MapReduce示例代码

  1. /*
  2.  * DEMO Map/Reduce class test2
  3.  * -- Convert GPDBFormat back to TEXT
  4.  */
  5. public static class Map_test2 extends Mapper<LongWritable, GPDBWritable,
  6.   Text, NullWritable> { 
  7.   public void map(LongWritable key, GPDBWritable value, Context context )
  8.     throws IOException {
  9.     try {
  10.       context.write(new Text(value.toString()), NullWritable.get());
  11.     } catch (Exception e) { throw new IOException (e.getMessage()); }
  12.   }
  13. }
  15. public static void runTest2() throws Exception{
  16. Configuration conf = new Configuration(true);
  17.  Job job = new Job(conf, "test2");
  18.  job.setJarByClass(demoMR.class);
  19.  job.setInputFormatClass(GPDBInputFormat.class);
  20.  job.setOutputKeyLClass (Text.class);
  21.  job.setOutputValueClass(NullWritable.class);
  22.  job.setOutputFormatClass(TextOutputFormat.class);
  23.  job.setMapperClass(Map_test2.class);
  24.      GPDBInputFormat.setInputPaths (job, 
  25.      new Path("/demo/data/writeFromGPDB_42"));
  26.  GPDBOutputFormat.setOutputPath(job, new Path("/demo/data/MRTest2"));
  27.  job.waitForCompletion(true);
  29. }

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