从 map 中键入密钥中的不匹配:expected org.apache.hadoop.io.Text,收到 org.apache.hadoop.io.LongWritable

2022-09-01 18:12:53

我正在尝试在java中运行map/reducer。以下是我的文件

字数.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));
    }
}

我收到以下错误

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

我认为它无法找到Mapper和reducer类。我已经在main类中编写了代码,它正在获得默认的Mapper和reducer类。


答案 1

在代码中添加以下 2 行:

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

默认情况下,您正在使用发出 LongWritable 键和 Text 值,但您将 Text 作为键发出,IntWritable 作为值发出。你需要把这个告诉名声。TextOutputFormat

呵呵


答案 2

这可能不是你的问题,但我曾经遇到过这个愚蠢的问题。确保你没有混合旧库和新库,即mapred与mapreduce。在地图上注释@Overide并简化方法。如果看到错误,则表示未正确重写这些方法。


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