欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  数据库

hadoop wordcount新API例子

程序员文章站 2022-03-20 09:30:06
...

准备 准备一些输入文件,可以用hdfs dfs -put xxx/*?/user/fatkun/input上传文件 代码 package com.fatkun;?import java.io.IOException;import java.util.ArrayList;import java.util.List;import java.util.StringTokenizer;?import org.apache.commons.lo

准备

准备一些输入文件,可以用hdfs dfs -put xxx/*?/user/fatkun/input上传文件

代码

package com.fatkun;
?
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
?
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
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.Tool;
import org.apache.hadoop.util.ToolRunner;
?
public class WordCount extends Configured implements Tool {
    static enum Counters {
        INPUT_WORDS // 计数器
    } 
?
    static Log logger = LogFactory.getLog(WordCount.class);
?
    public static class CountMapper extends
            Mapper {
        private final IntWritable one = new IntWritable(1);
        private Text word = new Text();
        private boolean caseSensitive = true;
?
        @Override
        protected void setup(Context context) throws IOException,
                InterruptedException {
            // 读取配置
            Configuration conf = context.getConfiguration();
            caseSensitive = conf.getBoolean("wordcount.case.sensitive", true);
            super.setup(context);
        }
?
        @Override
        protected void map(LongWritable key, Text value, Context context)
                throws IOException, InterruptedException {
            StringTokenizer itr = new StringTokenizer(value.toString());
            while (itr.hasMoreTokens()) {
                if (caseSensitive) { // 是否大小写敏感
                    word.set(itr.nextToken());
                } else {
                    word.set(itr.nextToken().toLowerCase());
                }
                context.write(word, one);
                context.getCounter(Counters.INPUT_WORDS).increment(1);
            }
        }
    }
?
    public static class CountReducer extends
            Reducer {
?
        @Override
        protected void reduce(Text text, Iterable values,
                Context context) throws IOException, InterruptedException {
            int sum = 0;
            for (IntWritable value : values) {
                sum += value.get();
            }
            context.write(text, new IntWritable(sum));
        }
?
    }
?
    @Override
    public int run(String[] args) throws Exception {
        Configuration conf = new Configuration(getConf());
        Job job = Job.getInstance(conf, "Example Hadoop WordCount");
        job.setJarByClass(WordCount.class);
        job.setMapperClass(CountMapper.class);
        job.setCombinerClass(CountReducer.class);
        job.setReducerClass(CountReducer.class);
?
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
?
        List other_args = new ArrayList();
        for (int i = 0; i 

运行

在eclipse导出jar包,执行以下命令

hadoop jar wordcount.jar com.fatkun.WordCount -Dwordcount.case.sensitive=false /user/fatkun/input /user/fatkun/output

参考

http://cxwangyi.blogspot.com/2009/12/wordcount-tutorial-for-hadoop-0201.html

http://hadoop.apache.org/docs/r1.2.1/mapred_tutorial.html#Example%3A+WordCount+v2.0