键入map中的键不匹配：期望org.apache.hadoop.io.Text，收到org.apache.hadoop.io.LongWritable

Question

    package Sort;
    import java.io.IOException;
    import org.apache.hadoop.io.DoubleWritable;
    import org.apache.hadoop.io.LongWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Mapper;
    public class sortmapper extends                  Mapper<LongWritable,Text,Text,DoubleWritable> {
        public void map(Text key, Iterable<DoubleWritable> value, Context                            context) throws IOException, InterruptedException {
            String line = value.toString();
            String subId = line.substring(15, 26);
            Double bytes = Double.parseDouble(line.substring(45, 56));
            if (bytes == null) 
                bytes = 0.0;
            context.write(new Text(subId),new DoubleWritable(bytes));
        }
    }

这是我编写的映射器方法，但我收到了上述错误。

Answer 1

问题在于：

  public class sortmapper extends Mapper<LongWritable,Text,Text,DoubleWritable> {
        public void map(Text key, Iterable<DoubleWritable> value, Context      

<强> Mapper<LongWritable,Text,Text,DoubleWritable>

对于您的映射器，输入键和值为：

LongWritable and Text

输出键和值为：

Text and DoubleWritable

您的map()签名应为：

public void map(LongWritable key, Text value, Context context)