mapreduce--读取mysql数据库数据
import java.io.File;
import java.io.IOException;

import java.io.DataInput;

import java.io.DataOutput;



import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;
import java.util.Iterator;



import org.apache.hadoop.examples.EJob;
import org.apache.hadoop.filecache.DistributedCache;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.io.Writable;

import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.Reducer;

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.FileOutputFormat;

import org.apache.hadoop.mapred.Reporter;

import org.apache.hadoop.mapred.lib.db.DBWritable;

import org.apache.hadoop.mapred.lib.db.DBInputFormat;

import org.apache.hadoop.mapred.lib.db.DBConfiguration;



public class ReadDB {



    public static class Map extends MapReduceBase implements

            Mapper<LongWritable, StudentRecord, LongWritable, Text> {



        // map

        public void map(LongWritable key, StudentRecord value,

        OutputCollector<LongWritable, Text> collector, Reporter reporter)

                throws IOException {

            collector.collect(new LongWritable(value.id),

                    new Text(value.toString()));

        }



    }
    //reducer
       public static class Reduce extends MapReduceBase implements Reducer<LongWritable,Text,LongWritable,Text>{
@Override
public void reduce(LongWritable key, Iterator<Text> value,
OutputCollector<LongWritable,Text> collector, Reporter reporter)
throws IOException {
// TODO Auto-generated method stub
while (value.hasNext()){
collector.collect(key,value.next());
}
}
      
       }



    public static class StudentRecord implements Writable, DBWritable {

        public int id;

        public String name;

        public String sex;

        public int age;



        @Override

        public void readFields(DataInput in) throws IOException {

            this.id = in.readInt();

            this.name = Text.readString(in);

            this.sex = Text.readString(in);

       &nbs