HBase-API操作之与MR交互（三）.md

HBase-API操作之与MR交互（三）

目标：将 HBase 的 fruit 表中的数据，通过 MR 筛选处理，导入到 HBase 中的 fruit2 表中

1. 构建 Mapper 类，用于读取 fruit 表中的数据

   package com.yaindream.mr2;
   
   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;
   
   import java.io.IOException;
   
   /**
   * Created with IntelliJ IDEA.
   * User: WangYu
   * Date: 2020/6/15
   * Time: 23:27
   * Description:
   */
   public class Fruit2Mapper extends TableMapper<ImmutableBytesWritable, Put> {
   
       @Override
       protected void map(ImmutableBytesWritable key, Result value, Context context) throws IOException, InterruptedException {
   
           // 构建put对象
           Put put = new Put(key.get());
   
           // 1. 获取数据
           for (Cell cell : value.rawCells()) {
               // 2. 判断当前的cell是否为“name”列
               if ("name".equals(Bytes.toString(CellUtil.cloneQualifier(cell)))) {
                   // 3. 给put对象赋值
                   put.add(cell);
               }
           }
   
           // 4. 写出
           context.write(key, put);
   
       }
   }

2. 构建 Reducer 类，用于将处理过的数据写入到 fruit2 表中

   package com.yaindream.mr2;
   
   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;
   
   import java.io.IOException;
   
   /**
   * Created with IntelliJ IDEA.
   * User: WangYu
   * Date: 2020/6/15
   * Time: 23:27
   * Description:
   */
   public class Fruit2Reducer extends TableReducer<ImmutableBytesWritable, Put, NullWritable> {
   
       @Override
       protected void reduce(ImmutableBytesWritable key, Iterable<Put> values, Context context) throws IOException, InterruptedException {
           // 遍历写出
           for (Put value : values) {
               context.write(NullWritable.get(), value);
           }
       }
   }

3. 构建 Driver 类组装 Job

   package com.yaindream.mr2;
   
   import org.apache.hadoop.conf.Configuration;
   import org.apache.hadoop.hbase.client.Put;
   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.mapreduce.Job;
   import org.apache.hadoop.util.Tool;
   import org.apache.hadoop.util.ToolRunner;
   
   /**
   * Created with IntelliJ IDEA.
   * User: WangYu
   * Date: 2020/6/15
   * Time: 23:27
   * Description:
   */
   public class Fruit2Driver implements Tool {
   
       // 定义配置信息
       private Configuration configuration = null;
   
       public int run(String[] args) throws Exception {
   
           // 1. 获取Job对象
           Job job = Job.getInstance(configuration);
   
           // 2. 设置主类路径
           job.setJarByClass(Fruit2Driver.class);
   
           // 3. 设置 Mapper & 输出KV类型
           TableMapReduceUtil.initTableMapperJob(args[0],
                   new Scan(),
                   Fruit2Mapper.class,
                   ImmutableBytesWritable.class,
                   Put.class,
                   job);
   
           // 4. 设置 Reducer & 输出的表
           TableMapReduceUtil.initTableReducerJob(args[1],
                   Fruit2Reducer.class,
                   job);
   
           // 5. 提交任务
           boolean result = job.waitForCompletion(true);
   
           return result ? 0 : 1;
       }
   
       public void setConf(Configuration conf) {
           configuration = conf;
       }
   
       public Configuration getConf() {
           return configuration;
       }
   
       public static void main(String[] args) {
           try {
               Configuration configuration = new Configuration();
               ToolRunner.run(configuration, new Fruit2Driver(), args);
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   
   }

4. 将程序打包成 Jar 包并上传至集群。方法见 HBase-API操作之与MR交互（二）

5. 运行命令

   [root@hadoop02 hbase-1.3.1]# yarn jar hbase-demo-1.0-SNAPSHOT.jar com.yaindream.mr2.Fruit2Driver fruit fruit2
   

6. 运行结果

   

   可以看到 name 列已经被我们筛选出来了