001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.reactive.resource;
018
019import reactor.core.publisher.Flux;
020import reactor.core.publisher.Mono;
021
022import org.springframework.core.io.Resource;
023import org.springframework.core.io.buffer.DataBuffer;
024import org.springframework.core.io.buffer.DataBufferFactory;
025import org.springframework.core.io.buffer.DataBufferUtils;
026import org.springframework.core.io.buffer.DefaultDataBufferFactory;
027import org.springframework.util.DigestUtils;
028import org.springframework.util.StreamUtils;
029
030/**
031 * A {@code VersionStrategy} that calculates an Hex MD5 hashes from the content
032 * of the resource and appends it to the file name, e.g.
033 * {@code "styles/main-e36d2e05253c6c7085a91522ce43a0b4.css"}.
034 *
035 * @author Rossen Stoyanchev
036 * @author Brian Clozel
037 * @since 5.0
038 * @see VersionResourceResolver
039 */
040public class ContentVersionStrategy extends AbstractFileNameVersionStrategy {
041
042        private static final DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory();
043
044
045        @Override
046        public Mono<String> getResourceVersion(Resource resource) {
047                Flux<DataBuffer> flux =
048                                DataBufferUtils.read(resource, dataBufferFactory, StreamUtils.BUFFER_SIZE);
049                return DataBufferUtils.join(flux)
050                                .map(buffer -> {
051                                        byte[] result = new byte[buffer.readableByteCount()];
052                                        buffer.read(result);
053                                        DataBufferUtils.release(buffer);
054                                        return DigestUtils.md5DigestAsHex(result);
055                                });
056        }
057
058}