無法將作業設置爲JobConf對象

Question

我寫了一個自定義分區程序，但無法將其設置爲主類中的JobConf對象。

import org.apache.hadoop.io.Text; 
import org.apache.hadoop.mapreduce.Partitioner; 

public class FirstCharTextPartitioner extends Partitioner<Text, Text> { 

    @Override 
    public int getPartition(Text key, Text value, int numReduceTasks) { 
     return (key.toString().charAt(0)) % numReduceTasks; 
    }  
} 

但是當我嘗試將它設置爲JobConf對象，我得到以下錯誤。
在類型JobConf方法setPartitionerClass（類）不適用的參數（類）

public class WordCount { 

    public static class Map extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable> { 
     private final static IntWritable one = new IntWritable(1); 
     private Text word = new Text(); 

     public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException { 
      String line = value.toString(); 
      String[] tokens = line.split("\\s"); 
      for (String token : tokens) { 
       word.set(token); 
       output.collect(word, one); 
      } 
     } 
    } 

    public static class Reduce extends MapReduceBase implements Reducer<Text, IntWritable, Text, IntWritable> { 
     public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException { 
      int sum = 0; 
      while (values.hasNext()) { 
       sum += values.next().get(); 
      } 
      output.collect(key, new IntWritable(sum)); 
     } 
    } 

    public static void main(String[] args) throws Exception { 
     JobConf conf = new JobConf(WordCount.class); 
     conf.setJobName("wordcount"); 

     conf.setOutputKeyClass(Text.class); 
     conf.setOutputValueClass(IntWritable.class); 

     conf.setMapperClass(Map.class); 
     conf.setCombinerClass(Reduce.class); 
     conf.setReducerClass(Reduce.class); 
     conf.setPartitionerClass(FirstCharTextPartitioner.class); 

     conf.setInputFormat(TextInputFormat.class); 
     conf.setOutputFormat(TextOutputFormat.class); 

     FileInputFormat.setInputPaths(conf, new Path(args[0])); 
     FileOutputFormat.setOutputPath(conf, new Path(args[1])); 

     JobClient.runJob(conf); 
    } 
} 

有人能告訴我什麼，我做錯了什麼？

Answer 1

您正在導入新org.apache.hadoop.mapreduce.Partitioner。

您需要實現舊接口org.apache.hadoop.mapred.Partitioner，像這樣：

import org.apache.hadoop.io.Text; 
import org.apache.hadoop.mapred.Partitioner; 

public class FirstCharTextPartitioner implements Partitioner<Text, Text> { 

    @Override 
    public int getPartition(Text key, Text value, int numReduceTasks) { 
     return (key.toString().charAt(0)) % numReduceTasks; 
    }  
}