HBase自定义MapReduce

HBase表数据的转移

在Hadoop阶段，我们编写的MR任务分别进程了Mapper和Reducer两个类，而在HBase中我们需要继承的是TableMapper和TableReducer两个类。

目标：将fruit表中的一部分数据，通过MR迁入到fruit_mr表中

Step1、构建ReadFruitMapper类，用于读取fruit表中的数据

package com.z.hbase_mr;

import java.io.IOException;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.hbase.util.Bytes;

public class ReadFruitMapper extends TableMapper<ImmutableBytesWritable, Put> {

@Override

protected void map(ImmutableBytesWritable key, Result value, Context context)

throws IOException, InterruptedException {

//将fruit的name和color提取出来，相当于将每一行数据读取出来放入到Put对象中。
Put put = new Put(key.get());

//遍历添加column行
for(Cell cell: value.rawCells()){

//添加/克隆列族:info
if("info".equals(Bytes.toString(CellUtil.cloneFamily(cell)))){

//添加/克隆列：name
if("name".equals(Bytes.toString(CellUtil.cloneQualifier(cell)))){

//将该列cell加入到put对象中
put.add(cell);

//添加/克隆列:color
}else if("color".equals(Bytes.toString(CellUtil.cloneQualifier(cell)))){

//向该列cell加入到put对象中
put.add(cell);
}
}
}

//将从fruit读取到的每行数据写入到context中作为map的输出
context.write(key, put);
}

}

Step2、构建WriteFruitMRReducer类，用于将读取到的fruit表中的数据写入到fruit_mr表中

package com.z.hbase_mr;

import java.io.IOException;

import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableReducer;
import org.apache.hadoop.io.NullWritable;

public class WriteFruitMRReducer extends TableReducer<ImmutableBytesWritable, Put, NullWritable> {

@Override
protected void reduce(ImmutableBytesWritable key, Iterable<Put> values, Context context)
throws IOException, InterruptedException {
//读出来的每一行数据写入到fruit_mr表中

for(Put put: values){

context.write(NullWritable.get(), put);

}
}

}

Step3、构建Fruit2FruitMRJob extends Configured implements Tool，用于组装运行Job任务

//组装Job
public int run(String[] args) throws Exception {

//得到Configuration
Configuration conf = this.getConf();

//创建Job任务
Job job = Job.getInstance(conf, this.getClass().getSimpleName());

job.setJarByClass(Fruit2FruitMRJob.class);

//配置Job
Scan scan = new Scan();

scan.setCacheBlocks(false);

scan.setCaching(500);

//设置Mapper，注意导入的是mapreduce包下的，不是mapred包下的，后者是老版本
TableMapReduceUtil.initTableMapperJob(

"fruit", //数据源的表名

scan, //scan扫描控制器

ReadFruitMapper.class,//设置Mapper类

ImmutableBytesWritable.class,//设置Mapper输出key类型

Put.class,//设置Mapper输出value值类型

job//设置给哪个JOB

);

//设置Reducer

TableMapReduceUtil.initTableReducerJob("fruit_mr", WriteFruitMRReducer.class, job);

//设置Reduce数量，最少1个
job.setNumReduceTasks(1);

boolean isSuccess = job.waitForCompletion(true);

if(!isSuccess){

throw new IOException("Job running with error");

}

return isSuccess ? 0 : 1;

}

Step4、主函数中调用运行该Job任务

public static void main( String[] args ) throws Exception{

Configuration conf = HBaseConfiguration.create();

int status = ToolRunner.run(conf, new Fruit2FruitMRJob(), args);

System.exit(status);

}