spring MediaTypeFactory 源码

spring MediaTypeFactory 代码

文件路径：/spring-web/src/main/java/org/springframework/http/MediaTypeFactory.java

/*
 * Copyright 2002-2021 the original author or authors.
 *
 * 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
 *
 *      https://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 org.springframework.http;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Optional;

import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;

/**
 * A factory delegate for resolving {@link MediaType} objects
 * from {@link Resource} handles or filenames.
 *
 * @author Juergen Hoeller
 * @author Arjen Poutsma
 * @since 5.0
 */
public final class MediaTypeFactory {

	private static final String MIME_TYPES_FILE_NAME = "/org/springframework/http/mime.types";

	private static final MultiValueMap<String, MediaType> fileExtensionToMediaTypes = parseMimeTypes();


	private MediaTypeFactory() {
	}


	/**
	 * Parse the {@code mime.types} file found in the resources. Format is:
	 * <code>
	 * # comments begin with a '#'<br>
	 * # the format is &lt;mime type> &lt;space separated file extensions><br>
	 * # for example:<br>
	 * text/plain    txt text<br>
	 * # this would map file.txt and file.text to<br>
	 * # the mime type "text/plain"<br>
	 * </code>
	 * @return a multi-value map, mapping media types to file extensions.
	 */
	private static MultiValueMap<String, MediaType> parseMimeTypes() {
		InputStream is = MediaTypeFactory.class.getResourceAsStream(MIME_TYPES_FILE_NAME);
		Assert.state(is != null, MIME_TYPES_FILE_NAME + " not found in classpath");
		try (BufferedReader reader = new BufferedReader(new InputStreamReader(is, StandardCharsets.US_ASCII))) {
			MultiValueMap<String, MediaType> result = new LinkedMultiValueMap<>();
			String line;
			while ((line = reader.readLine()) != null) {
				if (line.isEmpty() || line.charAt(0) == '#') {
					continue;
				}
				String[] tokens = StringUtils.tokenizeToStringArray(line, " \t\n\r\f");
				MediaType mediaType = MediaType.parseMediaType(tokens[0]);
				for (int i = 1; i < tokens.length; i++) {
					String fileExtension = tokens[i].toLowerCase(Locale.ENGLISH);
					result.add(fileExtension, mediaType);
				}
			}
			return result;
		}
		catch (IOException ex) {
			throw new IllegalStateException("Could not read " + MIME_TYPES_FILE_NAME, ex);
		}
	}

	/**
	 * Determine a media type for the given resource, if possible.
	 * @param resource the resource to introspect
	 * @return the corresponding media type, or {@code null} if none found
	 */
	public static Optional<MediaType> getMediaType(@Nullable Resource resource) {
		return Optional.ofNullable(resource)
				.map(Resource::getFilename)
				.flatMap(MediaTypeFactory::getMediaType);
	}

	/**
	 * Determine a media type for the given file name, if possible.
	 * @param filename the file name plus extension
	 * @return the corresponding media type, or {@code null} if none found
	 */
	public static Optional<MediaType> getMediaType(@Nullable String filename) {
		return getMediaTypes(filename).stream().findFirst();
	}

	/**
	 * Determine the media types for the given file name, if possible.
	 * @param filename the file name plus extension
	 * @return the corresponding media types, or an empty list if none found
	 */
	public static List<MediaType> getMediaTypes(@Nullable String filename) {
		List<MediaType> mediaTypes = null;
		String ext = StringUtils.getFilenameExtension(filename);
		if (ext != null) {
			mediaTypes = fileExtensionToMediaTypes.get(ext.toLowerCase(Locale.ENGLISH));
		}
		return (mediaTypes != null ? mediaTypes : Collections.emptyList());
	}

}

相关信息

spring 源码目录

相关文章

spring CacheControl 源码

spring ContentDisposition 源码

spring DefaultHttpStatusCode 源码

spring HttpCookie 源码

spring HttpEntity 源码

spring HttpHeaders 源码

spring HttpInputMessage 源码

spring HttpLogging 源码

spring HttpMessage 源码

spring HttpMethod 源码