MapReduce_dedup

package MapReduce;

import java.io.IOException;
import java.net.URI;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
//import org.apache.hadoop.io.IntWritable;
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;
 
public class Dedup {
    private static final String INPUT_PATH = "hdfs://h201:9000/user/hadoop/input";
    private static final String OUTPUT_PATH = "hdfs://h201:9000/user/hadoop/output";
    //map将输入中的value复制到输出数据的key上，并直接输出
    public static class Map extends Mapper<Object,Text,Text,Text>{
        private static Text line=new Text();//每行数据     
        //实现map函数
        public void map(Object key,Text value,Context context) throws IOException,InterruptedException{
            line=value;
            context.write(line, new Text(""));
        }       
    }
    //reduce将输入中的key复制到输出数据的key上，并直接输出
    public static class Reduce extends Reducer<Text,Text,Text,Text>{
        //实现reduce函数
        public void reduce(Text key,Iterable<Text> values,Context context) throws IOException,InterruptedException{
            context.write(key, new Text(""));//行去重
        }       
    }
    public static void main(String[] args) throws Exception{
        Configuration conf = new Configuration();
        //这句话很关键
        conf.set("mapred.jar","Dedup.jar");
        final FileSystem fileSystem = FileSystem.get(new URI(OUTPUT_PATH), conf);//读路径信息
        fileSystem.delete(new Path(OUTPUT_PATH), true);//删除路径信息 输出路径不能存在
        //String[] ioArgs=new String[]{"dedup_in","dedup_out"};//dedup_in在/user/hadoop下ioArgs对应的是括号内的
        //String[] otherArgs = new GenericOptionsParser(conf, ioArgs).getRemainingArgs();//把ioArgs赋给oherArgs,引用Generic这个类，调用getRemain这个方法 conf代表的是初始化
        //if (otherArgs.length != 2) {
            //System.err.println("Usage: Data Deduplication <in> <out>");
            //System.exit(2);
            //}
        final Job job = new Job(conf, WordCountApp.class.getSimpleName());
        job.setJarByClass(Dedup.class); //启动job
        FileInputFormat.setInputPaths(job, INPUT_PATH);
        //设置Map、Combine和Reduce处理类
        job.setMapperClass(Map.class);
        job.setCombinerClass(Reduce.class);
        job.setReducerClass(Reduce.class);    
         //设置输出类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);    
         //设置输入和输出目录
        FileOutputFormat.setOutputPath(job, new Path(OUTPUT_PATH));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
        }
63 }

结果

[hadoop@h201 Dedup]$ hadoop fs -cat /user/hadoop/output/part-r-00000
18/03/18 22:02:59 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
ayi mama
ayi shushu
cai wen wei
didi mama
gege jiejie didi
hello baba
hello mama
hello word
jiejie hello
mama baba jiejie gege
mama jiejie
meimei jiejie

原始数据

[hadoop@h201 Dedup]$ hadoop fs -cat /user/hadoop/input/counttext1.txt
18/03/18 22:07:08 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
hello baba
hello mama
mama jiejie
jiejie hello
[hadoop@h201 Dedup]$ hadoop fs -cat /user/hadoop/input/counttext.txt
18/03/18 22:07:18 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
hello mama
hello baba
hello word
cai wen wei
mama baba jiejie gege
gege jiejie didi
meimei jiejie
didi mama
ayi shushu
ayi mama
hello mama
hello baba
hello word
cai wen wei
mama baba jiejie gege
gege jiejie didi
meimei jiejie
didi mama
ayi shushu
ayi mama
hello mama
hello baba
hello word
cai wen wei
mama baba jiejie gege
gege jiejie didi
meimei jiejie
didi mama
ayi shushu
ayi mama
hello mama
hello baba
hello word
cai wen wei
mama baba jiejie gege
gege jiejie didi
meimei jiejie
didi mama
ayi shushu
ayi mama
hello mama
hello baba
hello word
cai wen wei
mama baba jiejie gege
gege jiejie didi
meimei jiejie
didi mama
ayi shushu
ayi mama