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_r196290166
########## File path: common/src/main/java/edu/snu/nemo/common/coder/DecoderFactory.java ########## @@ -0,0 +1,89 @@ +/* + * 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.InputStream; +import java.io.Serializable; + +/** + * A decoder factory object which generates decoders that decode values of type {@code T} into byte streams. + * To avoid to generate instance-based coder such as Spark serializer for every decoding, + * user need to instantiate a decoder instance and use it. + * + * @param <T> element type. + */ +public interface DecoderFactory<T> extends Serializable { + + /** + * Get a decoder instance. + * + * @param inputStream the input stream to decode. + * @return the decoder instance. + * @throws IOException if fail to get the instance. + */ + Decoder<T> create(InputStream inputStream) throws IOException; + + /** + * Interface of Decoder. + * + * @param <T> element type. + */ + interface Decoder<T> { + + /** + * Decodes the a value from the given input stream. + * It have to be able to decode the given stream consequently by calling this method repeatedly. + * Because there are many elements in the input stream, the stream should not be closed. + * + * @return the decoded element + * @throws IOException if fail to decode + */ + T decode() throws IOException; + } + + /** + * Dummy coder factory. + */ + DecoderFactory DUMMY_DECODER_FACTORY = new DummyDecoderFactory(); + + /** + * Dummy coder factory implementation which is not supposed to be used. + */ + final class DummyDecoderFactory implements DecoderFactory { + + /** + * DummyDecoder. + */ + private final class DummyDecoder implements Decoder { + + @Override + public Object decode() { + throw new RuntimeException("DummyDecoder is not supposed to be used."); + } + } + + @Override + public Decoder create(final InputStream inputStream) { + return new DummyDecoder(); Review comment: return DUMMY_DECODER ---------------------------------------------------------------- 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
