一、从Hbase表1中读取数据再把统计结果存到表2

在Hbase中建立相应的表1：

create'hello','cf'

put'hello','1','cf:hui','hello world'

put'hello','2','cf:hui','hello hadoop'

put'hello','3','cf:hui','hello hive'

put'hello','4','cf:hui','hello hadoop'

put'hello','5','cf:hui','hello world'

put'hello','6','cf:hui','hello world'

java代码：

importjava.io.IOException;

importjava.util.Iterator;

importorg.apache.hadoop.conf.Configuration;

importorg.apache.hadoop.hbase.HBaseConfiguration;

importorg.apache.hadoop.hbase.HColumnDescriptor;

importorg.apache.hadoop.hbase.HTableDescriptor;

importorg.apache.hadoop.hbase.client.HBaseAdmin;

importorg.apache.hadoop.hbase.client.Put;

importorg.apache.hadoop.hbase.client.Result;

importorg.apache.hadoop.hbase.client.Scan;

importorg.apache.hadoop.hbase.io.ImmutableBytesWritable;

importorg.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;

importorg.apache.hadoop.hbase.mapreduce.TableMapper;

importorg.apache.hadoop.hbase.mapreduce.TableReducer;

importorg.apache.hadoop.hbase.util.Bytes;

importorg.apache.hadoop.io.IntWritable;

importorg.apache.hadoop.io.NullWritable;

importorg.apache.hadoop.io.Text;

importorg.apache.hadoop.mapreduce.Job;

publicclassHBaseToHbase{

publicstaticvoidmain(String[] args)throwsIOException, ClassNotFoundException, InterruptedException{

String hbaseTableName1 ="hello";

String hbaseTableName2 ="mytb2";

prepareTB2(hbaseTableName2); 

Configuration conf =newConfiguration();

Job job = Job.getInstance(conf); 

job.setJarByClass(HBaseToHbase.class); 

job.setJobName("mrreadwritehbase");

Scan scan =newScan();

scan.setCaching(500);

scan.setCacheBlocks(false);

TableMapReduceUtil.initTableMapperJob(hbaseTableName1, scan, doMapper.class, Text.class, IntWritable.class, job); 

TableMapReduceUtil.initTableReducerJob(hbaseTableName2, doReducer.class, job); 

System.exit(job.waitForCompletion(true) ?1:0);

} 

publicstaticclassdoMapperextendsTableMapper{

privatefinalstaticIntWritable one =newIntWritable(1);

@Override

protectedvoidmap(ImmutableBytesWritable key, Result value, Context context)throwsIOException, InterruptedException{

String rowValue = Bytes.toString(value.list().get(0).getValue());

context.write(newText(rowValue), one);

} 

} 

publicstaticclassdoReducerextendsTableReducer{

@Override

protectedvoidreduce(Text key, Iterable values, Context context)throwsIOException, InterruptedException{

System.out.println(key.toString()); 

intsum =0;

Iterator haha = values.iterator(); 

while(haha.hasNext()) {

sum += haha.next().get(); 

} 

Put put =newPut(Bytes.toBytes(key.toString()));

put.add(Bytes.toBytes("mycolumnfamily"), Bytes.toBytes("count"), Bytes.toBytes(String.valueOf(sum)));

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

} 

} 

publicstaticvoidprepareTB2(String hbaseTableName)throwsIOException{

HTableDescriptor tableDesc =newHTableDescriptor(hbaseTableName);

HColumnDescriptor columnDesc =newHColumnDescriptor("mycolumnfamily");

tableDesc.addFamily(columnDesc); 

Configuration  cfg = HBaseConfiguration.create(); 

HBaseAdmin admin =newHBaseAdmin(cfg);

if(admin.tableExists(hbaseTableName)) {

System.out.println("Table exists,trying drop and create!");

admin.disableTable(hbaseTableName); 

admin.deleteTable(hbaseTableName); 

admin.createTable(tableDesc); 

}else{

System.out.println("create table: "+ hbaseTableName);

admin.createTable(tableDesc); 

} 

} 

} 

在Linux中执行该代码：

[hadoop@h71 q1]$ /usr/jdk1.7.0_25/bin/javac HBaseToHbase.java

[hadoop@h71 q1]$ /usr/jdk1.7.0_25/bin/jar cvf xx.jar HBaseToHbase*class

[hadoop@h71 q1]$ hadoop jar xx.jar HBaseToHbase

查看mytb2表：

hbase(main):009:0> scan'mytb2'

ROW                                                          COLUMN+CELL                                                                                                                                                                   

hello hadoop                                                column=mycolumnfamily:count, timestamp=1489817182454,value=2

hello hive                                                  column=mycolumnfamily:count, timestamp=1489817182454,value=1

hello world                                                 column=mycolumnfamily:count, timestamp=1489817182454,value=3

3row(s)in0.0260seco

作者：清风_d587
链接：https://www.jianshu.com/p/01411078c449