斯卡拉 MapReduce : [error] method reduce overrides nothing

Question

我遇到了这个错误，我这样写了我的 TableReducer 代码:

class treducer extends TableReducer[Text, IntWritable, ImmutableBytesWritable]{
    override def reduce(key: Text, values: java.lang.Iterable[IntWritable], context:Reducer[Text, IntWritable, ImmutableBytesWritable, Mutation]#Context){
        var i=0
        for (v <- values) {
          i += v.get()
        }
        val put = new Put(Bytes.toBytes(key.toString()))  // be sure to comment on toString.getBytes
        put.add(Families.cf.bytes , Qualifiers.count.bytes, Bytes.toBytes(i))

        context.write(null, put)
    }
}

通过这次导入:

import org.apache.hadoop.hbase.HBaseConfiguration
import org.apache.hadoop.hbase.client.HBaseAdmin
import org.apache.hadoop.hbase.client.HTable
import org.apache.hadoop.hbase.util.Bytes
import org.apache.hadoop.hbase.client.Put
import org.apache.hadoop.hbase.client.Get
import java.io.IOException
import org.apache.hadoop.conf.Configuration
import org.apache.hadoop.hbase._
import org.apache.hadoop.hbase.client._
import org.apache.hadoop.hbase.io._
import org.apache.hadoop.hbase.mapreduce._
import org.apache.hadoop.io._
import scala.collection.JavaConversions._
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat
import org.apache.hadoop.mapreduce.Job
import org.apache.hadoop.mapreduce.Mapper
import org.apache.hadoop.mapreduce.ReduceContext
import org.apache.hadoop.mapreduce.Reducer

但是出现了这个错误:

[error] /home/ans4175/activator/scala-hbase/src/main/scala/com/example/Hello.scala:85: method reduce overrides nothing.
[error] Note: the super classes of class treducer contain the following, non final members named reduce:
[error] protected[package mapreduce] def reduce(x$1: org.apache.hadoop.io.Text,x$2: Iterable[org.apache.hadoop.io.IntWritable],x$3: org.apache.hadoop.mapreduce.Reducer[org.apache.hadoop.io.Text,org.apache.hadoop.io.IntWritable,org.apache.hadoop.hbase.io.ImmutableBytesWritable,org.apache.hadoop.io.Writable]#Context): Unit
[error]     override def reduce(key: Text, values: java.lang.Iterable[IntWritable], context:Reducer[Text, IntWritable, ImmutableBytesWritable, Mutation]#Context){
[error]                  ^
[error] one error found
[error] (compile:compile) Compilation failed

我不知道是什么问题。我已经关注了这个帖子 https://github.com/rawg/scala-hbase-wordcount/blob/master/src/main/scala/WordCountReducer.scala , https://github.com/vadimbobrov/calc/blob/master/src/main/scala/com/os/job/InterpolatorReducer.scala

提前致谢

Answer 1

错误提供了您的答案。您错误地声明了其中一个参数。

编译器指出第三个参数的类型是:

Reducer[Text,IntWritable,ImmutableBytesWritable,Writable]#Context

您的重写声明了一个带有此类型第三个参数的方法:

Reducer[Text, IntWritable, ImmutableBytesWritable, Mutation]#Context

将 Mutation 更改为 Writable 将允许编译器覆盖正确的方法。