MR 文件合并

 package com.euphe.filter;

 import com.euphe.util.HUtils;
 import com.euphe.util.Utils;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.conf.Configured;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 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;
 import org.apache.hadoop.util.Tool;

 import java.io.IOException;

 public class ReductionJob extends Configured implements Tool {
     public static class Map extends Mapper<Object, Text, Text, Text> {
         private static Text text = new Text();

         public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
             text = value;
             context.write(text, new Text());
         }
     }

     public static class Reduce extends Reducer<Text, Text, Text, Text> {
         public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
             context.write(key, new Text());
         }
     }
     @Override
     public int run(String[] args) throws Exception {
         Configuration conf = HUtils.getConf();
         conf.set("mapreduce.job.jar", Utils.getRootPathBasedPath("WEB-INF/jars/redu.jar"));
         String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();//解析命令行参数
         if (otherArgs.length !=2) {//要求必须有输入和输出路径两个参数
             System.err.println("Usage: com.euphe.filter.ReductionJob <in> <out>");
             System.exit(2);
         }
         Job job =  Job.getInstance(conf,"Reduction input  :"+otherArgs[0]+" to "+otherArgs[1]);
         job.setJarByClass(ReductionJob.class);
         job.setMapperClass(Map.class);
         job.setReducerClass(Reduce.class);
         job.setNumReduceTasks(1);

         job.setOutputKeyClass(Text.class);
         job.setOutputValueClass(Text.class);

         FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
         FileOutputFormat.setOutputPath(job,new Path(otherArgs[1]));
         FileSystem.get(conf).delete(new Path(otherArgs[1]), true);//调用任务前先删除输出目录
         return job.waitForCompletion(true) ? 0 : 1;
     }
 }