Hadoop ToolRunner接口使用异常：仍出现GenericOptionsParser警告

我已经实现了ToolRunner接口，但执行Hadoop任务时仍收到WARN [JobClient] Use GenericOptionsParser警告。执行命令如下：

hadoop jar gc.jar stubs.AvgWordLength -D mapred.reduce.tasks=10 myInput.txt myOutput_res

命令可正常运行，但警告无法消除。使用Linux系统，Driver/ToolRunner代码如下：

package stubs;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class AvgWordLength extends Configured implements Tool {

    public static void main(String[] args) throws Exception {

        int exitCode = ToolRunner.run(new Configuration(), new AvgWordLength(), args);
        System.exit(exitCode);

    }

    @Override
    public int run(String[] args) throws Exception {
        /*
         * Validate that two arguments were passed from the command line.
         */
        if (args.length != 2) {
            System.out.printf("Usage: AvgWordLength <input dir> <output dir>\n");
            System.exit(-1);
        }

        /*
         * Instantiate a Job object for your job's configuration.
         */
        Job job = Job.getInstance(getConf());

        /*
         * Specify the jar file that contains your driver, mapper, and reducer.
         * Hadoop will transfer this jar file to nodes in your cluster running
         * mapper and reducer tasks.
         */
        job.setJarByClass(AvgWordLength.class);

        /*
         * Specify an easily-decipherable name for the job. This job name will
         * appear in reports and logs.
         */
        job.setJobName("Average Word Length");

        /*
         * Specify the paths to the input and output data based on the
         * command-line arguments.
         */
        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        /*
         * Specify the mapper and reducer classes.
         */
        job.setMapperClass(LetterMapper.class);
        job.setReducerClass(AverageReducer.class);

        /*
         * The input file and output files are text files, so there is no need
         * to call the setInputFormatClass and setOutputFormatClass methods.
         */

        /*
         * The mapper's output keys and values have different data types than
         * the reducer's output keys and values. Therefore, you must call the
         * setMapOutputKeyClass and setMapOutputValueClass methods.
         */
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);

        /*
         * Specify the job's output key and value classes.
         */
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(DoubleWritable.class);

        /*
         * Start the MapReduce job and wait for it to finish. If it finishes
         * successfully, return 0. If not, return 1.
         */
        boolean success = job.waitForCompletion(true);
        return (success ? 0 : 1);
    }
}

这个警告的核心原因是代码中Configuration的传递方式不符合Hadoop对通用参数解析的预期，尽管你使用了ToolRunner，但手动传入的new Configuration()干扰了参数解析流程，具体修改如下：

1. 调整main方法中的ToolRunner调用
   将main方法中的调用代码从：

int exitCode = ToolRunner.run(new Configuration(), new AvgWordLength(), args);

修改为：

int exitCode = ToolRunner.run(new AvgWordLength(), args);

因为AvgWordLength继承了Configured，ToolRunner会自动为其创建并初始化Configuration，同时自动解析命令行中的通用参数（如-D开头的配置项）到这个Configuration中，无需手动传入新的Configuration实例。

2. 确认配置传递正确性
   run方法中Job.getInstance(getConf())的写法是正确的，getConf()会返回ToolRunner处理过的、已经包含命令行参数的Configuration对象，确保你的reduce任务数等配置能正常生效。

3. 关于警告的额外说明
   如果修改后仍出现该警告，大概率是Hadoop旧版本的兼容性问题——部分早期Hadoop版本即使正确使用ToolRunner，也会弹出这个提示。此时可以忽略警告，只要你的任务能正常运行、配置参数生效（可通过Hadoop Web UI查看任务的reduce数量是否为10）即可。

内容的提问来源于stack exchange，提问作者Bernard Joshua