hadoop第一個程序WordCount

hadoop第一個程序WordCount

package test;

import org.apache.hadoop.mapreduce.Job;
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
/*
 * 做者：翟超科
 * 時間：2019.9.3
 * 任務：mapreduce 實現單詞計數
* */
public class WordCount {
    //map類繼承Mapper,實現map功能
    public static class doMapper extends Mapper<Object, Text, Text, IntWritable>{
        //定義變量 one 爲數字1
        public static final IntWritable one = new IntWritable(1);
        //定義關鍵字變量 word
        public static Text word = new Text();
        @Override
        protected void map(Object key, Text value, Mapper<Object, Text, Text, IntWritable>.Context context)
                throws IOException, InterruptedException {
            //將hdfs上的文件按行分割放入tokenzer集合中
            StringTokenizer tokenizer = new StringTokenizer(value.toString(),"\t");
            //將每一行做爲一個關鍵字
            word.set(tokenizer.nextToken());
            //每一個關鍵字出現1次，將鍵值對寫入緩存。
            context.write(word, one);
            
        }
    }
    
    
    //reduce部分整合緩存的鍵值對，
    public static class doReduce extends Reducer<Text, IntWritable, Text, IntWritable>{
        //定義每次讀入的鍵值對的同鍵值對的個數
        private IntWritable result = new IntWritable();
        @Override
        protected void reduce(Text key, Iterable<IntWritable> values, Reducer<Text, IntWritable, Text, IntWritable>.Context context)
                throws IOException, InterruptedException {
            int sum = 0;//定義每一個鍵對應的值只用0個
            for(IntWritable value:values) {
                sum += value.get();
            }
            result.set(sum);
            context.write(key, result);
        }
    }
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        // TODO Auto-generated method stub
        Job job = Job.getInstance();
        job.setJobName("WordCount");
        job.setJarByClass(WordCount.class);
        job.setMapperClass(doMapper.class);
        job.setReducerClass(doReduce.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        Path in = new Path("hdfs://192.168.13.101:9000/data");//文件所處位置
        Path out = new Path("hdfs://192.168.13.101:9000/output");//輸出位置
        FileInputFormat.addInputPath(job,in);
        FileOutputFormat.setOutputPath(job,out);
        System.exit(job.waitForCompletion(true) ? 0 : 1);
        
    }

}