环境：Vmware 8.0 和Ubuntu11.04

Hadoop 实战之运行PutMerge----把本地一组文件合并后复制到HDFS文件

第一步：首先创建一个工程命名为HadoopTest.目录结构如下图:

第二步: 在/home/tanglg1987目录下新建一个start.sh脚本文件，每次启动虚拟机都要删除/tmp目录下的全部文件，重新格式化namenode，代码如下：

sudo rm -rf /tmp/*
rm -rf /home/tanglg1987/hadoop-0.20.2/logs
hadoop namenode -format
hadoop datanode -format
start-all.sh
hadoop fs -mkdir input 
hadoop dfsadmin -safemode leave

第三步：给start.sh增加执行权限并启动hadoop伪分布式集群，代码如下:

chmod 777 /home/tanglg1987/ start.sh
./start.sh 

执行过程如下：

12/10/15 23:05:38 INFO namenode.NameNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG: host = tanglg1987/127.0.1.1
STARTUP_MSG: args = [-format]
STARTUP_MSG: version = 0.20.2
STARTUP_MSG: build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.20 -r 911707; compiled by 'chrisdo' on Fri Feb 19 08:07:34 UTC 2010
************************************************************/
12/10/15 23:05:39 INFO namenode.FSNamesystem: fsOwner=tanglg1987,tanglg1987,adm,dialout,cdrom,plugdev,lpadmin,admin,sambashare
12/10/15 23:05:39 INFO namenode.FSNamesystem: supergroup=supergroup
12/10/15 23:05:39 INFO namenode.FSNamesystem: isPermissionEnabled=true
12/10/15 23:05:39 INFO common.Storage: Image file of size 100 saved in 0 seconds.
12/10/15 23:05:39 INFO common.Storage: Storage directory /tmp/hadoop-tanglg1987/dfs/name has been successfully formatted.
12/10/15 23:05:39 INFO namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at tanglg1987/127.0.1.1
************************************************************/
12/10/15 23:05:40 INFO datanode.DataNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting DataNode
STARTUP_MSG: host = tanglg1987/127.0.1.1
STARTUP_MSG: args = [-format]
STARTUP_MSG: version = 0.20.2
STARTUP_MSG: build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.20 -r 911707; compiled by 'chrisdo' on Fri Feb 19 08:07:34 UTC 2010
************************************************************/
Usage: java DataNode
[-rollback]
12/10/15 23:05:40 INFO datanode.DataNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down DataNode at tanglg1987/127.0.1.1
************************************************************/
starting namenode, logging to /home/tanglg1987/hadoop-0.20.2/bin/../logs/hadoop-tanglg1987-namenode-tanglg1987.out
localhost: starting datanode, logging to /home/tanglg1987/hadoop-0.20.2/bin/../logs/hadoop-tanglg1987-datanode-tanglg1987.out
localhost: starting secondarynamenode, logging to /home/tanglg1987/hadoop-0.20.2/bin/../logs/hadoop-tanglg1987-secondarynamenode-tanglg1987.out
starting jobtracker, logging to /home/tanglg1987/hadoop-0.20.2/bin/../logs/hadoop-tanglg1987-jobtracker-tanglg1987.out
localhost: starting tasktracker, logging to /home/tanglg1987/hadoop-0.20.2/bin/../logs/hadoop-tanglg1987-tasktracker-tanglg1987.out
Safe mode is OFF

第四步：在/home/tanglg1987/input 目录下新建两个文件file01.txt，file02.txt

file01.txt 内容如下：

hello hadoop

file02.txt 内容如下：

hello world

第五步：新建一个PutMerge.java，代码如下：

package com.baison.action;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

public class PutMerge {

public static void main(String[] args) throws IOException {
String [] arg={"/home/tanglg1987/input","hdfs://localhost:9100/user/tanglg1987/output/sum.txt"};
Configuration conf = new Configuration();
FileSystem local = FileSystem.getLocal(conf);
Path inputDir = new Path(arg[0]);
Path hdfsFile = new Path(arg[1]); 
try {
FileStatus[] inputFiles = local.listStatus(inputDir);
FileSystem hdfs = hdfsFile.getFileSystem(conf);
FSDataOutputStream out = hdfs.create(hdfsFile);
for (int i=0; i<inputFiles.length; i++) {
System.out.println(inputFiles[i].getPath().getName());
FSDataInputStream in = local.open(inputFiles[i].getPath());
byte buffer[] = new byte[256];
int bytesRead = 0;
while( (bytesRead = in.read(buffer)) > 0) {
out.write(buffer, 0, bytesRead);
}
in.close();
}
out.close();
} catch (IOException e) {
System.out.println("error:: "+e.getMessage());
e.printStackTrace();
}
}
}

第六步：Run On Hadoop并查看结果集，运行结果如下：