以前在學習HBase的時候，也曾想過是否可以在一個MR中同時寫入兩個表，但以前在網上找的時候都找不到比較相關的答案，這兩天又重新找了下，居然有類似的實現，然後就自己參考著寫了下，基本可以運行（本文參考：http://www.wildnove.com/2011/07/19/tutorial-Hadoop-and-hbase-multitableoutputformat/），下面就詳細說下思路：
原始數據如下：
fansy,22,blog.csdu.net/fansy1990
tom,25,blog.csdu.net/tom1987
kate,23,blog.csdu.net/kate1989
jake,20,blog.csdu.net/jake1992
john,35,blog.csdu.net/john1977
ben,30,blog.csdu.net/ben1982
第一列代表name，dierlie代表age，disanlie代表webPage；要做的事情是把name和age存入表1，name和webPage存入表2；下面貼代碼：
ImportToHB.java:
package org.fansy.multipletables;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.MultiTableOutputFormat;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
/**
* write to multiple tables
* @author fansy
*
*/
public class ImportToHB extends Configured implements Tool{
public static void main(String[] args) throws Exception {
int exitCode = ToolRunner.run(new ImportToHB(), args);
System.exit(exitCode);
}
@Override
public int run(String[] args) throws Exception {
if(args.length!=7){
System.err.println("wrong args length:"+args.length);
// System.out.println();
System.out.println("Usage: <input> <table1> <table1-fam> <table1-qua> "+
"<table2> <table2-fam> <table2-qua>");
System.exit(-1);
}
Configuration conf=new Configuration();
conf.set("TABLE1", args[1]);
conf.set("T1-FAM", args[2]);
conf.set("T1-QUA", args[3]);
conf.set("TABLE2", args[4]);
conf.set("T2-FAM", args[5]);
conf.set("T2-QUA", args[6]);
Job job = new Job(conf);
job.setJarByClass(ImportToHB.class);
job.setMapperClass(MapperHB.class);
job.setMapOutputKeyClass(ImmutableBytesWritable.class);
job.setMapOutputValueClass(Writable.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
job.setOutputFormatClass(MultiTableOutputFormat.class);
job.setNumReduceTasks(0);
if(job.waitForCompletion(true)){
return 0;
}
return -1;
}
}
MapperHB.java:
package org.fansy.multipletables;
import java.io.IOException;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.io.*;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.Mapper;
public class MapperHB extends Mapper<LongWritable,Text,ImmutableBytesWritable,Writable>{
private byte[] table1;
private byte[] table2;
private byte[] t1_fam;
private byte[] t1_qua;
private byte[] t2_fam;
private byte[] t2_qua;
public void setup(Context context){
table1=Bytes.toBytes(context.getConfiguration().get("TABLE1"));
table2=Bytes.toBytes(context.getConfiguration().get("TABLE2"));
t1_fam=Bytes.toBytes(context.getConfiguration().get("T1-FAM"));
t1_qua=Bytes.toBytes(context.getConfiguration().get("T1-QUA"));
t2_fam=Bytes.toBytes(context.getConfiguration().get("T2-FAM"));
t2_qua=Bytes.toBytes(context.getConfiguration().get("T2-QUA"));
}
public void map(LongWritable key,Text value,Context context) throws IOException, InterruptedException{
String[] info=value.toString().split(",");
if(info.length!=3){
return;
}
String name=info[0];
String age=info[1];
String webPage=info[2];
// write to the first table row = name+age, value=age;
ImmutableBytesWritable putTable = new ImmutableBytesWritable(table1);
Put put = new Put(Bytes.toBytes(name+","+age));
put.add(t1_fam,t1_qua,Bytes.toBytes(age));
context.write(putTable, put);
// write to the second table row=name+webPage,value=webPage
putTable = new ImmutableBytesWritable(table2);
put = new Put(Bytes.toBytes(name+","+webPage));
put.add(t2_fam,t2_qua,Bytes.toBytes(webPage));
context.write(putTable, put);
}
}
上面的代碼只用了一個Mapper，同時寫入兩個HBase表中。這裡的要點是設置Mapper的輸出key和value的類型，按照上面的代碼類型為：ImmutableBytesWritable和Writable,而且在job的聲明處要設置輸出類型：job.setOutputFormatClass(MultiTableOutputFormat.class);
如何運行上面的程序？
(1)在HBase中創建兩張表:
create 'table1','info'
create 'table2','info'
(2)ImportToHB的輸入參數如下：
hdfs://master:9000/user/fansy/input/info.dat table1 info age table2 info webPage
(3)直接在eclipse中運行
運行後在HBase中察看輸出的數據如下：
