ChainReducer.setReducer 方法抛出错误"ChainReducer is not applicable for the arguments"

Question

我有两个映射器类。因此使用ChainMapper.addMapper方法添加Mapper，使用ChainReducer.setReducer方法设置Reducer。ChainMapper.addMapper方法可以，但Chain.setReducer方法抛出语法错误

The method setReducer(Job, Class<? extends Reducer>, Class<?>, Class<?>, Class<?>, Class<?>, Configuration) in the type ChainReducer is not applicable for the arguments (JobConf, Class<FileComparisionReduce>, Class<LongWritable>, Class<Text>, Class<LongWritable>, Class<Text>, boolean, JobConf)

这是我的驾驶员课程：

package fileComparision;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.lib.ChainMapper;
import org.apache.hadoop.mapreduce.lib.chain.ChainReducer;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
public class DriverComparision extends Configured implements Tool{

    @Override
    public int run(String[] arg0) throws Exception {
        JobConf conf = new JobConf(true);
        conf.setJobName("Comaprision of 2 file ");
        JobConf Mapper1 = new JobConf(false);

        ChainMapper.addMapper(conf, FileComparisionMapper1.class, LongWritable.class, Text.class, LongWritable.class, Text.class, true, Mapper1);
        JobConf Mapper2 = new JobConf(false);
        ChainMapper.addMapper(conf, FileComparisionMapper2.class, LongWritable.class, Text.class, LongWritable.class, Text.class, true, Mapper2);

    JobConf Reduc = new JobConf(false);
        ChainReducer.setReducer(conf, FileComparisionReduce.class, LongWritable.class, Text.class, LongWritable.class, Text.class, true , Reduc);

        FileInputFormat.setInputPaths(conf, new Path(arg0[0]));
        FileOutputFormat.setOutputPath(conf, new Path(arg0[1]));
        conf.setMapOutputKeyClass(LongWritable.class);
        conf.setMapOutputValueClass(Text.class);
        conf.setOutputKeyClass(LongWritable.class);
        conf.setOutputValueClass(Text.class);

        JobClient.runJob(conf);
        return 0;
    }

还尝试删除布尔参数"true"

JobConf Reduc = new JobConf(false);
        ChainReducer.setReducer(conf, FileComparisionReduce.class, LongWritable.class, Text.class, LongWritable.class, Text.class, true , Reduc);

Answer 1

最后，我得到了一个解决方案。导入错误的包，即import org.apache.hadoop.mapreduce.lib.chain.ChainReducer；而不是import org.apache.hadoop.mapred.lib.ChainReducer;