job.setCombinerClass(Reduce.class);

        job.setReducerClass(Reduce.class);

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(Text.class);

        FileInputFormat.addInputPath(job, new Path(otherStr[0]));

        FileOutputFormat.setOutputPath(job, new Path(otherStr[1]));

        System.exit(job.waitForCompletion(true) ? 0:1);

    }

}

测试的文件file1.txt是：

2012-3-1 a

2012-3-2 b

2012-3-3 c

2012-3-4 d

2012-3-5 a

2012-3-6 b

2012-3-7 c

2012-3-3 c

file2.txt:

2012-3-1 b

2012-3-2 a

2012-3-3 b

2012-3-4 d

2012-3-5 a

2012-3-6 c

2012-3-7 d

2012-3-3 c

按照我写的运行的结果是：

2012-3-1 a

2012-3-1 b

2012-3-2 a

2012-3-2 b

2012-3-3 b

2012-3-3 c

2012-3-3 c

2012-3-3 c

2012-3-4 d

2012-3-4 d

2012-3-5 a

2012-3-5 a

2012-3-6 b

2012-3-6 c

2012-3-7 c

2012-3-7 d

想要的结果是:

2012-3-1 a

2012-3-1 b

2012-3-2 a

2012-3-2 b

2012-3-3 b

2012-3-3 c

2012-3-4 d

2012-3-5 a

2012-3-6 b

2012-3-6 c

2012-3-7 c

2012-3-7 d

不知道为什么？暂且记下，有懂的希望不吝赐教，我是菜鸟...

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