hadoop_wordcount_1023

package s26;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;
import java.util.StringTokenizer;

public class MyMap extends Mapper<LongWritable,Text,Text,IntWritable> {

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        //super.map(key, value, context);

        StringTokenizer st = new StringTokenizer(value.toString());
        Text result = new Text();
        IntWritable one = new IntWritable(1);

        while (st.hasMoreTokens()){
            String word = st.nextToken();
            result.set(word);
            context.write(result,one);
        }
    }
}

package s26;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

public class MyRed extends Reducer<Text,IntWritable,Text,IntWritable> {

    @Override
    protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        //super.reduce(key, values, context);
        int sum = 0;
        for(IntWritable i:values){
            sum += i.get();
        }
        context.write(key,new IntWritable(sum));

    }
}






-----------

package s26;

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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

import java.io.IOException;

public class MyJob {

    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

        /*指定InputPath、outputPath*/
        args=new String[]{"hdfs://master:9000/root/experiment/datas","hdfs://master:9000/root/experiment/output"};
        if(args.length!=2){
            System.err.println("Usage:please put <in> <out>");
            System.exit(2);
        }
        /*创建Configuration对象*/
        Configuration conf = new Configuration();
        /*设置fs.defaultFS属性值*/
        conf.set("fs.defaultFS", "hdfs://master:9000");
        /*创建Job对象并进行初始化*/
        Job job = Job.getInstance(conf);
        /*指定Jar的来源类*/
        job.setJarByClass(MyJob.class);
        /*指定作业名称*/
        job.setJobName("MyJob");
        /*设置作业输出数据的键类*/
        job.setOutputKeyClass(Text.class);
        /*设置作业输出的值类*/
        job.setOutputValueClass(IntWritable.class);
        /*设置作业的Mapper类*/
        job.setMapperClass(MyMap.class);
        /*设置作业的Reducer类*/
        job.setReducerClass(MyRed.class);
        /*设置作业的输入格式类*/
        job.setInputFormatClass(TextInputFormat.class);
        /*设置作业的输出格式类*/
        job.setOutputFormatClass(TextOutputFormat.class);
        /*设置输出地址*/
        Path output=new Path(args[1]);
        /*获得文件系统*/
        FileSystem fs=FileSystem.get(conf);
        /*路径存在则删除该路径（文件夹）*/
        if(fs.exists(output)){
            fs.delete(output, true);
        }
        /*指定InputPath、outputPath*/
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        /*将作业提交给集群并等待它完成*/
        job.waitForCompletion(true);
    }
}