使用 ArrayWritable 的序列化似乎以一种有趣的方式工作

and this is the test mapper that I was using:

public static class MyMapper extends Mapper<LongWritable, Text, LongWritable, IntArrayWritable> {

    public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        int red = Integer.parseInt(value.toString());
        IntWritable[] a = new IntWritable[100];

        for (int i =0;i<a.length;i++){
            a[i] = new IntWritable(red+i);
        }

        IntArrayWritable aw = new IntArrayWritable();
        aw.set(a);
        context.write(key, aw);
    }
}

IntArrayWritable 取自 javadoc 中给出的示例:ArrayWritable.

import org.apache.hadoop.io.ArrayWritable;
import org.apache.hadoop.io.IntWritable;

public class IntArrayWritable extends ArrayWritable {
    public IntArrayWritable() {
        super(IntWritable.class);
    }
}