hadoop 实现多文件输出

需求

不同的key输出到不同的文件

txt文件

multiple.txt

中国;22
美国;4342
中国;123
日本;44
日本;6
美国;55
美国;43765
日本;786
日本;55

Java

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
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.mapreduce.lib.output.MultipleOutputs;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

import java.io.IOException;


public class MultipleApp {
    /**
     * map任务
     *
     * **/
    public static class PMapper extends Mapper<LongWritable, Text, Text, Text>{
        @Override
        protected void map(LongWritable key, Text value,Context context)
                throws IOException, InterruptedException {
            String ss[]=value.toString().split(";");
            context.write(new Text(ss[0]), new Text(ss[1]));
        }
    }


    public static class PReduce extends Reducer<Text, Text, Text, Text>{
        /**
         * 设置多个文件输出
         * */
        private MultipleOutputs mos;
        @Override
        protected void setup(Context context) throws IOException, InterruptedException {
            mos = new MultipleOutputs(context);//初始化mos
        }
        @Override
        protected void reduce(Text arg0, Iterable<Text> arg1, Context arg2) throws IOException, InterruptedException {

            String key=arg0.toString();
            for(Text t:arg1){
                if(key.equals("中国")){
                    mos.write("china", arg0,t);
                } else if(key.equals("美国")){
                    mos.write("USA", arg0,t);
                } else if(key.equals("日本")){
                    mos.write("japan", arg0,t);
                }
            }
        }

        @Override
        protected void cleanup(
                Context context)
                throws IOException, InterruptedException {
            mos.close();//释放资源
        }
    }


    public static void main(String[] args) throws Exception{
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "file:///");
        Job job = Job.getInstance(conf);

        /**Job任务**/
        job.setJobName("multiple");
        job.setJarByClass(MultipleApp.class);
        job.setMapperClass(PMapper.class);
        job.setReducerClass(PReduce.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        /**
         * 注意在初始化时需要设置输出文件的名
         * 另外名称，不支持中文名，仅支持英文字符
         *
         * **/
        MultipleOutputs.addNamedOutput(job, "china", TextOutputFormat.class, Text.class, Text.class);
        MultipleOutputs.addNamedOutput(job, "USA", TextOutputFormat.class, Text.class, Text.class);
        MultipleOutputs.addNamedOutput(job, "japan", TextOutputFormat.class, Text.class, Text.class);

        //添加输入路径
        FileInputFormat.addInputPath(job,new Path("C://multiple.txt"));
        //设置输出路径
        FileOutputFormat.setOutputPath(job,new Path("C://out"));

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

结果

part-r-00000为框架自动生成的空文件，可忽略