從無代碼的java代碼調用hadoop作業

我使用此代碼來運行字數hadoop作業。當我使用hadoop eclipse插件從eclipse內部運行WordCountDriver時，WordCountDriver會運行。當我將mapper和reducer類打包爲jar並將其放到classpath中時，WordCountDriver也從命令行運行。從無代碼的java代碼調用hadoop作業

但是，如果我嘗試從命令行運行它，但未將類映射器和Reducer類作爲jar添加到類路徑，它會失敗，儘管我將兩個類都添加到類路徑中。我想知道在hadoop中是否存在一些限制，因爲它接受映射器& reducer類作爲普通的類文件。創建一個jar永遠是強制性的？

public class WordCountDriver extends Configured implements Tool {

 public static final String HADOOP_ROOT_DIR = "hdfs://universe:54310/app/hadoop/tmp"; 


static class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> { 

    private Text word = new Text(); 
    private final IntWritable one = new IntWritable(1); 

    public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { 

     String line = value.toString(); 
     StringTokenizer itr = new StringTokenizer(line.toLowerCase()); 
     while (itr.hasMoreTokens()) { 
      word.set(itr.nextToken()); 
      context.write(word, one); 
     } 
    } 
}; 

static class WordCountReducer extends Reducer<Text, IntWritable, Text, IntWritable> { 

    public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { 

     int sum = 0; 

     for (IntWritable value : values) { 
      sum += value.get(); // process value 
     }  
     context.write(key, new IntWritable(sum)); 
    } 
}; 


/** 
* 
*/ 
public int run(String[] args) throws Exception { 

    Configuration conf = getConf(); 

    conf.set("mapred.job.tracker", "universe:54311"); 

    Job job = new Job(conf, "Word Count"); 

    // specify output types 
    job.setOutputKeyClass(Text.class); 
    job.setOutputValueClass(IntWritable.class); 

    // specify input and output dirs 
    FileInputFormat.addInputPath(job, new Path(HADOOP_ROOT_DIR + "/input")); 
    FileOutputFormat.setOutputPath(job, new Path(HADOOP_ROOT_DIR + "/output")); 

    // specify a mapper 
    job.setMapperClass(WordCountDriver.WordCountMapper.class); 

    // specify a reducer 
    job.setReducerClass(WordCountDriver.WordCountReducer.class); 
    job.setCombinerClass(WordCountDriver.WordCountReducer.class); 

    job.setJarByClass(WordCountDriver.WordCountMapper.class); 

    return job.waitForCompletion(true) ? 0 : 1; 
} 

/** 
* 
* @param args 
* @throws Exception 
*/ 
public static void main(String[] args) throws Exception { 
    int res = ToolRunner.run(new Configuration(), new WordCountDriver(), args); 
    System.exit(res); 
}

}

來源

2012-04-02 cosmos