MapRedure实战单词统计

官方文档中有对应的例子

1、在本地程序目录建立文件test单词和路径如下：

Paste_Image.png

2、在hdfs中建立input/wc文件夹然后上传文件到test到改目录下

Paste_Image.png

3、maper类的编写

package com.topwqp.mr;

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

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


/**
 * LongWritable 和  Long对应
 * Text和String对应
 * 四个参数：前两个是输入类型（对于单词统计，输入就是 单词编号(LongWritable) ，单词(Text)）
 * 后两个是输出类型（对于单词统计，输出就是单词(Text)和个数(LongWritable)）
 * @author wqp
 *
 */
public class WcMapper extends Mapper{
    //线程启动真正调用的方法
    /**这是整个mapper的过程，单词拆分
     * 前两个参数是输入数据
     * 第二个参数就是context
     * 每次调用map方法会传入split中一行数据key:该行数据所在文件中的位置下标，value为这行数据
     */
    @Override
    protected void map(LongWritable key, Text value,
            Context context)
            throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        
        String line = value.toString(); //获取一行数据
        StringTokenizer st = new StringTokenizer(line); //按照空格进行拆分后的单词
        
        while(st.hasMoreTokens()){
            String word = st.nextToken();//每一个单词
            //进行输出
            context.write(new Text(word), new IntWritable(1));//map输出
        }
    }

}

4、reducer类的编写

package com.topwqp.mr;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
/**
 * 输入的数据就是mapper的输出
 * @author wqp
 *
 */
public class WcReducer extends Reducer{
  @Override
protected void reduce(Text key, Iterable iterable,
        Context context)
        throws IOException, InterruptedException {
    // TODO Auto-generated method stub
    
    int sum = 0;
    //每一个相当于这种方式： example WORD [1,1,1,1,3,2] 所以计算如下
    for(IntWritable i:iterable){
        sum = sum + i.get();
    }
    context.write(key, new IntWritable(sum));
}
}

5、Job类编写

package com.topwqp.mr;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
/**
 * 对应的jobtracker
 * @author wqp
 *
 */
public class JobRun {
  public static void main(String[] args) {
    //configuration中配置的key value和  配置文件下的conf/mapred-site.xml保持一致
    Configuration conf = new Configuration();
    conf.set("mapred.job.tracker", "localhost:9001");
    try{
        Job job = new Job(conf);
        //当前类是运行入口
        job.setJarByClass(JobRun.class);
        //mapper类
        job.setMapperClass(WcMapper.class);
        //reducer类
        job.setReducerClass(WcReducer.class);
        //最终统计结果输出类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);
        
        job.setNumReduceTasks(1);//设置reduce任务的个数，默认是一个
        //mapreduce 输入数据所在的目录或者文件
        FileInputFormat.addInputPath(job, new Path("/Users/wangqiupeng/Documents/xplan/bigdata/data/hadoop-1.2.1/input/wc/"));
        //mapreduce执行之后的输出数据的目录 这个输出路径的部分目录可以没有，如果没有会自动创建
        FileOutputFormat.setOutputPath(job, new Path("/Users/wangqiupeng/Documents/xplan/bigdata/data/hadoop-1.2.1/output/wc/"));
        
        //等待job完成退出
        System.exit(job.waitForCompletion(true) ? 0 :1);
        
    }catch(Exception e){
        e.printStackTrace();
    }
}
}

打包运行：

打包应用程序上传到执行服务器，由于我本机是伪分布式，所以就在我本机上执行，注意如果是分布式，打包后的jar包应该放在mapred-site.xml中的mapred.job.tracker中配置的参数的机器上

打包以后再hadoop/bin目录下执行：ss:bin wqp$ ./hadoop jar /Users/wangqiupeng/Downloads/wc.jar com.topwqp.mr.JobRun

因为输入为：

Paste_Image.png

所以
执行成功后统计单词个数输出：

Paste_Image.png

以上成功统计出单词个数

导出jar包：

dabao.png

执行完成后的输出信息：

ss:bin wqp$ ./hadoop jar /Users/wangqiupeng/Downloads/wc.jar com.topwqp.mr.JobRun
16/08/20 00:37:01 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
16/08/20 00:37:01 INFO input.FileInputFormat: Total input paths to process : 1
16/08/20 00:37:01 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
16/08/20 00:37:01 WARN snappy.LoadSnappy: Snappy native library not loaded
16/08/20 00:37:01 INFO mapred.JobClient: Running job: job_201608200016_0006
16/08/20 00:37:02 INFO mapred.JobClient:  map 0% reduce 0%
16/08/20 00:37:06 INFO mapred.JobClient:  map 100% reduce 0%
16/08/20 00:37:13 INFO mapred.JobClient:  map 100% reduce 33%
16/08/20 00:37:14 INFO mapred.JobClient:  map 100% reduce 100%
16/08/20 00:37:14 INFO mapred.JobClient: Job complete: job_201608200016_0006
16/08/20 00:37:14 INFO mapred.JobClient: Counters: 26
16/08/20 00:37:14 INFO mapred.JobClient:   Job Counters
16/08/20 00:37:14 INFO mapred.JobClient:     Launched reduce tasks=1
16/08/20 00:37:14 INFO mapred.JobClient:     SLOTS_MILLIS_MAPS=3148
16/08/20 00:37:14 INFO mapred.JobClient:     Total time spent by all reduces waiting after reserving slots (ms)=0
16/08/20 00:37:14 INFO mapred.JobClient:     Total time spent by all maps waiting after reserving slots (ms)=0
16/08/20 00:37:14 INFO mapred.JobClient:     Launched map tasks=1
16/08/20 00:37:14 INFO mapred.JobClient:     Data-local map tasks=1
16/08/20 00:37:14 INFO mapred.JobClient:     SLOTS_MILLIS_REDUCES=8142
16/08/20 00:37:14 INFO mapred.JobClient:   File Output Format Counters
16/08/20 00:37:14 INFO mapred.JobClient:     Bytes Written=49
16/08/20 00:37:14 INFO mapred.JobClient:   FileSystemCounters
16/08/20 00:37:14 INFO mapred.JobClient:     FILE_BYTES_READ=128
16/08/20 00:37:14 INFO mapred.JobClient:     HDFS_BYTES_READ=222
16/08/20 00:37:14 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=132952
16/08/20 00:37:14 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=49
16/08/20 00:37:14 INFO mapred.JobClient:   File Input Format Counters
16/08/20 00:37:14 INFO mapred.JobClient:     Bytes Read=62
16/08/20 00:37:14 INFO mapred.JobClient:   Map-Reduce Framework
16/08/20 00:37:14 INFO mapred.JobClient:     Reduce input groups=6
16/08/20 00:37:14 INFO mapred.JobClient:     Map output materialized bytes=128
16/08/20 00:37:14 INFO mapred.JobClient:     Combine output records=0
16/08/20 00:37:14 INFO mapred.JobClient:     Map input records=3
16/08/20 00:37:14 INFO mapred.JobClient:     Reduce shuffle bytes=128
16/08/20 00:37:14 INFO mapred.JobClient:     Reduce output records=6
16/08/20 00:37:14 INFO mapred.JobClient:     Spilled Records=20
16/08/20 00:37:14 INFO mapred.JobClient:     Map output bytes=102
16/08/20 00:37:14 INFO mapred.JobClient:     Total committed heap usage (bytes)=308281344
16/08/20 00:37:14 INFO mapred.JobClient:     Combine input records=0
16/08/20 00:37:14 INFO mapred.JobClient:     Map output records=10
16/08/20 00:37:14 INFO mapred.JobClient:     SPLIT_RAW_BYTES=160
16/08/20 00:37:14 INFO mapred.JobClient:     Reduce input records=10

任务显示执行过的任务

Paste_Image.png