Question

我搜索过这个问题的解决方案无济于事。我有三个scala类：MaxTemperatureMapper，MaxTemperatureReducer和MaxTemperatureDriver（请参阅下面的实现）。之前线程中的某些人删除了Main类（job.setJar()）中的MaxTemperatureDriver方法，以使hadoop作业运行。这对我不起作用。运行时，我继续收到以下stacktrace：

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

我正在使用intellij IDE并使用maven进行依赖，编译等。我在命令行上运行前面提到的hadoop命令。有人可以解释我哪里出错吗？为什么没有找到Mapper类？

MaxTemperatureMapper：

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)) )
  }

}

MaxTemperatureDriver：

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)

  }
}

Answer 1

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

使用以下命令添加（例如）current和lib目录中的所有jar依赖项：

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

请记住，通过hadoop jar开始工作时，您还需要使用-libjars将任何依赖项的jar传递给它。我喜欢用：

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

注意： sed命令需要不同的分隔符; HADOOP_CLASSPATH已:分开且-libjars需要,分开。

Hadoop作业在java.lang.ClassNotFoundException上失败

1 个答案: