} else {
other_args.add(args[i]);
}
} catch (NumberFormatException except) {
System.out.println("ERROR: Integer expected instead of "
+ args[i]);
return printUsage();
} catch (ArrayIndexOutOfBoundsException except) {
System.out.println("ERROR: Required parameter missing from "
+ args[i - 1]);
return printUsage();
}
}
// Make sure there are exactly 2 parameters left.
if (other_args.size() != 2) {
System.out.println("ERROR: Wrong number of parameters: "
+ other_args.size() + " instead of 2.");
return printUsage();
}
FileInputFormat.setInputPaths(conf, other_args.get(0));
FileOutputFormat.setOutputPath(conf, new Path(other_args.get(1)));
JobClient.runJob(conf);
return 0;
}
public static void main(String[] args) throws Exception {
int res = ToolRunner.run(new Configuration(), new WordCount(), args);
System.exit(res);
}
}
2. 保证hadoop集群是配置好了的，单机的也好。新建一个目录，比如 /home/admin/WordCount编译WordCount.java程序。
[html] view plaincopyprint
javac -classpath /home/admin/hadoop/hadoop-0.19.1-core.jar WordCount.java -d /home/admin/WordCount
3. 编译完后在/home/admin/WordCount目录会发现三个class文件 WordCount.class，WordCount$Map.class，WordCount$Reduce.class。
cd 进入 /home/admin/WordCount目录,然后执行：
jar cvf WordCount.jar *.class
就会生成 WordCount.jar 文件。
4. 构造一些输入数据
input1.txt和input2.txt的文件里面是一些单词。如下：
[admin@host WordCount]$ cat input1.txt
Hello, i love china
are you ok
[admin@host WordCount]$ cat input2.txt
hello, i love word
You are ok
在hadoop上新建目录，和put程序运行所需要的输入文件:
hadoop fs -mkdir /tmp/input
hadoop fs -mkdir /tmp/output
hadoop fs -put input1.txt /tmp/input/
hadoop fs -put input2.txt /tmp/input/
5. 运行程序,会显示job运行时的一些信息。
[admin@host WordCount]$ hadoop jar WordCount.jar WordCount /tmp/input /tmp/output
10/09/16 22:49:43 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
10/09/16 22:49:43 INFO mapred.FileInputFormat: Total input paths to process :2
10/09/16 22:49:43 INFO mapred.JobClient: Running job: job_201008171228_76165
10/09/16 22:49:44 INFO mapred.JobClient: map 0% reduce 0%
10/09/16 22:49:47 INFO mapred.JobClient: map 100% reduce 0%
10/09/16 22:49:54 INFO mapred.JobClient: map 100% reduce 100%
10/09/16 22:49:55 INFO mapred.JobClient: Job complete: job_201008171228_76165
10/09/16 22:49:55 INFO mapred.JobClient: Counters: 16
10/09/16 22:49:55 INFO mapred.JobClient: File Systems
10/09/16 22:49:55 INFO mapred.JobClient: HDFS bytes read=62
10/09/16 22:49:55 INFO mapred.JobClient: HDFS bytes written=73
10/09/16 22:49:55 INFO mapred.JobClient: Local bytes read=152
10/09/16 22:49:55 INFO mapred.JobClient: Local bytes written=366
10/09/16 22:49:55 INFO mapred.JobClient: Job Counters
10/09/16 22:49:55 INFO mapred.JobClient: Launched reduce tasks=1
10/09/16 22:49:55 INFO mapred.JobClient: Rack-local map tasks=2
10/09/16 22:49:55 INFO mapred.JobClient: Launched map tasks=2
10/09/16 22:49:55 INFO mapred.JobClient: Map-Reduce Framew