001/*
002 * Copyright 2002-2019 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.http;
018
019import java.io.BufferedReader;
020import java.io.IOException;
021import java.io.InputStream;
022import java.io.InputStreamReader;
023import java.nio.charset.StandardCharsets;
024import java.util.Collections;
025import java.util.List;
026import java.util.Locale;
027import java.util.Optional;
028
029import org.springframework.core.io.Resource;
030import org.springframework.lang.Nullable;
031import org.springframework.util.LinkedMultiValueMap;
032import org.springframework.util.MultiValueMap;
033import org.springframework.util.StringUtils;
034
035/**
036 * A factory delegate for resolving {@link MediaType} objects
037 * from {@link Resource} handles or filenames.
038 *
039 * @author Juergen Hoeller
040 * @author Arjen Poutsma
041 * @since 5.0
042 */
043public final class MediaTypeFactory {
044
045        private static final String MIME_TYPES_FILE_NAME = "/org/springframework/http/mime.types";
046
047        private static final MultiValueMap<String, MediaType> fileExtensionToMediaTypes = parseMimeTypes();
048
049
050        private MediaTypeFactory() {
051        }
052
053
054        /**
055         * Parse the {@code mime.types} file found in the resources. Format is:
056         * <code>
057         * # comments begin with a '#'<br>
058         * # the format is &lt;mime type> &lt;space separated file extensions><br>
059         * # for example:<br>
060         * text/plain    txt text<br>
061         * # this would map file.txt and file.text to<br>
062         * # the mime type "text/plain"<br>
063         * </code>
064         * @return a multi-value map, mapping media types to file extensions.
065         */
066        private static MultiValueMap<String, MediaType> parseMimeTypes() {
067                InputStream is = MediaTypeFactory.class.getResourceAsStream(MIME_TYPES_FILE_NAME);
068                try (BufferedReader reader = new BufferedReader(new InputStreamReader(is, StandardCharsets.US_ASCII))) {
069                        MultiValueMap<String, MediaType> result = new LinkedMultiValueMap<>();
070                        String line;
071                        while ((line = reader.readLine()) != null) {
072                                if (line.isEmpty() || line.charAt(0) == '#') {
073                                        continue;
074                                }
075                                String[] tokens = StringUtils.tokenizeToStringArray(line, " \t\n\r\f");
076                                MediaType mediaType = MediaType.parseMediaType(tokens[0]);
077                                for (int i = 1; i < tokens.length; i++) {
078                                        String fileExtension = tokens[i].toLowerCase(Locale.ENGLISH);
079                                        result.add(fileExtension, mediaType);
080                                }
081                        }
082                        return result;
083                }
084                catch (IOException ex) {
085                        throw new IllegalStateException("Could not load '" + MIME_TYPES_FILE_NAME + "'", ex);
086                }
087        }
088
089        /**
090         * Determine a media type for the given resource, if possible.
091         * @param resource the resource to introspect
092         * @return the corresponding media type, or {@code null} if none found
093         */
094        public static Optional<MediaType> getMediaType(@Nullable Resource resource) {
095                return Optional.ofNullable(resource)
096                                .map(Resource::getFilename)
097                                .flatMap(MediaTypeFactory::getMediaType);
098        }
099
100        /**
101         * Determine a media type for the given file name, if possible.
102         * @param filename the file name plus extension
103         * @return the corresponding media type, or {@code null} if none found
104         */
105        public static Optional<MediaType> getMediaType(@Nullable String filename) {
106                return getMediaTypes(filename).stream().findFirst();
107        }
108
109        /**
110         * Determine the media types for the given file name, if possible.
111         * @param filename the file name plus extension
112         * @return the corresponding media types, or an empty list if none found
113         */
114        public static List<MediaType> getMediaTypes(@Nullable String filename) {
115                return Optional.ofNullable(StringUtils.getFilenameExtension(filename))
116                                .map(s -> s.toLowerCase(Locale.ENGLISH))
117                                .map(fileExtensionToMediaTypes::get)
118                                .orElse(Collections.emptyList());
119        }
120
121}