标签：编译 查看 程序 orm 单词 ges hello 生成 efault
1.编写一个统计单词数量的java程序，并命名为wordcount.java，代码如下：
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; public class WordCount { public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable>{ private final static IntWritable one = new IntWritable(1); private Text word = new Text(); public void map(Object key, Text value, Context context ) throws IOException, InterruptedException { 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> { private IntWritable result = new IntWritable(); public void reduce(Text key, Iterable<IntWritable> values, 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 Exception { Configuration conf = new Configuration(); Job job = Job.getInstance(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); } }
2.声明java环境变量：
export JAVA_HOME=/usr/java/default export PATH=${JAVA_HOME}/bin:${PATH} export HADOOP_CLASSPATH=${JAVA_HOME}/lib/tools.jar
注意：如果不声明以上环境变量，那么在以后运行时，将会收到错误提示：
3.编译并创建jar包。
bin/hadoop com.sun.tools.javac.Main WordCount.java jar cf wc.jar WordCount*.class
4.运行第三步骤生成的wc.jar包。此时要注意，output文件夹不要手工创建，系统运行后会自动创建。
bin/hadoop jar wc.jar WordCount /user/root/wordcount/input /user/root/wordcount/output
正常运行结束后，会在outPut文件夹下生成part-r-00000及__SUCCESS两个文件，其中part-r-00000存储分析结果。运行命令：
bin/hadoop fs -cat /user/joe/wordcount/output/part-r-00000
即可查看分析结果，如下图所示：
至此，本示例完成。
Hadoop版Helloworld之wordcount运行示例
标签：编译 查看 程序 orm 单词 ges hello 生成 efault
原文地址：http://www.cnblogs.com/jizhong/p/6265072.html
