SequenceFileOutputFormat.java 文件源码

protected SequenceFile.Writer getSequenceWriter(TaskAttemptContext context,
    Class<?> keyClass, Class<?> valueClass) 
    throws IOException {
  Configuration conf = context.getConfiguration();

  CompressionCodec codec = null;
  CompressionType compressionType = CompressionType.NONE;
  if (getCompressOutput(context)) {
    // find the kind of compression to do
    compressionType = getOutputCompressionType(context);
    // find the right codec
    Class<?> codecClass = getOutputCompressorClass(context, 
                                                   DefaultCodec.class);
    codec = (CompressionCodec) 
      ReflectionUtils.newInstance(codecClass, conf);
  }
  // get the path of the temporary output file 
  Path file = getDefaultWorkFile(context, "");
  FileSystem fs = file.getFileSystem(conf);
  return SequenceFile.createWriter(fs, conf, file,
           keyClass,
           valueClass,
           compressionType,
           codec,
           context);
}