簡介

可以自定義輸出的格式和檔案，例如包含某欄位的輸出到一個指定檔案，不包含某欄位的輸出到另一個檔案。

案例

資料

www.nevesettle.com
www.baidu.com
www.qq.com
www.mi.com
www.jd.com
www.std.com

Mapper

package com.neve.outputformat;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

public class LogMapper extends Mapper<LongWritable, Text,Text, NullWritable> {

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

        context.write(value,NullWritable.get());
    }
}

 

Reducer

package com.neve.outputformat;

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

import java.io.IOException;

public class LogReducer extends Reducer<Text, NullWritable,Text,NullWritable> {

    @Override
    protected void reduce(Text key, Iterable<NullWritable> values, Context context) throws IOException, InterruptedException {

        for (NullWritable value : values) {
            context.write(key,value);
        }

    }
}

 

Driver

package com.neve.outputformat;

import com.neve.phone.FlowBean;
import com.neve.phone.FlowMapper;
import com.neve.phone.FlowReducer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
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.output.FileOutputFormat;

import java.io.IOException;

public class LogDriver {

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

        //1.建立配置
        Configuration configuration = new Configuration();
        //2.建立job
        Job job = Job.getInstance(configuration);
        //3.關聯驅動類
        job.setJarByClass(LogDriver.class);
        //4.關聯mapper和reducer類
        job.setMapperClass(LogMapper.class);
        job.setReducerClass(LogReducer.class);
        //5.設定mapper的輸出值和value
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(NullWritable.class);
        //6.設定最終的輸出值和value
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(NullWritable.class);
        //7.設定輸入輸出路徑
        FileInputFormat.setInputPaths(job,new Path("F:\\Workplace\\IDEA_Workplace\\hadoopStudy2\\outputformatinput"));
        FileOutputFormat.setOutputPath(job,new Path("F:\\Workplace\\IDEA_Workplace\\hadoopStudy2\\outputformatoutput"));
        //設定自定義的format類
        job.setOutputFormatClass(LogOutputFormat.class);
        //8.提交job
        job.waitForCompletion(true);

    }
}

 

LogOutputFormat

package com.neve.outputformat;

import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

public class LogOutputFormat extends FileOutputFormat<Text, NullWritable> {

    public RecordWriter<Text, NullWritable> getRecordWriter(TaskAttemptContext job) throws IOException, InterruptedException {
        LogRecordWriter logw = new LogRecordWriter(job);
        return logw;
    }
}
	

LogRecordWriter

package com.neve.outputformat;

import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

import java.io.IOException;

public class LogRecordWriter extends RecordWriter<Text, NullWritable> {

    //定義輸出路徑
    private String nelog = "F:\\nelog.log";
    private String otherlog = "F:\\otherlog.log";

    private FileSystem fs ;
    private FSDataOutputStream neos;
    private FSDataOutputStream otheros;


    public LogRecordWriter(TaskAttemptContext job) throws IOException {
        //獲取檔案系統物件
        fs = FileSystem.get(job.getConfiguration());
        neos = fs.create(new Path(nelog));
        otheros = fs.create(new Path(otherlog));
    }

    public void write(Text key, NullWritable value) throws IOException, InterruptedException {
        String string = key.toString();
        if (string.contains("neve")){
            neos.writeBytes(string + "\r");
        }else {
            otheros.writeBytes(string + "\r");
        }
    }

    public void close(TaskAttemptContext context) throws IOException, InterruptedException {
        IOUtils.closeStream(neos);
        IOUtils.closeStream(otheros);
    }
}