1. OutputFormat 接口实现类

OutputFormat是MapReduce输出的基类，所有实现MapReduce输出都实现了OutputFormat 接口。下面我们介绍几种常见的OutputFormat实现类

OutputFormat实现类
默认输出格式TextOutputFormat
自定义OutputFormat

应用场景：

例如：输出数据到MySQL/HBase/Elasticsearch等存储框架中

自定义OutputFormat步骤

自定义一个类继承FileOutputFormat
改写RecordWriter，具体改写输出数据的方法write()

2. 自定义OutputFormat 案例实操

需求过滤输入的log 日志，包含atguigu 的网站输出到e:/atguigu.log，不包含atguigu 的网站输出到e:/other.log

需求分析

需求：过滤输入的log日志，包含atguigu的网站输出到e:/atguigu.log，不包含atguigu的网站输出到e:/other.log

输入数据

http://www.baidu.com
http://www.google.com
http://cn.bing.com
http://www.atguigu.com
http://www.sohu.com
http://www.sina.com
http://www.sin2a.com
http://www.sin2desa.com
http://www.sindsafa.com

输出数据

http://www.atguigu.com
    http://cn.bing.com
    http://www.baidu.com
    http://www.google.com
    http://www.sin2a.com
    http://www.sin2desa.com
    http://www.sina.com
    http://www.sindsafa.com
    http://www.sohu.com

自定义一个OutputFormat类
- 创建一个类LogRecordWriter继承RecordWriter
- 创建两个文件的输出流：atguiguOut、otherOut
- 如果输入数据包含atguigu，输出到atguiguOut流如果不包含atguigu，输出到otherOut流

案例实操

编写LogMapper 类

package com.atguigu.mapreduce.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 {
        //不做任何处理,直接写出一行log 数据
        context.write(value,NullWritable.get());
    }
}

编写 LogReducer类

package com.atguigu.mapreduce.outputformat;
import org.apache.hadoop.io.Nu llWritable;
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, Itera ble<NullWritable> values, Context context) throws IOException, InterruptedException {
    防止有相同的数据 迭代写出
        for (NullWritable value : values) {
            context.write(key,NullWritable.get());
        }
    }
}

自定义一个 LogOutputFormat类

package com.atguigu.mapreduce.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.
import java.io.IOException;
public class LogOutputFormat extends FileOutputFormat<Text, NullWritable>
    @Override
    public RecordWriter<Text, NullWritable>getRecordWriter(TaskAttemptContext job) throw s IOException,InterruptedException {
        //创建一个自定义的 RecordWriter 返回
        LogRecordWriter logRecordWriter = new LogRecordWriter(job);
        return logRecordWriter;
    }
}

编写 LogRecordWriter类

package com.atguigu.mapreduce.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> {

    private FSDataOutputStream atguiguOut;
    private FSDataOutputStream otherOut;

    public LogRecordWriter(TaskAttemptContext job) {

        try {

            //获取文件系统对象
            FileSystem fs = FileSystem.get(job.getConfiguration());

            //用文件系统对象创建两个输出流对应不同的目录
            atguiguOut = fs.create(new Path("d:/hadoop/atguigu.log"));
            otherOut = fs.create(new Path("d:/hadoop/other.log"));

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    @Override
    public void write(Text key, NullWritable value) throws IOException, InterruptedException {

        String log = key.toString();

        //根据一行的log数据是否包含atguigu,判断两条输出流输出的内容
        if (log.contains("atguigu")) {

            atguiguOut.writeBytes(log + "\n");

        } else {

            otherOut.writeBytes(log + "\n");

        }

    }

    @Override
    public void close(TaskAttemptContext context) throws IOException, InterruptedException {

        //关流
        IOUtils.closeStream(atguiguOut);

        IOUtils.closeStream(otherOut);

    }

}

编写LogDriver类

package com.atguigu.mapreduce.outputformat;

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 {

        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf);

        job.setJarByClass(LogDriver.class);
        job.setMapperClass(LogMapper.class);
        job.setReducerClass(LogReducer.class);

        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(NullWritable.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(NullWritable.class);
 
        //设置自定义的outputformat
        job.setOutputFormatClass(LogOutputFormat.class);

        FileInputFormat.setInputPaths(job, new Path("D:\\input"));
        //虽然我们自定义了outputformat，但是因为我们的outputformat继承自fileoutputformat
        //而fileoutputformat要输出一个_SUCCESS文件，所以在这还得指定一个输出目录
        FileOutputFormat.setOutputPath(job, new Path("D:\\logoutput"));
 
        boolean b = job.waitForCompletion(true);
        System.exit(b ? 0 : 1);

    }

}

OutputFormat数据输出

1. OutputFormat 接口实现类

2. 自定义OutputFormat 案例实操