package wc; import java.io.IOException; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.util.GenericOptionsParser; public class WordCountMain { public static void main(String[] args) throws Exception{ // TODO Auto-generated method stub Configuration conf = new Configuration(); conf.set("fs.default.name","hdfs://localhost:9000"); String[] otherArgs = new String[]{"input","output"}; /* 直接设置输入参数 */ if (otherArgs.length != 2) { System.err.println("Usage: wordcount <in><out>"); System.exit(2); } Job job = Job.getInstance(conf,"Merge and duplicate removal"); job.setJarByClass(WordCountMapper.class); job.setMapperClass(Map.class); job.setCombinerClass(WordCountReduce.class); job.setReducerClass(WordCountReduce.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(Text.class); FileInputFormat.addInputPath(job, new Path(otherArgs[0])); FileOutputFormat.setOutputPath(job, new Path(otherArgs[1])); System.exit(job.waitForCompletion(true) ? 0 : 1); } } package wc; import java.io.IOException; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.io.Text; public class WordCountMapper{ public static class Map extends Mapper<Object, Text, Text, Text>{ private static Text text = new Text(); public void map(Object key, Text value, Context context) throws IOException,InterruptedException{ text = value; context.write(text, new Text("")); } } } job.setmapperclass出错

在您的代码中，您定义了一个名为 WordCountMapper 的类，该类实际上应该是一个 Mapper 类，并且应该继承 Mapper 接口。但是，在您的代码中，WordCountMapper 类没有继承 Mapper 接口，因此在设置 Mapper 类时出现了错误。

您需要将 WordCountMapper 类修改为一个 Mapper 类，并且让它继承 Mapper 接口，如下所示：

package wc;

import java.io.IOException;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.io.Text;

public class WordCountMapper extends Mapper<Object, Text, Text, Text> {

    private static Text text = new Text();

    public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
        text = value;
        context.write(text, new Text(""));
    }
}

然后，您需要将 `job.setMapperClass(Map.class)` 修改为 `job.setMapperClass(WordCountMapper.class)`，以设置正确的 Mapper 类。