使用mapReduce统计文本中单词个数

上传文件

1 上传文件
hdfs dfs -mkdir /wordfile //创建文件夹
hdfs dfs -put wordcount.txt /wordfile
2 或者代码api

    @Before
    public void setUp() throws URISyntaxException, IOException, InterruptedException {
     

        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://qf");
        conf.set("dfs.nameservices", "qf");
        conf.set("dfs.ha.namenodes.qf", "nn1,nn2");
        conf.set("dfs.namenode.rpc-address.qf.nn1", "192.168.1.6:8020");//nn1表示active状态的namenode
        conf.set("dfs.namenode.rpc-address.qf.nn2", "192.168.1.5:8020");//nn1表示standby状态的namenode

//conf.setBoolean(name, value);
        conf.set("dfs.client.failover.proxy.provider.qf", "org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider");
        fileSystem = FileSystem.get(new URI("hdfs://qf"), conf, "root");
    }
    @Test
    public void upload() throws IOException {
     
        FSDataOutputStream outputStream = fileSystem.create(new Path("/a.txt"),true);
        FileInputStream inputStream = new FileInputStream("d:\\a.txt");
        IOUtils.copy(inputStream,outputStream);
        IOUtils.closeQuietly(inputStream);
        IOUtils.closeQuietly(outputStream);
        fileSystem.close();
    }

书写map

package com.msunsoft.hadoop.Test;

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

import java.io.IOException;
//哪个文字出现了几次
/**
 * k1:偏移量
 * v2:一行中的文字
 * k2:结果的key,即哪个文字
 * v2:结果的数量，即哪个文字出现了几次
 */
public class MapReduceMapOne extends Mapper<LongWritable, Text,Text,LongWritable> {
     
    //map方法就是把k1,v1转化为k2,v2, key表示key1,value表示v2
    //context为上下文，发送给suffer
    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
     
        Text text=new Text();LongWritable longWritable = new LongWritable();
        String[] split = value.toString().split(" ");
        for(String word :split){
     
            text.set(word);
            longWritable.set(1);
            context.write(text,longWritable);
        }
    }
}

书写reduce

package com.msunsoft.hadoop.Test;

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

import java.io.IOException;

public class MapReduceReducerTwo extends Reducer<Text, LongWritable,Text,LongWritable> {
     
    //reduce方法作用，将新的k2和v2转为k3和v3,将k3和v3写入上下文中
    //key表示k2,values表示v2的集合，比如一行中有a,a,b,c 则a有2个，b有1个c有1个，则表示为a:[1,1] b:[1],c:[1]
    @Override
    protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException {
     
        //遍历集合，将集合中的数字相加，得到v3
        long count =0;
        for (LongWritable value:values){
     
            count +=value.get();
        }
        context.write(key,new LongWritable(count));
    }
}

书写job调用main方法

package com.msunsoft.hadoop.Test;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
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.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.ToolRunner;

import javax.lang.model.SourceVersion;
import org.apache.hadoop.util.Tool;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Set;

public class MapReduceJobMainThree extends Configured implements Tool {
     

    //该方法用于指定一个job任务
    @Override
    public int run(String[] strings) throws Exception {
     
        //创建一个job任务对象
        Job job = Job.getInstance(super.getConf(),"wordcount");
        //配置job任务对象(八个步骤)
        job.setInputFormatClass(TextInputFormat.class);//指定输入对象
        TextInputFormat.addInputPath(job,new Path("hdfs://a.txt"));
        //指定map阶段的处理方式
        job.setMapperClass(MapReduceMapOne.class);
        job.setMapOutputKeyClass(Text.class);//设置map阶段key2的类型
        job.setMapOutputValueClass(LongWritable.class);
        //后面中间的步采用默认的方式
        //第7步 指定reduce阶段的处理方式和数据类型
        job.setReducerClass(MapReduceReducerTwo.class);
        //设置k3的类型
        job.setOutputKeyClass(Text.class);
        //设置v3的类型
        job.setOutputValueClass(LongWritable.class);
        //第7步设置输出类型
        job.setOutputFormatClass(TextOutputFormat.class);
        //设置输出的路径,windows为file:///D:\mapreduce\\output
        TextOutputFormat.setOutputPath(job,new Path("hdfs://node5:8020/wordcount.out"));

        //等待任务结束
        boolean bl = job.waitForCompletion(true);
        return bl?0:1;
    }
    //启动job任务
    public static void main(String[] args) throws Exception {
     
        Configuration configuration = new Configuration();
        int run = ToolRunner.run(configuration, new MapReduceJobMainThree(),args);
        System.exit(run);
    }
}

调用方式，打jar包或调用程序main方法

程序调用main方法需要改程序文件路径