MapReduce案例WordCount

<dependencies>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-client</artifactId>
        <version>2.7.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-common</artifactId>
        <version>2.7.3</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-hdfs</artifactId>
        <version>2.7.3</version>
    </dependency>
</dependencies>

<dependencies>

    <dependency>

        <groupId>org.apache.hadoop</groupId>

        <artifactId>hadoop-client</artifactId>

        <version>2.7.3</version>

    </dependency>

    <dependency>

        <groupId>org.apache.hadoop</groupId>

        <artifactId>hadoop-common</artifactId>

        <version>2.7.3</version>

    </dependency>

    <dependency>

        <groupId>org.apache.hadoop</groupId>

        <artifactId>hadoop-hdfs</artifactId>

        <version>2.7.3</version>

    </dependency>

</dependencies>

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

public class WordCountMapper extends Mapper<LongWritable, Text, Text, LongWritable> {

    private Text k = new Text();
    private LongWritable v = new LongWritable();

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String line = value.toString();
        // 分词
        String[] words = line.split(" ");
        // 输出
        for (String word : words) {
            k.set(word);
            v.set(1L);
            context.write(k, v);
        }
    }
}

import java.io.IOException;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Mapper;

public class WordCountMapper extends Mapper<LongWritable, Text, Text, LongWritable> {

    private Text k = new Text();

    private LongWritable v = new LongWritable();

    @Override

    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

        String line = value.toString();

        // 分词

        String[] words = line.split(" ");

        // 输出

        for (String word : words) {

            k.set(word);

            v.set(1L);

            context.write(k, v);

        }

    }

}

import java.io.IOException;

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

public class WordCountReducer extends Reducer<Text, LongWritable, Text, LongWritable> {

    private LongWritable value = new LongWritable();

    @Override
    protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException {
        long sum = 0;
        // 计数
        for (LongWritable v : values) {
            sum += v.get();
        }
        // 输出
        value.set(sum);
        context.write(key, value);
    }
}

import java.io.IOException;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Reducer;

public class WordCountReducer extends Reducer<Text, LongWritable, Text, LongWritable> {

    private LongWritable value = new LongWritable();

    @Override

    protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException {

        long sum = 0;

        // 计数

        for (LongWritable v : values) {

            sum += v.get();

        }

        // 输出

        value.set(sum);

        context.write(key, value);

    }

}

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;

public class Driver {

    public static void main(String[] args) throws Exception {
        args = new String[]{"D:/EclipseWorkspace/mapreducetop10/hello.txt",
            "D:/EclipseWorkspace/mapreducetop10/output"};

        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf);
        // 指明程序的入口
        job.setJarByClass(Driver.class);

        // 指明mapper
        job.setMapperClass(WordCountMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(LongWritable.class);

        // 指明reducer
        job.setReducerClass(WordCountReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);

        // 指明任务的输入输出路径
        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        // 启动任务
        job.waitForCompletion(true);
    }
}

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;

public class Driver {

    public static void main(String[] args) throws Exception {

        args = new String[]{"D:/EclipseWorkspace/mapreducetop10/hello.txt",

            "D:/EclipseWorkspace/mapreducetop10/output"};

        Configuration conf = new Configuration();

        Job job = Job.getInstance(conf);

        // 指明程序的入口

        job.setJarByClass(Driver.class);

        // 指明mapper

        job.setMapperClass(WordCountMapper.class);

        job.setMapOutputKeyClass(Text.class);

        job.setMapOutputValueClass(LongWritable.class);

        // 指明reducer

        job.setReducerClass(WordCountReducer.class);

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(LongWritable.class);

        // 指明任务的输入输出路径

        FileInputFormat.setInputPaths(job, new Path(args[0]));

        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        // 启动任务

        job.waitForCompletion(true);

    }

}