SequenceFile.java 文件源码

/**
 * Construct the preferred type of 'raw' SequenceFile Writer.
 * @param conf The configuration.
 * @param out The stream on top which the writer is to be constructed.
 * @param keyClass The 'key' type.
 * @param valClass The 'value' type.
 * @param compressionType The compression type.
 * @param codec The compression codec.
 * @param metadata The metadata of the file.
 * @return Returns the handle to the constructed SequenceFile Writer.
 * @throws IOException
 */
public static Writer
  createWriter(Configuration conf, FSDataOutputStream out, 
               Class keyClass, Class valClass, CompressionType compressionType,
               CompressionCodec codec, Metadata metadata)
  throws IOException {
  if ((codec instanceof GzipCodec) && 
      !NativeCodeLoader.isNativeCodeLoaded() && 
      !ZlibFactory.isNativeZlibLoaded(conf)) {
    throw new IllegalArgumentException("SequenceFile doesn't work with " +
                                       "GzipCodec without native-hadoop code!");
  }

  Writer writer = null;

  if (compressionType == CompressionType.NONE) {
    writer = new Writer(conf, out, keyClass, valClass, metadata);
  } else if (compressionType == CompressionType.RECORD) {
    writer = new RecordCompressWriter(conf, out, keyClass, valClass, codec, metadata);
  } else if (compressionType == CompressionType.BLOCK){
    writer = new BlockCompressWriter(conf, out, keyClass, valClass, codec, metadata);
  }

  return writer;
}