hadoop - 将 MapWritable 转换为 Hadoop 中的字符串

Question

当我使用 toString() 方法运行我的输出时，我得到:

#zombie org.apache.hadoop.io.MapWritable@b779f586
#zombies        org.apache.hadoop.io.MapWritable@c8008ef9
#zona   org.apache.hadoop.io.MapWritable@99e061a1
#zoology        org.apache.hadoop.io.MapWritable@9d0060be
#zzp    org.apache.hadoop.io.MapWritable@3e52c108

这是我的 reducer 代码，我怎样才能让 map 值打印出来？

package sample;

import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.MapWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.Reducer;

public class IntSumReducer 
extends Reducer<Text,MapWritable,Text,MapWritable> {
private MapWritable result = new MapWritable();
String temp = "";
public void reduce(Text key, Iterable<MapWritable> values, Context context)throws IOException, InterruptedException {
    result.clear();
    for (MapWritable val : values) {
        Iterable<Writable> keys = val.keySet();
        for (Writable k : keys) {
            IntWritable tally = (IntWritable) val.get(k);
            if (result.containsKey(k)) {
                IntWritable tallies = (IntWritable) result.get(k);
                tallies.set(tallies.get() + tally.get());
                temp = toString() + " : " + tallies.get();
                result.put(new Text(temp), tallies);
            } else {
                temp = k.toString() + " : " + tally.get();
                result.put(new Text(temp), tally);
            }
         }
    }
    context.write(key, result);
}
}

感谢帮助

Answer 1

添加这样的类应该可行:

class MyMapWritable extends MapWritable {
    @Override
    public String toString() {
        StringBuilder result = new StringBuilder();
        Set<Writable> keySet = this.keySet();

        for (Object key : keySet) {
            result.append("{" + key.toString() + " = " + this.get(key) + "}");
        }
        return result.toString();
    }
}

然后这样调用:

MyMapWritable mw = new MyMapWritable();
mw.toString();