新版API WordCount 小例 及如何导入jar包

WordCount：

简单解析wordcount小例子的代码，对应于新版的API进行处理。

import java.io.IOException;import java.util.StringTokenizer;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.examples.WordCount.TokenizerMapper;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;public class WordCount {/** * @param  * @XD 2014-8-16 */public static class TokenzierMapper extends Mapper<Object,Text,Text,IntWritable>{//对于切下的单词赋予出现频数1private final static IntWritable one = new IntWritable(1);//存储切下的单词private Text word = new Text();public void map(Object key,Text value,Context context) throws IOException, InterruptedException{//StringTokenizer 对输入单词进行切分StringTokenizer itr = new StringTokenizer(value.toString());while(itr.hasMoreTokens()){word.set(itr.nextToken());context.write(word, one);}}}public static class IntSumReducer extends Reducer<Text,IntWritable,Text,IntWritable>{//存取对应单词总频数private IntWritable result = new IntWritable();public  void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException, InterruptedException{//计算频数int sum = 0;for(IntWritable value:values){sum+=value.get();}result.set(sum);//写入输出context.write(key, result);}}public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {// TODO Auto-generated method stub//初始化配置Configuration conf = new Configuration();Job job = new Job(conf,"word count");job.setJarByClass(WordCount.class);//设置map，combine，reduce处理job.setMapperClass(TokenizerMapper.class);job.setReducerClass(IntSumReducer.class);job.setCombinerClass(IntSumReducer.class);//设置输出格式处理类job.setOutputKeyClass(Text.class);job.setOutputValueClass(IntWritable.class);//设置输入输出路径FileInputFormat.addInputPath(job, new Path(args[0]));FileOutputFormat.setOutputPath(job, new Path(args[1]));job.waitForCompletion(true);System.out.println("任务名称: "+job.getJobName());System.out.println("任务成功: "+(job.isSuccessful()?"Yes":"No"));}}

在eclipse中实现此过程，需要先导入自己hadoop安装目录下面的jar包，eclipse导入jar如下：

1.右击工程的根目录，点击Properties进入Properties。或者选中工程根目录，按Alt-Enter即可。

2.在Properties页面中选中Java Build Path，选中Libraries标签，点击Add External JARs。

3.找到需要添加的jar包，确定即可。