使用maven搭建hadoop環境
阿新 • • 發佈：2019-01-08
關於Maven的使用就不再囉嗦了，網上很多，並且這麼多年變化也不大，這裡僅介紹怎麼搭建Hadoop的開發環境。
1. 首先建立工程
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mvn archetype:generate -DgroupId=my.hadoopstudy -DartifactId=hadoopstudy -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false - 然後在pom.xml檔案裡新增hadoop的依賴包hadoop-common, hadoop-client, hadoop-hdfs，新增後的pom.xml檔案如下
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<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion - 測試
3.1 首先我們可以測試一下hdfs的開發，這裡假定使用上一篇Hadoop文章中的hadoop叢集，類程式碼如下
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package my.hadoopstudy.dfs;
import org.apache.hadoop.conf.Configuration;
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.io.IOUtils;
import java.io.InputStream;
import java.net.URI;
public class Test {
public static void main(String[] args) throws Exception {
String uri = "hdfs://9.111.254.189:9000/";
Configuration config = new Configuration();
FileSystem fs = FileSystem.get(URI.create(uri), config);
// 列出hdfs上/user/fkong/目錄下的所有檔案和目錄
FileStatus[] statuses = fs.listStatus(new Path("/user/fkong"));
for (FileStatus status : statuses) {
System.out.println(status);
}
// 在hdfs的/user/fkong目錄下建立一個檔案，並寫入一行文字
FSDataOutputStream os = fs.create(new Path("/user/fkong/test.log"));
os.write("Hello World!".getBytes());
os.flush();
os.close();
// 顯示在hdfs的/user/fkong下指定檔案的內容
InputStream is = fs.open(new Path("/user/fkong/test.log"));
IOUtils.copyBytes(is, System.out, 1024, true);
}
} 3.2 測試MapReduce作業
測試程式碼比較簡單，如下：
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package my.hadoopstudy.mapreduce;
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;
import java.io.IOException;
public class EventCount {
public static class MyMapper extends Mapper<Object, Text, Text, IntWritable>{
private final static IntWritable one = new IntWritable(1);
private Text event = new Text();
public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
int idx = value.toString().indexOf(" ");
if (idx > 0) {
String e = value.toString().substring(0, idx);
event.set(e);
context.write(event, one);
}
}
}
public static class MyReducer 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("Usage: EventCount <in> <out>");
System.exit(2);
}
Job job = Job.getInstance(conf, "event count");
job.setJarByClass(EventCount.class);
job.setMapperClass(MyMapper.class);
job.setCombinerClass(MyReducer.class);
job.setReducerClass(MyReducer.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);
}
} 執行“mvn package”命令產生jar包hadoopstudy-1.0-SNAPSHOT.jar，並將jar檔案複製到hadoop安裝目錄下
這裡假定我們需要分析幾個日誌檔案中的Event資訊來統計各種Event個數，所以建立一下目錄和檔案
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/tmp/input/event.log.1
/tmp/input/event.log.2
/tmp/input/event.log.3
因為這裡只是要做一個列子，所以每個檔案內容可以都一樣，假如內容如下
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JOB_NEW ...
JOB_NEW ...
JOB_FINISH ...
JOB_NEW ...
JOB_FINISH ... 然後把這些檔案複製到HDFS上
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$ bin/hdfs dfs -put /tmp/input /user/fkong/input
執行mapreduce作業
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$ bin/hadoop jar hadoopstudy-1.0-SNAPSHOT.jar my.hadoopstudy.mapreduce.EventCount /user/fkong/input /user/fkong/output檢視執行結果
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$ bin/hdfs dfs -cat /user/fkong/output/part-r-00000