mapreduce--单词分析

WCDriver

package com.atguigu.mr.wordcount;
 
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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
 
import java.io.IOException;
 
/*
    程序的入口
    1.创建job实例并允许
 */
public class WCDriver {
    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
//        创建job实例
        Configuration conf=new Configuration();
        Job job=Job.getInstance(conf);
 
//        给job赋值
//        关联本程序的jar 运行必须写
        job.setJarByClass(WCDriver.class);
//        设置mapper reduce类
        job.setMapperClass(WCMapper.class);
        job.setReducerClass(WCReducer.class);
//        设置mapper输出的key value的类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(LongWritable.class);
//        设置最终输出的key value类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);
 
/*
设置输出路径
windows:
FileInputFormat.setInputPaths(job,new Path("//"));
FileInputFormat.setOutputPaths(job,new Path("//"));
 */
        FileInputFormat.setInputPaths(job,new Path(args[0]));
        FileOutputFormat.setOutputPath(job,new Path(args[1]));
//        FileInputFormat.setInputPaths(job,new Path("F:\\input"));
//        FileOutputFormat.setOutputPath(job,new Path("F:\\aa\\output"));
//        运行job
        boolean b=job.waitForCompletion(true);
        System.out.println("b===="+ b);
 
 
 
    }
}

 WCMapper

package com.atguigu.mr.wordcount;
 
import org.apache.commons.net.imap.IMAP;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import org.xbill.DNS.LOCRecord;
 
import java.io.IOException;
 
/*
    mapper阶段会运行MapTask -会调用Mappper类
      在该类中实现业务逻辑
 */
public class WCMapper extends Mapper {
 
    private Text outKey=new Text();
    private LongWritable outValue=new LongWritable();
 
    /**
     *
     * @param key 读取数据时的偏移量
     * @param value 读取的数据
     * @param context 上下文
     * @throws IOException
     * @throws InterruptedException
     */
 
    @Override
    protected void map(LongWritable key, Text value, Mapper.Context context) throws IOException, InterruptedException {
//        super.map(key, value, context);
//        1.将数据进行切割
 
 
 
//        1.1将Text转换成string---为了使用String API
        String line=value.toString();
//        1.2对数据切割
        String[] words =line.split("");
 
//        2.遍历数据
        for (String word:words){
//            3.封装key，value
//            创建key，value对象
 
 
//            赋值
            outKey.set(word);
            outValue.set(1);
//            4.将 key，value写进去
            context.write(outKey,outValue);
 
 
        }
//
//
 
    }
}

 WCReduce

package com.atguigu.mr.wordcount;
 
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
 
import java.io.IOException;
 
/*
    reduce阶段会运行reduceTask -会调用reducer类
      在该类中实现业务逻辑
 */
public class WCReducer extends Reducer  {
    private LongWritable outValue=new LongWritable();
    /**
     *
     * @param key
     * @param values
     * @param context
     * @throws IOException
     * @throws InterruptedException
     */
    @Override
    protected void reduce(Text key, Iterable values, Reducer.Context context) throws IOException, InterruptedException {
//        super.reduce(key, values, context);
        //        super.reduce(key, values, context);
        long sum =0; //value的和
//    遍历所有的value
        for (LongWritable value : values){
            long v=value.get();
//            累加
            sum+=v;
 
        }
        outValue.set(sum);
        context.write(key,outValue);
    }
}