用mapreduce实现将mysql数据导出到HDFS上

因为业务需要，需要将一批mysql数据导入到HBASE，现在先将数据从Mysql导出到HDFS。

版本：hadoop CDH4.5，Hbase-0.946

　　1、实体类

　　　　YqBean 是我的实体类，请根据自己需要修改，实体类需要 implements Writable, DBWritable。

　　2、MR实现

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);  

    }

}