hadoop入门之wordcount小案例

1.创建工程

file->new->other->map/reduce->map/reduce project
->next->project name  -->finish

2.建立工程目录



3.写java文件

3.1WCMapper.java

package hadoop.example.wordcount;

import java.io.IOException;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class WCMapper extends Mapper<LongWritable,Text,Text,LongWritable>{

@Override
protected void map(LongWritable key, Text value,Context context)
throws IOException, InterruptedException {
// TODO Auto-generated method stub
//接收数据
String line = value.toString();
//切分数据
String[] words=line.split(" ");
//循环所有数据
for(String w : words){
// 查询一个记一次
//new Text(w), new LongWritable(1) 将数据进行包装
context.write(new Text(w), new LongWritable(1));
}

}

}

3.2WCReducer.java

package hadoop.example.wordcount;

import java.io.IOException;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

public class WCReducer extends Reducer<Text,LongWritable,Text,LongWritable >{

@Override
protected void reduce(Text key, Iterable<LongWritable> values,
Context context) throws IOException, InterruptedException {
//接受数据
//  Text  key3=key；
//定义一个计数器
long counter=0;
//循values
for(LongWritable l :values){
counter+=l.get();
}
//输出
context.write(key, new LongWritable(counter));

}

}

3.3WordCount.java

package hadoop.example.wordcount;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class WordCount {
public static void main(String args[]) throws IOException, ClassNotFoundException, InterruptedException{
//构建一个job对象
Job job=Job.getInstance(new Configuration());

//action ：main 方法所在的类
job.setJarByClass(WordCount.class);

//设置Mapper的相关属性
job.setMapperClass(WCMapper.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(LongWritable.class);
FileInputFormat.setInputPaths(job, new Path("/root/workplace/hdfs/wdcount/1.txt"));

//设置Reducer的相关的属性
job.setReducerClass(WCReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(LongWritable.class);
FileOutputFormat.setOutputPath(job,new Path("/root/workplace/hdfs/wdcount/output"));

//提交任务
//打印进度详情
job.waitForCompletion(true);

}
}

4.将写好的文件打成jar包

project->e
4000
xport->JAR file->next->在jar file里选择要讲jar放在的目录->next->next->main Class 选择你要在此jar里配置的mian.class->finish

5.上传文件1.txt

hello tom
hello jerry
hello kitty
hello world
hello tom

上传文件
[root@centos ~]# hadoop dfs -put /root/workplace/wdcount  /root/workplace/hdfs
Warning: $HADOOP_HOME is deprecated.

查看文件
[root@centos ~]# hadoop dfs -ls  /root/workplace/hdfs/wdcount/1.txt
Warning: $HADOOP_HOME is deprecated.

Found 1 items
-rw-r--r--   1 root supergroup         57 2016-08-20 09:06 /root/workplace/hdfs/wdcount/1.txt
查看文件详情
[root@centos ~]# hadoop dfs -cat  /root/workplace/hdfs/wdcount/1.txt
Warning: $HADOOP_HOME is deprecated.

hello tom
hello jerry
hello kitty
hello world
hello tom

6.两种执行jar文件的方式

6.1执行jar程序—工作里执行的方式

[root@centos wdcount]# hadoop jar /root/workplace/wdcount/wc.jar
Warning: $HADOOP_HOME is deprecated.

16/08/20 09:20:34 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
16/08/20 09:20:35 INFO input.FileInputFormat: Total input paths to process : 1
16/08/20 09:20:35 INFO util.NativeCodeLoader: Loaded the native-hadoop library
16/08/20 09:20:35 WARN snappy.LoadSnappy: Snappy native library not loaded
16/08/20 09:20:35 INFO mapred.JobClient: Running job: job_201608192017_0008
16/08/20 09:20:36 INFO mapred.JobClient:  map 0% reduce 0%
16/08/20 09:20:43 INFO mapred.JobClient:  map 100% reduce 0%
16/08/20 09:20:52 INFO mapred.JobClient:  map 100% reduce 33%
16/08/20 09:20:54 INFO mapred.JobClient:  map 100% reduce 100%
16/08/20 09:20:56 INFO mapred.JobClient: Job complete: job_201608192017_0008
16/08/20 09:20:56 INFO mapred.JobClient: Counters: 29
16/08/20 09:20:56 INFO mapred.JobClient:   Job Counters
16/08/20 09:20:56 INFO mapred.JobClient:     Launched reduce tasks=1
16/08/20 09:20:56 INFO mapred.JobClient:     SLOTS_MILLIS_MAPS=8719
16/08/20 09:20:56 INFO mapred.JobClient:     Total time spent by all reduces waiting after reserving slots (ms)=0
16/08/20 09:20:56 INFO mapred.JobClient:     Total time spent by all maps waiting after reserving slots (ms)=0
16/08/20 09:20:56 INFO mapred.JobClient:     Launched map tasks=1
16/08/20 09:20:56 INFO mapred.JobClient:     Data-local map tasks=1
16/08/20 09:20:56 INFO mapred.JobClient:     SLOTS_MILLIS_REDUCES=10405
16/08/20 09:20:56 INFO mapred.JobClient:   File Output Format Counters
16/08/20 09:20:56 INFO mapred.JobClient:     Bytes Written=38
16/08/20 09:20:56 INFO mapred.JobClient:   FileSystemCounters
16/08/20 09:20:56 INFO mapred.JobClient:     FILE_BYTES_READ=162
16/08/20 09:20:56 INFO mapred.JobClient:     HDFS_BYTES_READ=177
16/08/20 09:20:56 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=110365
16/08/20 09:20:56 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=38
16/08/20 09:20:56 INFO mapred.JobClient:   File Input Format Counters
16/08/20 09:20:56 INFO mapred.JobClient:     Bytes Read=57
16/08/20 09:20:56 INFO mapred.JobClient:   Map-Reduce Framework
16/08/20 09:20:56 INFO mapred.JobClient:     Map output materialized bytes=162
16/08/20 09:20:56 INFO mapred.JobClient:     Map input records=5
16/08/20 09:20:56 INFO mapred.JobClient:     Reduce shuffle bytes=162
16/08/20 09:20:56 INFO mapred.JobClient:     Spilled Records=20
16/08/20 09:20:56 INFO mapred.JobClient:     Map output bytes=136
16/08/20 09:20:56 INFO mapred.JobClient:     Total committed heap usage (bytes)=158797824
16/08/20 09:20:56 INFO mapred.JobClient:     CPU time spent (ms)=2290
16/08/20 09:20:56 INFO mapred.JobClient:     Combine input records=0
16/08/20 09:20:56 INFO mapred.JobClient:     SPLIT_RAW_BYTES=120
16/08/20 09:20:56 INFO mapred.JobClient:     Reduce input records=10
16/08/20 09:20:56 INFO mapred.JobClient:     Reduce input groups=5
16/08/20 09:20:56 INFO mapred.JobClient:     Combine output records=0
16/08/20 09:20:56 INFO mapred.JobClient:     Physical memory (bytes) snapshot=263684096
16/08/20 09:20:56 INFO mapred.JobClient:     Reduce output records=5
16/08/20 09:20:56 INFO mapred.JobClient:     Virtual memory (bytes) snapshot=3726540800
16/08/20 09:20:56 INFO mapred.JobClient:     Map output records=10
----------------------
执行jar程序完成查看执行结果
[root@centos wdcount]# hadoop dfs -ls /root/workplace/hdfs/wdcount/output
Warning: $HADOOP_HOME is deprecated.

Found 3 items
-rw-r--r--   1 root supergroup          0 2016-08-20 09:20 /root/workplace/hdfs/wdcount/output/_SUCCESS
drwxr-xr-x   - root supergroup          0 2016-08-20 09:20 /root/workplace/hdfs/wdcount/output/_logs
-rw-r--r--   1 root supergroup         38 2016-08-20 09:20 /root/workplace/hdfs/wdcount/output/part-r-00000
[root@centos wdcount]# hadoop dfs -cat  /root/workplace/hdfs/wdcount/output/part-r-00000
Warning: $HADOOP_HOME is deprecated.

hello   5
jerry   1
kitty   1
tom 2
world   1
[root@centos wdcount]#

6.2执行程序的另外一种方法

控制台的输出
16/08/20 10:32:12 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
16/08/20 10:32:12 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
16/08/20 10:32:12 WARN mapred.JobClient: No job jar file set.  User classes may not be found. See JobConf(Class) or JobConf#setJar(String).
16/08/20 10:32:12 INFO input.FileInputFormat: Total input paths to process : 1
16/08/20 10:32:13 WARN snappy.LoadSnappy: Snappy native library not loaded
16/08/20 10:32:13 INFO mapred.JobClient: Running job: job_local288352385_0001
16/08/20 10:32:13 INFO mapred.LocalJobRunner: Waiting for map tasks
16/08/20 10:32:13 INFO mapred.LocalJobRunner: Starting task: attempt_local288352385_0001_m_000000_0
16/08/20 10:32:13 INFO util.ProcessTree: setsid exited with exit code 0
16/08/20 10:32:13 INFO mapred.Task:  Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@68fa8cf9
16/08/20 10:32:13 INFO mapred.MapTask: Processing split: hdfs://localhost:9000/root/workplace/hdfs/wdcount/1.txt:0+57
16/08/20 10:32:14 INFO mapred.MapTask: io.sort.mb = 100
16/08/20 10:32:14 INFO mapred.MapTask: data buffer = 79691776/99614720
16/08/20 10:32:14 INFO mapred.MapTask: record buffer = 262144/327680
16/08/20 10:32:14 INFO mapred.MapTask: Starting flush of map output
16/08/20 10:32:14 INFO mapred.MapTask: Finished spill 0
16/08/20 10:32:14 INFO mapred.Task: Task:attempt_local288352385_0001_m_000000_0 is done. And is in the process of commiting
16/08/20 10:32:14 INFO mapred.LocalJobRunner:
16/08/20 10:32:14 INFO mapred.Task: Task 'attempt_local288352385_0001_m_000000_0' done.
16/08/20 10:32:14 INFO mapred.LocalJobRunner: Finishing task: attempt_local288352385_0001_m_000000_0
16/08/20 10:32:14 INFO mapred.LocalJobRunner: Map task executor complete.
16/08/20 10:32:14 INFO mapred.Task:  Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@384f27a1
16/08/20 10:32:14 INFO mapred.LocalJobRunner:
16/08/20 10:32:14 INFO mapred.Merger: Merging 1 sorted segments
16/08/20 10:32:14 INFO mapred.Merger: Down to the last merge-pass, with 1 segments left of total size: 158 bytes
16/08/20 10:32:14 INFO mapred.LocalJobRunner:
16/08/20 10:32:14 INFO mapred.Task: Task:attempt_local288352385_0001_r_000000_0 is done. And is in the process of commiting
16/08/20 10:32:14 INFO mapred.LocalJobRunner:
16/08/20 10:32:14 INFO mapred.Task: Task attempt_local288352385_0001_r_000000_0 is allowed to commit now
16/08/20 10:32:14 INFO output.FileOutputCommitter: Saved output of task 'attempt_local288352385_0001_r_000000_0' to hdfs://localhost:9000/root/workplace/hdfs/wdcount/output
16/08/20 10:32:14 INFO mapred.LocalJobRunner: reduce > reduce
16/08/20 10:32:14 INFO mapred.Task: Task 'attempt_local288352385_0001_r_000000_0' done.
16/08/20 10:32:14 INFO mapred.JobClient:  map 100% reduce 100%
16/08/20 10:32:14 INFO mapred.JobClient: Job complete: job_local288352385_0001
16/08/20 10:32:14 INFO mapred.JobClient: Counters: 22
16/08/20 10:32:14 INFO mapred.JobClient:   File Output Format Counters
16/08/20 10:32:14 INFO mapred.JobClient:     Bytes Written=38
16/08/20 10:32:14 INFO mapred.JobClient:   File Input Format Counters
16/08/20 10:32:14 INFO mapred.JobClient:     Bytes Read=57
16/08/20 10:32:14 INFO mapred.JobClient:   FileSystemCounters
16/08/20 10:32:14 INFO mapred.JobClient:     FILE_BYTES_READ=510
16/08/20 10:32:14 INFO mapred.JobClient:     HDFS_BYTES_READ=114
16/08/20 10:32:14 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=136042
16/08/20 10:32:14 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=38
16/08/20 10:32:14 INFO mapred.JobClient:   Map-Reduce Framework
16/08/20 10:32:14 INFO mapred.JobClient:     Reduce input groups=5
16/08/20 10:32:14 INFO mapred.JobClient:     Map output materialized bytes=162
16/08/20 10:32:14 INFO mapred.JobClient:     Combine output records=0
16/08/20 10:32:14 INFO mapred.JobClient:     Map input records=5
16/08/20 10:32:14 INFO mapred.JobClient:     Reduce shuffle bytes=0
16/08/20 10:32:14 INFO mapred.JobClient:     Physical memory (bytes) snapshot=0
16/08/20 10:32:14 INFO mapred.JobClient:     Reduce output records=5
16/08/20 10:32:14 INFO mapred.JobClient:     Spilled Records=20
16/08/20 10:32:14 INFO mapred.JobClient:     Map output bytes=136
16/08/20 10:32:14 INFO mapred.JobClient:     Total committed heap usage (bytes)=258482176
16/08/20 10:32:14 INFO mapred.JobClient:     CPU time spent (ms)=0
16/08/20 10:32:14 INFO mapred.JobClient:     Virtual memory (bytes) snapshot=0
16/08/20 10:32:14 INFO mapred.JobClient:     SPLIT_RAW_BYTES=120
16/08/20 10:32:14 INFO mapred.JobClient:     Map output records=10
16/08/20 10:32:14 INFO mapred.JobClient:     Combine input records=0
16/08/20 10:32:14 INFO mapred.JobClient:     Reduce input records=10

7.完成wrodcount案例

8.HDFS的一些基本操作

删除文件夹的操作

[root@centos ~]# hadoop dfs -rmr /root/workplace/wdcount
Warning: $HADOOP_HOME is deprecated.

Deleted hdfs://localhost:9000/root/workplace/wdcount

查看文件的操作

[root@centos ~]# hadoop dfs -ls  /root/workplace/hdfs/wdcount/1.txt
Warning: $HADOOP_HOME is deprecated.

Found 1 items
-rw-r--r--   1 root supergroup         57 2016-08-20 09:06 /root/workplace/hdfs/wdcount/1.txt

查看文件的详情

[root@centos ~]# hadoop dfs -cat  /root/workplace/hdfs/wdcount/1.txt
Warning: $HADOOP_HOME is deprecated.

hello tom
hello jerry
hello kitty
hello world
hello tom

删除文件夹下的所有的东西

[root@centos ~]# hadoop dfs -rm /root/workplace/wdcount/*
Warning: $HADOOP_HOME is deprecated.

Deleted hdfs://localhost:9000/root/workplace/wdcount/1.txt
Deleted hdfs://localhost:9000/root/workplace/wdcount/1.txt~
Deleted hdfs://localhost:9000/root/workplace/wdcount/wc.jar

将本地文件上传到HDFS文件系统

[root@centos ~]# hadoop dfs -put /root/workplace/wdcount/1.txt  /root/workplace/hdfs/wdcount
Warning: $HADOOP_HOME is deprecated.

[root@centos ~]# hadoop dfs -ls  /root/workplace/hdfs/wdcount
Warning: $HADOOP_HOME is deprecated.

Found 1 items
-rw-r--r--   1 root supergroup         57 2016-08-20 09:02 /root/workplace/hdfs/wdcount