我有一个HBase MapReduce Bulkload应用程序，其中包括一个自定义的MyMapper类，它有一个静态字段parser，在应用程序运行期间使用。当我配置作业时，我使用config方法初始化静态字段parser。
但是当作业运行时，带注解的行抛出一个空指针异常，看起来像是在将作业提交给Yarn之后，静态字段parser变为空。
这是Map器的代码，Hadoop的版本是2.7.7.

public class MyMapper extends Mapper<LongWritable, Text, ImmutableBytesWritable, Put> {

  private static StringParser parser;

  public static void config(StringParser parser) {
    MyMapper.parser = parser;
  }

  @Override
  protected void map(LongWritable key, Text value, Context context)
      throws IOException, InterruptedException {
    String lineValue = value.toString();
    String output;
    try {
      // null pointer exception this line.
      output = parser.parse(lineValue); 
      context.write(new ImmutableBytesWritable(..., ...);
    } catch (ParseException e) {
      e.printStackTrace();
    }
  }
}

下面是有关作业提交的代码：

Job job = Job.getInstance(conf, "Batch Import HBase Table：" + tableName);
    job.setJarByClass(TextBulkLoadDriver.class);
    FileInputFormat.setInputPaths(job, inPath);

    // Config Mapper related content, here I set the static field in MyMapper class.
    MyMapper.config(parser); 
    Class<MyMapper> cls = MyMapper.class;
    job.setMapperClass(cls);
    job.setMapOutputKeyClass(ImmutableBytesWritable.class);
    job.setMapOutputValueClass(Put.class);

    job.setNumReduceTasks(1);
    job.setReducerClass(PutSortReducer.class);

    RegionLocator locator = instance.getConnection().getRegionLocator(TableName.valueOf(tableName));
    try (Admin admin = instance.getAdmin(); Table table = instance.getTable(tableName)) {
      HFileOutputFormat2.configureIncrementalLoad(job, table, locator);
      HFileOutputFormat2.setOutputPath(job, outPath);
      // run the job
      job.waitForCompletion(true);
      logger.info("HFileOutputFormat2 file ready on {}", outPath);
      LoadIncrementalHFiles loader = new LoadIncrementalHFiles(conf);
      loader.doBulkLoad(outPath, admin, table, locator);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }

TIA为所有建议！