Hadoop的第一个程序 wordcount

待我称王封你为后i 2022-08-02 12:38 208阅读 0赞

**Hadoop的第一个程序 wordcount**

package com.songguoliang.hadoop.chapter05;
    
    import java.io.IOException;
    import java.util.StringTokenizer;
    
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Job;
    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;
    import org.apache.hadoop.util.GenericOptionsParser;
    
    /**
     * 单词计数demo
     * @date 2015-05-01 12:51:29
     * @author sgl
     */
    public class WordCount {
    	/**
    	 * 继承Mapper接口
    	 * @date 2015-05-01 12:53:03
    	 * @author sgl
    	 */
    	public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable>{
    		//one表示单词出现一次
    		private final static IntWritable one=new IntWritable(1);
    		//存储分割的单词
    		private Text word=new Text();
    		@Override
    		protected void map(Object key, Text value, Mapper<Object, Text, Text, IntWritable>.Context context) throws IOException, InterruptedException {
    			StringTokenizer itr=new StringTokenizer(value.toString());
    			while (itr.hasMoreElements()) {
    				word.set(itr.nextToken());
    				context.write(word, one);
    			}
    		}
    		
    		
    	}
    	/**
    	 * Reduce方法
    	 * @date 2015-05-03 19:05:21
    	 * @author sgl
    	 */
    	public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable>{
    		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;
    			for(IntWritable val:values){
    				sum+=val.get();
    			}
    			result.set(sum);
    			context.write(key, result);
    		}
    		
    	}
    	
    	public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
    		Configuration conf=new Configuration();
    		String [] otherArgs=new GenericOptionsParser(conf, args).getRemainingArgs();
    		if(otherArgs.length!=2){
    			System.err.println("Usage:wordcount <in> <out>");
    			System.exit(2);
    		}
    		Job job=new org.apache.hadoop.mapreduce.Job(conf, "word count");
    		job.setJarByClass(WordCount.class);
    		job.setMapperClass(TokenizerMapper.class);
    		job.setCombinerClass(IntSumReducer.class);
    		job.setReducerClass(IntSumReducer.class);
    		job.setOutputKeyClass(Text.class);
    		job.setOutputValueClass(IntWritable.class);
    		FileInputFormat.addInputPath(job, new Path(args[0]));
    		FileOutputFormat.setOutputPath(job, new Path(args[1]));
    		System.exit(job.waitForCompletion(true)?0:1);
    		
    	}
    }