之前是用Map/Reduce項目來運作hadoop的，這是直接Run on hadoop的，參見：http://blog.csdn.net/cafebar123/article/details/73611341
下面用java Application 來運作wordcount 程式。
（1）前提條件：
1.eclipse中內建maven插件；
2.eclipse中內建hadoop插件；
3.eclipse中可以運作Map/Reduce項目，并可以得到有效結果。
（2）Maven建構hadoop環境
打開window 指令控制台，輸入：
e:
cd E:\eclipse demo\myHadoop
mvn archetype:generate -DarchetypeGroupId=org.apache.maven.archetypes -DgroupId=org.myhadoop.wordcount -DartifactId=myHadoop -DpackageName=org.myhadoop.wordcount -Dversion=1.0-SNAPSHOT -DinteractiveMode=false
接着看下載下傳界面，如圖：
這樣會建構一個java項目。
（3）安裝需要的jar包。
cd E:\eclipse demo\myHadoop\myHadoop
mvn clean install
（4）将maven建構的java項目導入eclipse中。
（5）在pom.xml 中增加依賴包：
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.myhadoop.wordcount</groupId>
<artifactId>myHadoop</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<hadoop.version>2.7.3</hadoop.version>
</properties>
<name>myHadoop</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.4</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-client</artifactId>
<version>${hadoop.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>${hadoop.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-hdfs</artifactId>
<version>${hadoop.version}</version>
</dependency>
</dependencies>
</project>
（6）繼續下載下傳jar包：
cd E:\eclipse demo\myHadoop\myHadoop
mvn clean install
結果會出現，如圖：
（7）從linux伺服器中下載下傳hadoop配置檔案：
core-site.xml
hdfs-site.xml
mapred-site.xml
建立一個/src/main/resources 目錄，目錄下面建立一個hadoop檔案夾，把配置檔案放進這裡。
（8）配置本地host檔案，
目錄：C:\Windows\System32\drivers\etc
把叢集的master主機ip加進去，
119.29.174.43 master
重新開機電腦。
（9）寫一個wordcount程式，代碼如下：
package org.myhadoop.wordcount;
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
/**
* @ClassName: WordCount2
* @Description: TODO
* @author [email protected]
* @date 2017年6月23日
*
*/
public class WordCount2 {
public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
StringTokenizer itr = new StringTokenizer(value.toString());
while (itr.hasMoreTokens()) {
word.set(itr.nextToken());
context.write(word, one);
}
}
}
public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length != 2) {
System.err.println(otherArgs.length);
System.err.println("Usage: wordcount <in> <out>");
System.exit(2);
}
Job job = new Job(conf, "word count");
job.setJarByClass(WordCount2.class);
job.setMapperClass(TokenizerMapper.class);
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
（10）配置run configuration arguments
參考：http://blog.csdn.net/cafebar123/article/details/73611341
（11）run java application
效果：
（12）問題彙總。
1）
log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Exception in thread "main" org.apache.hadoop.security.AccessControlException: Permission denied: user=zy, access=EXECUTE, inode="/tmp/hadoop-yarn/staging/zy/.staging":root:supergroup:drwx------
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.check(FSPermissionChecker.java:319)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkTraverse(FSPermissionChecker.java:259)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:205)
at org.apache.hadoop.hdfs.server.namenode.FSPermissionChecker.checkPermission(FSPermissionChecker.java:190)
at org.apache.hadoop.hdfs.server.namenode.FSDirectory.checkPermission(FSDirectory.java:1728)
at org.apache.hadoop.hdfs.server.namenode.FSDirStatAndListingOp.getFileInfo(FSDirStatAndListingOp.java:108)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getFileInfo(FSNamesystem.java:3857)
at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.getFileInfo(NameNodeRpcServer.java:1012)
at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getFileInfo(ClientNamenodeProtocolServerSideTranslatorPB.java:843)
at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:982)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2049)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2045)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1698)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2043)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at org.apache.hadoop.ipc.RemoteException.instantiateException(RemoteException.java:106)
at org.apache.hadoop.ipc.RemoteException.unwrapRemoteException(RemoteException.java:73)
at org.apache.hadoop.hdfs.DFSClient.getFileInfo(DFSClient.java:2110)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1305)
at org.apache.hadoop.hdfs.DistributedFileSystem$22.doCall(DistributedFileSystem.java:1301)
at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:1317)
at org.apache.hadoop.fs.FileSystem.exists(FileSystem.java:1426)
at org.apache.hadoop.mapreduce.JobSubmissionFiles.getStagingDir(JobSubmissionFiles.java:116)
at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:144)
at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1290)
at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1287)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Unknown Source)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1698)
at org.apache.hadoop.mapreduce.Job.submit(Job.java:1287)
at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:575)
at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:570)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Unknown Source)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1698)
at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:570)
at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:561)
at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:870)
at org.conan.myhadoop.mr.WordCount.main(WordCount.java:74)
Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.security.AccessControlException): Permission denied: user=zy, access=EXECUTE, inode="/tmp/hadoop-yarn/staging/zy/.staging":root:supergroup:drwx------
hdfs檔案權限問題，解決方法：
1.
export HADOOP_USER_NAME=zy
2.
./bin/hdfs dfs -chmod -R 777 /user/hadoop
3.修改hdfs-site.xml檔案
<property>
<name>dfs.permissions</name>
<value>false</value>
<description></description>
</property>
2)
chmod: changing permissions of '/user/hadoop/miqiLog10000Input': Permission denied. user=zy is not the owner of inode=miqiLog10000Input
這個目錄之前是由root建立的,是以,user=zy不具有修改權限.
可以授權獲得權限:
./bin/hdfs dfs -chown zy /user/Hadoop