用mapreduce实现将mysql数据导出到HDFS上

import java.io.IOException;
import java.util.Iterator;

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.db.DBConfiguration;
import org.apache.hadoop.mapreduce.lib.db.DBInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;


/**
 * @author
 * @version 创建时间：Jul 24, 2014 2:09:22 AM
 * 类说明
 */
public class AccessData {

    public static class DataAccessMap extends Mapper<LongWritable,YqBean,Text,Text>{
        @Override
        protected void map(LongWritable key, YqBean value,Context context)
                throws IOException, InterruptedException {
                System.out.println(value.toString());
                context.write(new Text(), new Text(value.toString()));
        }
    }
    
    public static class DataAccessReducer extends Reducer<Text,Text,Text,Text>{
        protected void reduce(Text key, Iterable<Text> values,
                Context context)
                throws IOException, InterruptedException {
             for(Iterator<Text> itr = values.iterator();itr.hasNext();)   
             {    
                     context.write(key, itr.next());    
             }   
        }
    }
    public static void main(String[] args) throws Exception {
    
        Configuration conf = new Configuration();   
        //mysql的jdbc驱动
        DBConfiguration.configureDB(conf,"com.mysql.jdbc.Driver", "jdbc:mysql://ip:3306/tablename?useUnicode=true&characterEncoding=utf8", "username", "passwd");    
        Job job = new Job(conf,"test mysql connection");    
        job.setJarByClass(AccessData.class);    
            
        job.setMapperClass(DataAccessMap.class);    
        job.setReducerClass(DataAccessReducer.class);    
            
        job.setOutputKeyClass(Text.class);    
        job.setOutputValueClass(Text.class);    
            
        job.setInputFormatClass(DBInputFormat.class); 
        FileOutputFormat.setOutputPath(job, new Path("hdfs://ip:9000/hdfsFile"));    
            
        //对应数据库中的列名(实体类字段)    
       String[] fields = {"id","title","price","author","quantity","description","category_id","imgUrl"};  
        DBInputFormat.setInput(job, YqBean.class,"tablename", "sql语句 ", "title", fields);      
        System.exit(job.waitForCompletion(true)? 0 : 1);  

  
    }

}