Question

我有一个实施genkey和writable的课程comparable。我需要将此类的对象从mapper传递给reducer。映射器工作得很好。现在，当我最终尝试通过context.write获得输出时，我得到以下错误......

class org.apache.hadoop.io.Text is not class genkey

这是我的代码

public static class Mappertwo extends Mapper<Object, Text, genkey, IntWritable> {
    private genkey ky=new genkey();
    public void map(Object key , Text value , Context context)
        throws IOException , InterruptedException{

        .............

        context.write(ky,one);
    }          
}
public static class Reducertwo extends Reducer<genkey, IntWritable, Text, IntWritable>
{              
     public void reduce(genkey ukey , Iterable<IntWritable> values , Context context)
        throws IOException , InterruptedException{          

        IntWritable result = new IntWritable();
        Text nw=new Text();
        int sum=0;

        for (IntWritable val : values){
            sum += val.get();
        }

        String s=ukey.getkey();
        nw.set(s);
        result.set(sum);
        context.write(nw,result);
        //this line here gives the error...                        }
}

public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException{
    if (args.length != 5) {
        System.err.println("exceeded array limit:");
        System.exit(-1);
    }

     Configuration conf1 = new Configuration();
     Job job1= new Job(conf1, "round2");
     conf1.set("t",args[2]);
     DistributedCache.addCacheFile(new Path("/user/hduser/out/part-r-00000").toUri(),job1.getConfiguration());
     job1.setJarByClass(MapSide.class);
     job1.setMapperClass(Mappertwo.class);
     job1.setCombinerClass(Reducertwo.class);
     job1.setReducerClass(Reducertwo.class);
     job1.setOutputKeyClass(Text.class);
     job1.setOutputValueClass(IntWritable.class);
     job1.setMapOutputKeyClass(genkey.class);
     FileInputFormat.addInputPath(job1, new Path(args[0]));
     FileOutputFormat.setOutputPath(job1, new Path(args[3]));
     System.exit(job1.waitForCompletion(true)?0:1);
}

Answer 1

您已定义要编写Text, IntWritable。如果你想写genkey, IntWritable，你的reducer定义必须如下所示：

public static class Reducertwo extends Reducer<genkey, IntWritable, genkey, IntWritable>

在同一页面上，您的作业输出键类也需要设置为：

 job1.setOutputKeyClass(genkey.class);

自定义可写的错误可比较

1 个答案: