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Linux下Hadoop hdfs Java API使用
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0 前言
搞了大約2天時間終于把Linux下面Java API的使用給弄清楚了。做個筆記方便以后參考。環境如下所示
Hadoop：2.5.1
Linux：Ubuntu kylin
eclipse：luna
1 步驟
首先是要去下載一個eclipse，這里使用的是Luna。名字比較好聽，代表月亮消滅你們...
然后發現自帶了maven，太棒了！Luna牛掰，毫無疑問創建maven工程，修改pom.xml文件為下面的內容
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<project?xmlns="http://maven.apache.org/POM/4.0.0"?xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"?? ??xsi:schemaLocation="http://maven.apache.org/POM/4.0.0?http://maven.apache.org/xsd/maven-4.0.0.xsd">?? ??<modelVersion>4.0.0</modelVersion>?? ?? ??<groupId>maven</groupId>?? ??<artifactId>maven</artifactId>?? ??<version>0.0.1-SNAPSHOT</version>?? ??<packaging>jar</packaging>?? ?? ??<name>maven</name>?? ??<url>http://maven.apache.org</url>?? ?? ??<properties>?? ????<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>?? ??</properties>?? ?? ??<dependencies>?? ????<dependency>?? ??????<groupId>junit</groupId>?? ??????<artifactId>junit</artifactId>?? ??????<version>3.8.1</version>?? ??????<scope>test</scope>?? ????</dependency>?? ?????<dependency>?? ??????????<groupId>org.apache.hadoop</groupId>?? ??????????<artifactId>hadoop-minicluster</artifactId>?? ??????????<version>2.5.1</version>?? ????</dependency>?? ????<dependency>?? ??????????<groupId>org.apache.hadoop</groupId>?? ??????????<artifactId>hadoop-client</artifactId>?? ??????????<version>2.5.1</version>?? ????</dependency>?? ????<dependency>?? ??????????<groupId>org.apache.hadoop</groupId>?? ??????????<artifactId>hadoop-assemblies</artifactId>?? ??????????<version>2.5.1</version>?? ????</dependency>?? ????????<dependency>?? ??????????<groupId>org.apache.hadoop</groupId>?? ??????????<artifactId>hadoop-maven-plugins</artifactId>?? ??????????<version>2.5.1</version>?? ????</dependency>?? ????????<dependency>?? ??????????<groupId>org.apache.hadoop</groupId>?? ??????????<artifactId>hadoop-common</artifactId>?? ??????????<version>2.5.1</version>?? ????</dependency>?? ????????<dependency>?? ??????????<groupId>org.apache.hadoop</groupId>?? ??????????<artifactId>hadoop-hdfs</artifactId>?? ??????????<version>2.5.1</version>?? ????</dependency>?? ??</dependencies>?? </project>?? 然后等待eclipse maven自動下載依賴的包。等啊等就好了，下一步是配置jvm運行的參數，因為運行的時候需要本地的庫所以必須配置下。我的Hadoop是放在/home/hadoop-master/hadoop-2.5.1下的。
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-Djava.library.path=/home/hadoop-master/hadoop-2.5.1/lib/native?? 因為hadoop2.5.1自己已經編譯好了本地庫所以不用在編譯一次了（這就是用新不用舊的原因，自己編譯太費事兒了。。。。到此一切OK
2 測試代碼
是驢子是馬，拉出來溜溜。寫個小程序跑跑。
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package?maven.maven;?? ?? import?java.io.BufferedReader;?? import?java.io.BufferedWriter;?? import?java.io.File;?? import?java.io.FileInputStream;?? import?java.io.FileNotFoundException;?? import?java.io.IOException;?? import?java.io.InputStream;?? import?java.io.InputStreamReader;?? import?java.io.OutputStreamWriter;?? import?java.io.Writer;?? import?java.util.Date;?? ?? import?org.apache.hadoop.conf.Configuration;?? import?org.apache.hadoop.fs.BlockLocation;?? 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;?? import?org.apache.hadoop.hdfs.DistributedFileSystem;?? import?org.apache.hadoop.hdfs.DFSClient.*;?? import?org.apache.hadoop.hdfs.protocol.DatanodeInfo;?? ?? public?class?HadoopFSOperations?{?? ?????? ????private?static?Configuration?conf?=?new?Configuration();?? ????private?static?final?String?HADOOP_URL="hdfs://192.168.190.129:9000";?? ?????? ????private?static?FileSystem?fs;?? ?????? ????private?static?DistributedFileSystem?hdfs;?? ?????? ????static?{?? ????????try?{?? ????????????FileSystem.setDefaultUri(conf,?HADOOP_URL);?? ????????????fs?=?FileSystem.get(conf);?? ????????????hdfs?=?(DistributedFileSystem)fs;?? ????????}?catch?(Exception?e)?{?? ????????????e.printStackTrace();?? ????????}?? ????}?? ????? ? ?? ????public?void?listDataNodeInfo()?{?????????? ????????try?{?? ????????????DatanodeInfo[]?dataNodeStats?=?hdfs.getDataNodeStats();?? ????????????String[]?names?=?new?String[dataNodeStats.length];?? ????????????System.out.println("List?of?all?the?datanode?in?the?HDFS?cluster:");?? ?????????????? ????????????for?(int?i=0;i<names.length;i++)?{?? ????????????????names[i]?=?dataNodeStats[i].getHostName();?? ????????????????System.out.println(names[i]);?? ????????????}?? ????????????System.out.println(hdfs.getUri().toString());?? ????????}?catch?(Exception?e)?{?? ????????????e.printStackTrace();?? ????????}?? ????}?? ?????? ????? ? ?? ????public?void?checkFileExist()?{?? ????????try?{?? ????????????Path?a=?hdfs.getHomeDirectory();?? ????????????System.out.println("main?path:"+a.toString());?? ?????????????? ????????????Path?f?=?new?Path("/user/xxx/input01/");?? ????????????boolean?exist?=?fs.exists(f);?? ????????????System.out.println("Whether?exist?of?this?file:"+exist);?? ?????????????? ?????????????? ?? ?? ?? ?? ?? ?? ????????}?catch?(Exception?e)?{?? ????????????e.printStackTrace();?? ????????}?? ????}?? ?????? ????? ? ?? ????public?void?createFile()?{?? ????????try?{?? ????????????Path?f?=?new?Path("/user/xxx/input02/file01");?? ????????????System.out.println("Create?and?Write?:"+f.getName()+"?to?hdfs");?? ?????????????? ????????????FSDataOutputStream?os?=?fs.create(f,?true);?? ????????????Writer?out?=?new?OutputStreamWriter(os,?"utf-8");?? ????????????out.write("你好?good?job");?? ????????????out.close();?? ????????????os.close();?? ????????}?catch?(Exception?e)?{?? ????????????e.printStackTrace();?? ????????}?? ????}?? ?????? ?????? ????? ? ? ?? ????public?void?copyFileToHDFS()?{?? ????????try?{?? ????????????Path?f?=?new?Path("/user/xxx/input02/file01");?? ????????????File?file?=?new?File("E:\\hadoopTest\\temporary.txt");?? ?????????????? ????????????FileInputStream?is?=?new?FileInputStream(file);?? ????????????InputStreamReader?isr?=?new?InputStreamReader(is,?"utf-8");?? ????????????BufferedReader?br?=?new?BufferedReader(isr);?? ?????????????? ????????????FSDataOutputStream?os?=?fs.create(f,?true);?? ????????????Writer?out?=?new?OutputStreamWriter(os,?"utf-8");?? ?????????????? ????????????String?str?=?"";?? ????????????while((str=br.readLine())?!=?null)?{?? ????????????????out.write(str+"\n");?? ????????????}?? ????????????br.close();?? ????????????isr.close();?? ????????????is.close();?? ????????????out.close();?? ????????????os.close();?? ????????????System.out.println("Write?content?of?file?"+file.getName()+"?to?hdfs?file?"+f.getName()+"?success");?? ????????}?catch?(Exception?e)?{?? ????????????e.printStackTrace();?? ????????}?? ????}?? ?????? ????? ? ?? ????public?void?getLocation()?{?? ????????try?{?? ????????????Path?f?=?new?Path("/user/xxx/input02/file01");?? ????????????FileStatus?fileStatus?=?fs.getFileStatus(f);?? ?????????????? ????????????BlockLocation[]?blkLocations?=?fs.getFileBlockLocations(fileStatus,?0,?fileStatus.getLen());?? ????????????for?(BlockLocation?currentLocation?:?blkLocations)?{?? ????????????????String[]?hosts?=?currentLocation.getHosts();?? ????????????????for?(String?host?:?hosts)?{?? ????????????????????System.out.println(host);?? ????????????????}?? ????????????}?? ?????????????? ?????????????? ????????????long?modifyTime?=?fileStatus.getModificationTime();?? ????????????Date?d?=?new?Date(modifyTime);?? ????????????System.out.println(d);?? ????????}?catch?(Exception?e)?{?? ????????????e.printStackTrace();?? ????????}?? ????}?? ?????? ????? ? ?? ????public?void?readFileFromHdfs()?{?? ????????try?{?? ????????????Path?f?=?new?Path("/user/xxx/input02/file01");?? ?????????????? ????????????FSDataInputStream?dis?=?fs.open(f);?? ????????????InputStreamReader?isr?=?new?InputStreamReader(dis,?"utf-8");?? ????????????BufferedReader?br?=?new?BufferedReader(isr);?? ????????????String?str?=?"";?? ????????????while?((str?=?br.readLine())?!=null)?{?? ????????????????System.out.println(str);?? ????????????}?? ????????????br.close();?? ????????????isr.close();?? ????????????dis.close();?? ????????}?catch?(Exception?e)?{?? ????????????e.printStackTrace();?? ????????}?? ????}?? ?????? ????? ? ? ? ? ? ?? ????public?void?listFileStatus(String?path)?throws?FileNotFoundException,?IllegalArgumentException,?IOException?{?? ????????FileStatus?fileStatus[]=fs.listStatus(new?Path(path));?? ????????int?listlength=fileStatus.length;?? ????????for?(int?i=0?;i<listlength?;i++){?? ????????????if?(fileStatus[i].isDirectory()?==?false)?{?? ????????????????System.out.println("filename:"?? ????????????????????????+?fileStatus[i].getPath().getName()?+?"\tsize:"?? ????????????????????????+?fileStatus[i].getLen());?? ????????????}?else?{?? ????????????????String?newpath?=?fileStatus[i].getPath().toString();?? ????????????????listFileStatus(newpath);?? ????????????}?? ????????}?? ????}?? ?????? ????public?static?void?main(String[]?args)?{?? ????????HadoopFSOperations?a?=?new?HadoopFSOperations();?? ????????a.listDataNodeInfo();?? ?? ?? ?? ?? ?? ????????try?{?? ????????????a.listFileStatus(HADOOP_URL+"/user");?? ????????}?catch?(FileNotFoundException?e)?{?? ?????????????? ????????????e.printStackTrace();?? ????????}?catch?(IllegalArgumentException?e)?{?? ?????????????? ????????????e.printStackTrace();?? ????????}?catch?(IOException?e)?{?? ?????????????? ????????????e.printStackTrace();?? ????????}?? ????}?? }?? 因為我的hadoop是在192.168.190.129上的所以private static final String HADOOP_URL="hdfs://192.168.190.129:9000";，請酌情修改。搞定跑起來，就能看到下面的結果
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List?of?all?the?datanode?in?the?HDFS?cluster:?? hadoopslaver0?? hadoopslaver2?? hadoopslaver1?? hdfs://192.168.190.129:9000?? filename:TrustCom2015_CFP.pdf???size:290401?? filename:jd.PNG?size:16647?? 可以看到 三個datanode hadoopslaver0,1,2 以及/user下事先放好的文件。小實驗成功
3 總結
在Linux下面Java API就可以按照上面的步驟弄起來了?？偹闶侨f里之行邁出了第一步。
總結
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