adoop版本：1.1.2
集成开发平台:Eclipse SDK 3.5.1
原创作品，转载请标明：http://blog.csdn.net/yming0221/article/details/9013381
1. 首先定义DFS Location（具体的环境搭建请看前面的博文）
2.下面即是Hello World实例
[java] view plaincopy
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; public class wordcount { 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("Usage: wordcount <in> <out>"); System.exit(2); } Job job = new Job(conf, "word count"); job.setJarByClass(wordcount.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); } }
3. 运行结果
[plain] view plaincopy
13/06/03 14:45:52 INFO input.FileInputFormat: Total input paths to process : 2 13/06/03 14:45:52 WARN snappy.LoadSnappy: Snappy native library not loaded 13/06/03 14:45:52 INFO mapred.JobClient: Running job: job_local_0001 13/06/03 14:45:52 INFO util.ProcessTree: setsid exited with exit code 0 13/06/03 14:45:52 INFO mapred.Task: Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@2b96021e 13/06/03 14:45:52 INFO mapred.MapTask: io.sort.mb = 100 13/06/03 14:45:53 INFO mapred.MapTask: data buffer = 79691776/99614720 13/06/03 14:45:53 INFO mapred.MapTask: record buffer = 262144/327680 13/06/03 14:45:53 INFO mapred.MapTask: Starting flush of map output 13/06/03 14:45:53 INFO mapred.MapTask: Finished spill 0 13/06/03 14:45:53 INFO mapred.Task: Task:attempt_local_0001_m_000000_0 is done. And is in the process of commiting 13/06/03 14:45:53 INFO mapred.LocalJobRunner: 13/06/03 14:45:53 INFO mapred.Task: Task 'attempt_local_0001_m_000000_0' done. 13/06/03 14:45:53 INFO mapred.Task: Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@3621767f 13/06/03 14:45:53 INFO mapred.MapTask: io.sort.mb = 100 13/06/03 14:45:53 INFO mapred.MapTask: data buffer = 79691776/99614720 13/06/03 14:45:53 INFO mapred.MapTask: record buffer = 262144/327680 13/06/03 14:45:53 INFO mapred.MapTask: Starting flush of map output 13/06/03 14:45:53 INFO mapred.MapTask: Finished spill 0 13/06/03 14:45:53 INFO mapred.Task: Task:attempt_local_0001_m_000001_0 is done. And is in the process of commiting 13/06/03 14:45:53 INFO mapred.LocalJobRunner: 13/06/03 14:45:53 INFO mapred.Task: Task 'attempt_local_0001_m_000001_0' done. 13/06/03 14:45:53 INFO mapred.Task: Using ResourceCalculatorPlugin : org.apache.hadoop.util.LinuxResourceCalculatorPlugin@76d6d675 13/06/03 14:45:53 INFO mapred.LocalJobRunner: 13/06/03 14:45:53 INFO mapred.Merger: Merging 2 sorted segments 13/06/03 14:45:53 INFO mapred.Merger: Down to the last merge-pass, with 2 segments left of total size: 53 bytes 13/06/03 14:45:53 INFO mapred.LocalJobRunner: 13/06/03 14:45:53 INFO mapred.JobClient: map 100% reduce 0% 13/06/03 14:45:53 INFO mapred.Task: Task:attempt_local_0001_r_000000_0 is done. And is in the process of commiting 13/06/03 14:45:53 INFO mapred.LocalJobRunner: 13/06/03 14:45:53 INFO mapred.Task: Task attempt_local_0001_r_000000_0 is allowed to commit now 13/06/03 14:45:53 INFO output.FileOutputCommitter: Saved output of task 'attempt_local_0001_r_000000_0' to output 13/06/03 14:45:53 INFO mapred.LocalJobRunner: reduce > reduce 13/06/03 14:45:53 INFO mapred.Task: Task 'attempt_local_0001_r_000000_0' done. 13/06/03 14:45:54 INFO mapred.JobClient: map 100% reduce 100% 13/06/03 14:45:54 INFO mapred.JobClient: Job complete: job_local_0001 13/06/03 14:45:54 INFO mapred.JobClient: Counters: 22 13/06/03 14:45:54 INFO mapred.JobClient: File Output Format Counters 13/06/03 14:45:54 INFO mapred.JobClient: Bytes Written=25 13/06/03 14:45:54 INFO mapred.JobClient: FileSystemCounters 13/06/03 14:45:54 INFO mapred.JobClient: FILE_BYTES_READ=18029 13/06/03 14:45:54 INFO mapred.JobClient: HDFS_BYTES_READ=63 13/06/03 14:45:54 INFO mapred.JobClient: FILE_BYTES_WRITTEN=213880 13/06/03 14:45:54 INFO mapred.JobClient: HDFS_BYTES_WRITTEN=25 13/06/03 14:45:54 INFO mapred.JobClient: File Input Format Counters 13/06/03 14:45:54 INFO mapred.JobClient: Bytes Read=25 13/06/03 14:45:54 INFO mapred.JobClient: Map-Reduce Framework 13/06/03 14:45:54 INFO mapred.JobClient: Reduce input groups=3 13/06/03 14:45:54 INFO mapred.JobClient: Map output materialized bytes=61 13/06/03 14:45:54 INFO mapred.JobClient: Combine output records=4 13/06/03 14:45:54 INFO mapred.JobClient: Map input records=2 13/06/03 14:45:54 INFO mapred.JobClient: Reduce shuffle bytes=0 13/06/03 14:45:54 INFO mapred.JobClient: Physical memory (bytes) snapshot=0 13/06/03 14:45:54 INFO mapred.JobClient: Reduce output records=3 13/06/03 14:45:54 INFO mapred.JobClient: Spilled Records=8 13/06/03 14:45:54 INFO mapred.JobClient: Map output bytes=41 13/06/03 14:45:54 INFO mapred.JobClient: CPU time spent (ms)=0 13/06/03 14:45:54 INFO mapred.JobClient: Total committed heap usage (bytes)=683409408 13/06/03 14:45:54 INFO mapred.JobClient: Virtual memory (bytes) snapshot=0 13/06/03 14:45:54 INFO mapred.JobClient: Combine input records=4 13/06/03 14:45:54 INFO mapred.JobClient: Map output records=4 13/06/03 14:45:54 INFO mapred.JobClient: SPLIT_RAW_BYTES=226 13/06/03 14:45:54 INFO mapred.JobClient: Reduce input records=4
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