使用MapReduce操作HBase

1 环境准备

1）成功搭建Hadoop-2.2.0开发环境
2）成功启动HBase，通过HBase Shell进行测试
3）使用MyEclipse作为开发工具
4）使用Maven构建项目

2 创建项目

这里我就不带大家如何创建项目了，细节可看HBase Java API 练习中的操作，我们也是使用HBase Java API 练习中的项目。

3 创建上传数据至HBase的类

3.1 WordCountUpLoadToHBase.class

package com.szh.hbase;

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HColumnDescriptor;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.MasterNotRunningException;
import org.apache.hadoop.hbase.ZooKeeperConnectionException;
import org.apache.hadoop.hbase.client.HBaseAdmin;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableReducer;
import org.apache.hadoop.util.Tool;

public class WordCountUpLoadToHBase extends Configured {

    public static class WCHBaseMapper extends Mapper {
        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();
        
        public void map(Object key,Text value,Context context) throws IOException, InterruptedException{
            StringTokenizer strs = new StringTokenizer(value.toString());
            while(strs.hasMoreTokens()){
                word.set(strs.nextToken());
                context.write(new ImmutableBytesWritable(Bytes.toBytes(word.toString())), one);
            }
        }
        
    }
    
    public static class WCHBaseReducer extends TableReducer{
    
        public void reduce(ImmutableBytesWritable key,Iterable values,Context context) throws IOException, InterruptedException{
            int sum = 0;
            for(IntWritable val:values){
                sum += val.get();
            }
            Put put = new Put(key.get());
            put.add(Bytes.toBytes("content"),Bytes.toBytes("count"),Bytes.toBytes(sum+""));
            context.write(key, put);
        }
    }
    
    
    @SuppressWarnings("all")
    public static void main(String[] args) throws MasterNotRunningException, ZooKeeperConnectionException, IOException, ClassNotFoundException, InterruptedException {
        // TODO Auto-generated method stub
        String tableName = "wordcount";
        Configuration conf = HBaseConfiguration.create();
        conf.set("hbase.zookeeper.quorum","szh");
        conf.set("hbase.zookeeper.property.clientPort","2181");
        
        HBaseAdmin admin = new HBaseAdmin(conf);
        //如果表格存在就删除
        if(admin.tableExists(tableName)){
            admin.disableTable(tableName);
            admin.deleteTable(tableName);
        }
        HTableDescriptor tableDescriptor = new HTableDescriptor(tableName);
        HColumnDescriptor columnDescriptor =new HColumnDescriptor("content");
        tableDescriptor.addFamily(columnDescriptor);
        admin.createTable(tableDescriptor);
        
        Job job = new Job(conf,"upload to hbase");
        job.setJarByClass(WordCountUpLoadToHBase.class);
        job.setMapperClass(WCHBaseMapper.class);
        TableMapReduceUtil.initTableReducerJob(tableName, WCHBaseReducer.class, job,null,null,null,null,false);
        
        job.setMapOutputKeyClass(ImmutableBytesWritable.class);
        job.setMapOutputValueClass(IntWritable.class);
        job.setOutputKeyClass(ImmutableBytesWritable.class);
        job.setOutputValueClass(Put.class);
        FileInputFormat.addInputPaths(job, "hdfs://szh:9000/myhbase/hbase-test.txt");
        System.exit(job.waitForCompletion(true)?0:1);
        
    }

}

使用HBase Shell查看执行结果：

使用MapReduce上传数据至HBase.png

4 从HBase获取数据上传至HDFS

4.1 创建MRReadFormHbase.class

package com.szh.hbase;

import java.io.IOException;
import java.util.Map;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class MRReadFromHbase extends Configured {

    public static class WCHBaseMapper extends TableMapper{
        
        @Override
        public void map(ImmutableBytesWritable key,Result values,Context context) throws IOException, InterruptedException{
            StringBuffer sb =new StringBuffer("");
            for(Map.Entry value:values.getFamilyMap("content".getBytes()).entrySet()){
                String  str =new String(value.getValue());
                if(str!=null){
                    sb.append(str);
                }
                context.write(new Text(key.get()), new Text(sb.toString()));
            }
        }
    }
    
    public static class WCHBaseReducer extends Reducer{
        private Text result =new Text();
        public void reduce(Text key,Iterable values,Context context) throws IOException, InterruptedException{
            for(Text val:values){
                result.set(val);
                context.write(key,result);
            }
        }
    }
    
    
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        // TODO Auto-generated method stub
        String tableName = "wordcount";
        Configuration conf =HBaseConfiguration.create();
        conf.set("hbase.zookeeper.quorum", "szh");
        conf.set("hbase.zookeeper.property.clientPort", "2181");
        
        Job job =new Job(conf,"read from hbase to hdfs");
        job.setJarByClass(MRReadFromHbase.class);
        job.setReducerClass(WCHBaseReducer.class);
        TableMapReduceUtil.initTableMapperJob(tableName, new Scan(), WCHBaseMapper.class, Text.class, Text.class, job);
        FileOutputFormat.setOutputPath(job, new Path("hdfs://szh:9000/myhbase/out"));
        System.exit(job.waitForCompletion(true)?0:1);
    }

}

用hdfs命令查看结果：

从HBase读取数据至HDFS