java - 使用自定义 WritableComparable 时出错

Question

我正在尝试实现自定义 WritableComparable，如图所示 In this link

当我尝试在我的映射器方法中初始化自定义可写比较类时出现错误。我已经在我的代码中显示了我的错误。textpair 类应该放在单独的文件中吗？

public class Myprog {
    public static class MyMap extends Mapper<Object, Text, TextPair, IntWritable> {
        public void map(Object key, Text value, Context context)
            throws IOException, InterruptedException {
            TextPair writable = new TextPair();

           //ERROR in this line 
           //No enclosing instance of type Myprog is accessible. Must qualify 
           //the allocation with an enclosing instance of type Myprog 
           //(e.g. x.new A() where x is an instance of Myprog).
            ....
    }
}

public static class MyReduce extends Reducer<TextPair, IntWritable, Text, Text> {
    public void reduce(TextPair key, Iterable<IntWritable> values, Context context)
        throws IOException, InterruptedException {
    }
}

public class TextPair implements WritableComparable<TextPair> {
      ....
}

public static void main(String[] args) throws Exception {
    Configuration conf = new Configuration();
    String[] otherArgs = 
        new GenericOptionsParser(conf, args).getRemainingArgs();
    Collections.addAll(headerList, header.split(","));
    Job job = new Job(conf, "Myprog");
    job.setJarByClass(Myprog.class);
    job.setMapperClass(MyMap.class);
    job.setReducerClass(MyReduce.class);
    job.setMapOutputKeyClass(TextPair.class); 
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(Text.class);

    FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
    FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));

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

Answer 1

您必须将TextPair 定义为static。没有 Myprog 的外部实例就无法实例化。由于您的 Mapper 是静态的，因此它没有要引用的 Myprog 实例。

使用

public static class TextPair 

将解决您的问题。