环境：ubuntu14、JAVA_HOME、HADOOP_HOME
环境搭建可见：Ubuntu安装hadoop
1.编写WordCount.java
包含Mapper类和Reducer类
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.LongWritable;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
public class WordCount {
public static class WordCountMap extends
Mapper {
private final IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String line = value.toString();
StringTokenizer token = new StringTokenizer(line);
while (token.hasMoreTokens()) {
word.set(token.nextToken());
context.write(word, one);
}
}
}
public static class WordCountReduce extends
Reducer {
public void reduce(Text key, Iterable values,
Context context) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
context.write(key, new IntWritable(sum));
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = new Job(conf);
job.setJarByClass(WordCount.class);
job.setJobName("wordcount");
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
job.setMapperClass(WordCountMap.class);
job.setReducerClass(WordCountReduce.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.waitForCompletion(true);
}
}
2.编译WordCount.java
语法：
javac
-classpath [包路径1]:[包路径2]
-d [编译的路径] [java的路径]
文件：
java文件：
/opt/data/hadoop/WordCount/WordCount.java
class文件目录 ：
/opt/data/hadoop/WordCount/class
命令：
> javac -classpath /opt/hadoop-1.2.1/hadoop-core-1.2.1.jar:/opt/hadoop-1.2.1/lib/commons-cli-1.2.jar -d class/ WordCount.java
编译后文件：
3.打包
> jar -cvf wordcount.jar *.class
4.作业提交
文件：
两个输入文件：
/opt/data/hadoop/WordCount/input/file1
/opt/data/hadoop/WordCount/input/file2
file1:
hello world hello hadoop hadoop file system hadoop java api hello java
file2:
new file hadoop file hadoop new world hadoop free home hadoop free school
a.hdfs创建路径
> hadoop fs -mkdir input_wordcount
b.传文件到hdfs
> hadoop fs -put input/* input_wordcount/
c.提交作业
> hadoop jar class/wordcount.jar WordCount input_wordcount output_wordcount
d.看看结果
> hadoop fs -s output_wordcount/part-r-00000
结果：
api 1
file 3
free 2
hadoop 7
hello 3
home 1
java 2
new 2
school 1
system 1
world 2
附 命令行：
root@senselyan-virtual-machine: hadoop jar class/wordcount.jar WordCount input_wordcount output_wordcount
17/12/17 16:33:07 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
17/12/17 16:33:07 INFO input.FileInputFormat: Total input paths to process : 2
17/12/17 16:33:07 INFO util.NativeCodeLoader: Loaded the native-hadoop library
17/12/17 16:33:07 WARN snappy.LoadSnappy: Snappy native library not loaded
17/12/17 16:33:07 INFO mapred.JobClient: Running job: job_201712171254_0001
17/12/17 16:33:08 INFO mapred.JobClient: map 0% reduce 0%
17/12/17 16:33:17 INFO mapred.JobClient: map 100% reduce 0%
17/12/17 16:33:25 INFO mapred.JobClient: map 100% reduce 33%
17/12/17 16:33:27 INFO mapred.JobClient: map 100% reduce 100%
17/12/17 16:33:28 INFO mapred.JobClient: Job complete: job_201712171254_0001
17/12/17 16:33:28 INFO mapred.JobClient: Counters: 29
17/12/17 16:33:28 INFO mapred.JobClient: Job Counters
17/12/17 16:33:28 INFO mapred.JobClient: Launched reduce tasks=1
17/12/17 16:33:28 INFO mapred.JobClient: SLOTS_MILLIS_MAPS=13623
17/12/17 16:33:28 INFO mapred.JobClient: Total time spent by all reduces waiting after reserving slots (ms)=0
17/12/17 16:33:28 INFO mapred.JobClient: Total time spent by all maps waiting after reserving slots (ms)=0
17/12/17 16:33:28 INFO mapred.JobClient: Launched map tasks=2
17/12/17 16:33:28 INFO mapred.JobClient: Data-local map tasks=2
17/12/17 16:33:28 INFO mapred.JobClient: SLOTS_MILLIS_REDUCES=9900
17/12/17 16:33:28 INFO mapred.JobClient: File Output Format Counters
17/12/17 16:33:28 INFO mapred.JobClient: Bytes Written=83
17/12/17 16:33:28 INFO mapred.JobClient: FileSystemCounters
17/12/17 16:33:28 INFO mapred.JobClient: FILE_BYTES_READ=301
17/12/17 16:33:28 INFO mapred.JobClient: HDFS_BYTES_READ=383
17/12/17 16:33:28 INFO mapred.JobClient: FILE_BYTES_WRITTEN=156859
17/12/17 16:33:28 INFO mapred.JobClient: HDFS_BYTES_WRITTEN=83
17/12/17 16:33:28 INFO mapred.JobClient: File Input Format Counters
17/12/17 16:33:28 INFO mapred.JobClient: Bytes Read=147
17/12/17 16:33:28 INFO mapred.JobClient: Map-Reduce Framework
17/12/17 16:33:28 INFO mapred.JobClient: Map output materialized bytes=307
17/12/17 16:33:28 INFO mapred.JobClient: Map input records=11
17/12/17 16:33:28 INFO mapred.JobClient: Reduce shuffle bytes=307
17/12/17 16:33:28 INFO mapred.JobClient: Spilled Records=50
17/12/17 16:33:28 INFO mapred.JobClient: Map output bytes=245
17/12/17 16:33:28 INFO mapred.JobClient: Total committed heap usage (bytes)=350224384
17/12/17 16:33:28 INFO mapred.JobClient: CPU time spent (ms)=2510
17/12/17 16:33:28 INFO mapred.JobClient: Combine input records=0
17/12/17 16:33:28 INFO mapred.JobClient: SPLIT_RAW_BYTES=236
17/12/17 16:33:28 INFO mapred.JobClient: Reduce input records=25
17/12/17 16:33:28 INFO mapred.JobClient: Reduce input groups=11
17/12/17 16:33:28 INFO mapred.JobClient: Combine output records=0
17/12/17 16:33:28 INFO mapred.JobClient: Physical memory (bytes) snapshot=615907328
17/12/17 16:33:28 INFO mapred.JobClient: Reduce output records=11
17/12/17 16:33:28 INFO mapred.JobClient: Virtual memory (bytes) snapshot=2537697280
17/12/17 16:33:28 INFO mapred.JobClient: Map output records=25
root@senselyan-virtual-machine: hadoop fs -ls output_wordcount
Found 3 items
-rw-r--r-- 3 root supergroup 0 2017-12-17 16:33 /user/root/output_wordcount/_SUCCESS
drwxr-xr-x - root supergroup 0 2017-12-17 16:33 /user/root/output_wordcount/_logs
-rw-r--r-- 3 root supergroup 83 2017-12-17 16:33 /user/root/output_wordcount/part-r-00000
root@senselyan-virtual-machine: hadoop fs -cat output_wordcount/part-r-00000
Warning: $HADOOP_HOME is deprecated.
api 1
file 3
free 2
hadoop 7
hello 3
home 1
java 2
new 2
school 1
system 1
world 2