MultipleOutputs.java

/**
   * Write key and value to baseOutputPath using the namedOutput.
   * 
   * @param namedOutput    the named output name
   * @param key            the key
   * @param value          the value
   * @param baseOutputPath base-output path to write the record to.
   * Note: Framework will generate unique filename for the baseOutputPath
   */
  @SuppressWarnings("unchecked")
  public <K, V> void write(String namedOutput, K key, V value,
      String baseOutputPath) throws IOException, InterruptedException {
    checkNamedOutputName(context, namedOutput, false);
    checkBaseOutputPath(baseOutputPath);
    if (!namedOutputs.contains(namedOutput)) {
      throw new IllegalArgumentException("Undefined named output '" +
        namedOutput + "'");
    }
    TaskAttemptContext taskContext = getContext(namedOutput);
    getRecordWriter(taskContext, baseOutputPath).write(key, value);
  }

  /**
   * Write key value to an output file name.
   * 
   * Gets the record writer from job's output format.  
   * Job's output format should be a FileOutputFormat.
   * 
   * @param key       the key
   * @param value     the value
   * @param baseOutputPath base-output path to write the record to.
   * Note: Framework will generate unique filename for the baseOutputPath
   */
  @SuppressWarnings("unchecked")
  public void write(KEYOUT key, VALUEOUT value, String baseOutputPath) 
      throws IOException, InterruptedException {
    checkBaseOutputPath(baseOutputPath);
    TaskAttemptContext taskContext = new TaskAttemptContext(
      context.getConfiguration(), context.getTaskAttemptID());
    getRecordWriter(taskContext, baseOutputPath).write(key, value);
  }