001/*
002 * Copyright 2002-2015 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.servlet.resource;
018
019import java.io.IOException;
020
021import org.springframework.core.io.Resource;
022import org.springframework.util.DigestUtils;
023import org.springframework.util.FileCopyUtils;
024
025/**
026 * A {@code VersionStrategy} that calculates an Hex MD5 hashes from the content
027 * of the resource and appends it to the file name, e.g.
028 * {@code "styles/main-e36d2e05253c6c7085a91522ce43a0b4.css"}.
029 *
030 * @author Brian Clozel
031 * @author Rossen Stoyanchev
032 * @since 4.1
033 * @see VersionResourceResolver
034 */
035public class ContentVersionStrategy extends AbstractVersionStrategy {
036
037        public ContentVersionStrategy() {
038                super(new FileNameVersionPathStrategy());
039        }
040
041        @Override
042        public String getResourceVersion(Resource resource) {
043                try {
044                        byte[] content = FileCopyUtils.copyToByteArray(resource.getInputStream());
045                        return DigestUtils.md5DigestAsHex(content);
046                }
047                catch (IOException ex) {
048                        throw new IllegalStateException("Failed to calculate hash for " + resource, ex);
049                }
050        }
051
052}