{{{ #!java import java.io.IOException; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; 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; public class HelloHadoop { static public class HelloMapper extends Mapper { public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { // 將出入資料 原封不動的寫入 輸出 context.write((LongWritable) key, (Text) value); } } static public class HelloReducer extends Reducer { public void reduce(LongWritable key, Iterable values, Context context) throws IOException, InterruptedException { Text val = new Text(); // 取回 val 的資料 for (Text str : values) { val.set(str.toString()); } // 將取回的資料引入輸出 context.write(key, val); } } public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException { // 引入 $HADOOP_HOME/conf 內控制檔內的資料 Configuration conf = new Configuration(); // 宣告job 取得conf 並設定名稱 Hadoop Hello World Job job = new Job(conf, "Hadoop Hello World"); // 設定此運算的主程式 job.setJarByClass(HelloHadoop.class); // 設定輸入路徑 FileInputFormat.setInputPaths(job, "/user/hadoop/input"); // 設定輸出路徑 FileOutputFormat.setOutputPath(job, new Path("/user/hadoop/output-hh1")); // 指定定map class job.setMapperClass(HelloMapper.class); // 指定reduce class job.setReducerClass(HelloReducer.class); // 開使運算 job.waitForCompletion(true); } } }}}