mapreduce输出乱码的处理

mapreduce输出乱码的处理，主要在于数据的编码，默认是以utf-8编码。

若数据源不是以utf-8编码，如以gbk编码的。若在mapreduce中要以gbk进行解码。

核心语句：

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String str = new String(value.getBytes(), 0, value.getLength(), "GBK");

解释：value.getBytes()是获取字节码数据，转换成字符码是需要加相应编码。

程序实验：

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package org.two;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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 java.io.IOException;

public class CleanOneDriver {
    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
        Configuration conn = new Configuration();

        Job job = Job.getInstance(conn);

        job.setJarByClass(CleanOneDriver.class);
        job.setMapperClass(CleanOneMapper.class);
        job.setReducerClass(CleanOneReduce.class);

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

        FileInputFormat.addInputPath(job,new Path(args[0]));
        FileOutputFormat.setOutputPath(job,new Path(args[1]));

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



    }

    private static class CleanOneMapper extends Mapper<LongWritable,Text,Text,NullWritable> {
        @Override
        protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, NullWritable>.Context context) throws IOException, InterruptedException {
            String str = new String(value.getBytes(), 0, value.getLength(), "GBK");
            context.write(new Text(str),NullWritable.get());
        }
    }

    private static class CleanOneReduce extends Reducer<Text,NullWritable,Text,NullWritable> {
        @Override
        protected void reduce(Text key, Iterable<NullWritable> values, Reducer<Text, NullWritable, Text, NullWritable>.Context context) throws IOException, InterruptedException {
            context.write(key,NullWritable.get());
        }
    }
}