25

I am trying to run a map/reducer in java. Below are my files

WordCount.java

package counter;


public class WordCount extends Configured implements Tool {

public int run(String[] arg0) throws Exception {
    Configuration conf = new Configuration();

    Job job = new Job(conf, "wordcount");

    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);

    job.setMapperClass(WordCountMapper.class);
    job.setReducerClass(WordCountReducer.class);

    job.setInputFormatClass(TextInputFormat.class);
    job.setOutputFormatClass(TextOutputFormat.class);

    FileInputFormat.addInputPath(job, new Path("counterinput"));
    // Erase previous run output (if any)
    FileSystem.get(conf).delete(new Path("counteroutput"), true);
    FileOutputFormat.setOutputPath(job, new Path("counteroutput"));

    job.waitForCompletion(true);
    return 0;
}   

public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(new Configuration(), new WordCount(), args);
    System.exit(res);

    }
}

WordCountMapper.java

public class WordCountMapper extends
Mapper<LongWritable, Text, Text, IntWritable> {
    private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();

    public void map(LongWritable key, Text value, OutputCollector<Text,IntWritable> output, Reporter reporter)
    throws IOException, InterruptedException {
        System.out.println("hi");
    String line = value.toString();
    StringTokenizer tokenizer = new StringTokenizer(line);
    while (tokenizer.hasMoreTokens()) {
        word.set(tokenizer.nextToken());
        output.collect(word, one);
        }
    }
}

WordCountReducer.java

public class WordCountReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
    public void reduce(Text key, Iterator<IntWritable> values,
        OutputCollector<Text,IntWritable> output, Reporter reporter) throws IOException, InterruptedException {
        System.out.println("hello");
        int sum = 0;
        while (values.hasNext()) {
            sum += values.next().get();
        }
        output.collect(key, new IntWritable(sum));
    }
}

I am getting following error

13/06/23 23:13:25 INFO jvm.JvmMetrics: Initializing JVM Metrics with  
processName=JobTracker, sessionId=

13/06/23 23:13:25 WARN mapred.JobClient: Use GenericOptionsParser for parsing the 
arguments. Applications should implement Tool for the same.
13/06/23 23:13:26 INFO input.FileInputFormat: Total input paths to process : 1
13/06/23 23:13:26 INFO mapred.JobClient: Running job: job_local_0001
13/06/23 23:13:26 INFO input.FileInputFormat: Total input paths to process : 1
13/06/23 23:13:26 INFO mapred.MapTask: io.sort.mb = 100
13/06/23 23:13:26 INFO mapred.MapTask: data buffer = 79691776/99614720
13/06/23 23:13:26 INFO mapred.MapTask: record buffer = 262144/327680
13/06/23 23:13:26 WARN mapred.LocalJobRunner: job_local_0001
java.io.IOException: Type mismatch in key from map: expected org.apache.hadoop.io.Text, 
recieved org.apache.hadoop.io.LongWritable
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:845)
at org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:541)
at org.
apache.hadoop.mapreduce.TaskInputOutputContext.write(TaskInputOutputContext.java:80)
at org.apache.hadoop.mapreduce.Mapper.map(Mapper.java:124)
at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:621)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:177)
13/06/23 23:13:27 INFO mapred.JobClient:  map 0% reduce 0%
13/06/23 23:13:27 INFO mapred.JobClient: Job complete: job_local_0001
13/06/23 23:13:27 INFO mapred.JobClient: Counters: 0

I think it is not able to find Mapper and reducer class. I have written the code in main class, It is getting default Mapper and reducer class.

4

4 回答 4

49

在您的代码中添加这两行：

job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);

您正在使用TextOutputFormat默认情况下发出 LongWritable 键和 Text 值，但您将 Text 作为键和 IntWritable 作为值发出。你需要把这件事告诉成名。

高温高压

于 2013-06-23T16:19:39.003 回答
7

这可能不是你的问题，但我曾经遇到过这个愚蠢的问题。确保您没有混合旧库和新库，即 mapred 与 mapreduce。在您的地图上注释 @Overide 并减少方法。如果您看到错误，则说明您没有正确覆盖这些方法。

于 2013-12-30T22:25:44.440 回答
7

由于在我的代码中设置了不正确的 Mapper 类，我得到了类似的异常堆栈跟踪（错字:)）

job.setMapperClass(Mapper.class)  // Set to org.apache.hadoop.mapreduce.Mapper due to type

请注意，我错误地使用了 mapreduce 包中的 Mapper 类，我将其更改为我的自定义映射器类：

job.setMapperClass(LogProcMapperClass.class) // LogProcMapperClass is my custom mapper.

在我更正了映射器类后，异常得到了解决。

于 2014-07-21T12:18:02.920 回答
2

从代码中删除它解决了这个问题

super.map(key, value, context);
于 2018-04-18T14:37:50.993 回答