hadoop 操作数据库。DBInputFormat，DBOutputFormat

hadoop 操作数据库。DBInputFormat，DBOutputFormat

import java.io.IOException;
import java.util.Iterator;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.lib.db.DBConfiguration;
import org.apache.hadoop.mapred.lib.db.DBInputFormat;
import org.apache.hadoop.mapred.lib.db.DBOutputFormat;

public class DBAccess {
	public static class DBAccessMap extends MapReduceBase implements
			Mapper {
		public void map(LongWritable key, ItemRecord value,
				OutputCollector collector, Reporter reporter)
				throws IOException {
			StringBuilder s = new StringBuilder();
			for (int i = 0; i < value.item.length; i++) {
				if (value.item[i].equals("T"))
					if(s.toString().equals(""))
						s = s.append(String.valueOf(i + 1));
					else
						s=s.append(":"+String.valueOf(i+1));
			}			
			collector.collect(key, new Text(s.toString()));
		}
	}

	public static class DBAccessReduce extends MapReduceBase implements
			Reducer {
		public void reduce(LongWritable key, Iterator value,
				OutputCollector collector, Reporter reporter)
				throws IOException {
			OrderRecord or = new OrderRecord();
			or.id = (int)key.get()+1;
			or.item = value.next().toString();
			collector.collect(or, new Text(or.item));
		}

	}

	public static void main(String[] args) throws Exception {
		JobClient jobclient = new JobClient();
		JobConf conf = new JobConf(DBAccess.class);
		conf.setMapOutputKeyClass(LongWritable.class);
		conf.setMapOutputValueClass(Text.class);
		conf.setOutputKeyClass(OrderRecord.class);
		conf.setOutputValueClass(Text.class);
		conf.setInputFormat(DBInputFormat.class);
		conf.setOutputFormat(DBOutputFormat.class);
		DBConfiguration.configureDB(conf, "com.mysql.jdbc.Driver",
				"jdbc:mysql://localhost/test", "root", "a");
		String[] fields1 = { "id", "item1", "item2", "item3", "item4", "item5",
				"item6", "item7", "item8", "item9", "item10", "item11" };
		DBInputFormat.setInput(conf, ItemRecord.class, "item", null, "id",
				fields1);
		// String[] fields2={"id","item"};
		DBOutputFormat.setOutput(conf, "newitem", "id", "item");
		conf.setMapperClass(DBAccessMap.class);
		conf.setReducerClass(DBAccessReduce.class);
		jobclient.setConf(conf);
		JobClient.runJob(conf);
	}
}