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

Question

我有两个映射器类。所以使用ChainMapper.addMapper方法添加Mapper，使用ChainReducer.setReducer方法设置Reducer。 ChainMapper.addMapper 方法正常 但是 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)

这是我的驱动程序类:

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;
    }

还尝试通过删除 boolean 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

终于找到解决办法了。 导入了错误的包，即。 导入 org.apache.hadoop.mapreduce.lib.chain.ChainReducer;而不是 import org.apache.hadoop.mapred.lib.ChainReducer;