seojangho commented on a change in pull request #48: [NEMO-72] Instance-based Encoder/Decoder interface URL: https://github.com/apache/incubator-nemo/pull/48#discussion_r196290220
########## File path: common/src/main/java/edu/snu/nemo/common/coder/EncoderFactory.java ########## @@ -0,0 +1,90 @@ +/* + * Copyright (C) 2018 Seoul National University + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package edu.snu.nemo.common.coder; + +import java.io.IOException; +import java.io.OutputStream; +import java.io.Serializable; + +/** + * A encoder factory object which generates encoders that encode values of type {@code T} into byte streams. + * To avoid to generate instance-based coder such as Spark serializer for every encoding, + * user need to explicitly instantiate an encoder instance and use it. + * + * @param <T> element type. + */ +public interface EncoderFactory<T> extends Serializable { + + /** + * Get an encoder instance. + * + * @param outputStream the stream on which encoded bytes are written + * @return the encoder instance. + * @throws IOException if fail to get the instance. + */ + Encoder<T> create(OutputStream outputStream) throws IOException; + + /** + * Interface of Encoder. + * + * @param <T> element type. + */ + interface Encoder<T> { + + /** + * Encodes the given value onto the specified output stream. + * It have to be able to encode the given stream consequently by calling this method repeatedly. + * Because the user can want to keep a single output stream and continuously concatenate elements, + * the output stream should not be closed. + * + * @param element the element to be encoded + * @throws IOException if fail to encode + */ + void encode(T element) throws IOException; + } + + /** + * Dummy encoder factory. + */ + EncoderFactory DUMMY_ENCODER_FACTORY = new DummyEncoderFactory(); + + /** + * Dummy encoder factory implementation which is not supposed to be used. + */ + final class DummyEncoderFactory implements EncoderFactory { + + /** + * DummyEncoder. + */ + private final class DummyEncoder implements Encoder { + + @Override + public void encode(final Object element) { + throw new RuntimeException("DummyEncoder is not supposed to be used."); + } + } + + @Override + public Encoder create(final OutputStream outputStream) { + return new DummyEncoder(); Review comment: return DUMMY_ENCODER ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
