* map reduce 內用 setup 初始值實例

{{{
#!java
package ClassCloud;
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<LongWritable, Text, LongWritable, Text> {
		
		String str = "";
		
		public void setup(Context context) {
			Configuration conf = context.getConfiguration();
			this.str = conf.get("gogogo");
			System.err.println("mapper:" + this.str);
		}
		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
			Text val = new Text();
			val.set(this.str);
			context.write((LongWritable) key, val);
		}

	}

	static public class HelloReducer extends
			Reducer<LongWritable, Text, LongWritable, Text> {
		
		String str = "";
		
		public void setup(Context context) {
			Configuration conf = context.getConfiguration();
			this.str = conf.get("gogogo");
			System.err.println("reduce:" + this.str);
		}
		
		public void reduce(LongWritable key, Iterable<Text> values,
				Context context) throws IOException, InterruptedException {
			Text val = new Text();
			// 取回 val 的資料
			for (Text str : values) {
				val.set(str);
			}
			// 將取回的資料引入輸出
//			val.set(values.iterator().toString());
			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();
		conf.set("gogogo", "haha");
		// 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, "text_input");
		// 設定輸出路徑
		FileOutputFormat.setOutputPath(job, new Path("output-hh4"));
		// 指定定map class
		job.setMapperClass(HelloMapper.class);
		// 指定reduce class
		job.setReducerClass(HelloReducer.class);
		// 開使運算
		job.waitForCompletion(true);

	}
}
}}}