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我一直在寻找解决此问题的方法，但无济于事。我有三个 scala 类：MaxTemperatureMapper、MaxTemperatureReducer和MaxTemperatureDriver（参见下面的实现）。之前线程中的一些人删除了job.setJar()Main class( MaxTemperatureDriver) 中的方法以使 hadoop 作业运行。那对我不起作用。运行时，我继续收到以下堆栈跟踪：

  1. hadoop com.koadr.hadoop.MaxTemperatureDriver micro/sample.txt output

  2. hadoop jar target/classes/koadr-hadoop-1.0-SNAPSHOT.jar com.koadr.hadoop.MaxTemperatureDriver micro/sample.txt output：

.

java.lang.RuntimeException: java.lang.ClassNotFoundException: Class com.koadr.hadoop.MaxTemperatureMapper not found
at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:1587)
at org.apache.hadoop.mapreduce.task.JobContextImpl.getMapperClass(JobContextImpl.java:191)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:631)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:330)
at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1408)
at org.apache.hadoop.mapred.Child.main(Child.java:262)
Caused by: java.lang.ClassNotFoundException: Class com.koadr.hadoop.MaxTemperatureMapper not found
at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:1493)
at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:1585)
... 8 more

我在 intellij IDE 中工作，并使用 maven 进行依赖、编译等。我在命令行上运行上述 hadoop 命令。有人可以解释我哪里出错了吗？为什么找不到 Mapper 类？

最大温度映射器：

class MaxTemperatureMapper extends Mapper[Object, Text, Text, IntWritable] {

  private def missing( temp : String) : Boolean = {
    temp.equals("+9999")
  }

 override def map(key: Object, value: Text, context:Mapper[Object,Text,Text,IntWritable]#Context ) = {
    val line : String = value.toString
    val year : String = line.substring(15, 19)
    val temp : String = line.substring(87,92)


    if (!missing(temp)) {
        val airTemp : Int = Integer.parseInt(line.substring(87,92))
        context.write(new Text(year), new IntWritable(airTemp))
    }
  }
}

MaxTemperatureReducer：

class MaxTemperatureReducer extends Reducer[Text, IntWritable, Text, IntWritable] {

  override
  def reduce (key: Text, values: java.lang.Iterable[IntWritable], context:Reducer[Text, IntWritable, Text, IntWritable]#Context) = {
    def maxVal(values : List[IntWritable], cMaxV : Int) : Int = {
      if (values.isEmpty) cMaxV
      else maxVal(values.tail,math.max(cMaxV, values.head.get()))
    }
    context write(new Text(key), new IntWritable(maxVal(values.toList,Integer.MIN_VALUE)) )
  }

}

最高温度驱动程序：

class MaxTemperatureDriver extends Configured with Tool {
  override
  def run(args : Array[String]) : Int = {
    if (args.length != 2) {
      System.err.printf("Usage: %s [generic options] <input> <output>\n", getClass.getSimpleName)
      ToolRunner.printGenericCommandUsage(System.err)
     -1
    }
   val job : Job = Job.getInstance(getConf, "Max Temperature")
   job.setJarByClass(getClass)

   FileInputFormat.addInputPath(job, new Path(args(0)))
   FileOutputFormat.setOutputPath(job, new Path(args(1)))

   job.setMapperClass(classOf[MaxTemperatureMapper])
   job.setCombinerClass(classOf[MaxTemperatureReducer])
   job.setReducerClass(classOf[MaxTemperatureReducer])

   job.setOutputKeyClass(classOf[Text])
   job.setOutputValueClass(classOf[IntWritable])

   if (job.waitForCompletion(true))  0 else 1

   }


 }

object MaxTemperatureDriver {
  def main(args : Array[String]) = {
  val exitCode : Int = ToolRunner.run(new MaxTemperatureDriver, args)
  System.exit(exitCode)

  }
}
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1 回答 1

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您需要在提交作业时添加任何依赖项，HADOOP_CLASSPATH如下-libjars例所示：

使用以下命令从（例如）当前目录和lib目录添加所有 jar 依赖项：

export HADOOP_CLASSPATH=$HADOOP_CLASSPATH:`echo *.jar`:`echo lib/*.jar | sed 's/ /:/g'`

请记住，当您开始工作时，hadoop jar您还需要通过使用-libjars. 我喜欢使用：

hadoop jar <jar> <class> -libjars `echo ./lib/*.jar | sed 's/ /,/g'` [args...]

注意：命令sed需要不同的分隔符；是分开的，HADOOP_CLASSPATH需要分开的。:-libjars,

于 2013-06-13T11:01:03.077 回答