2019-04-30 自从用了Gitbook 简书用的都少了，来个水贴 MimeType OR MediaType

import static org.springframework.http.MediaType.APPLICATION_JSON_VALUE;

import static org.springframework.util.MimeTypeUtils.APPLICATION_JSON_VALUE;

/*
 * Copyright 2002-2018 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
 *
 *      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 org.springframework.http;

import java.io.Serializable;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.InvalidMimeTypeException;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;
import org.springframework.util.StringUtils;

/**
 * A subclass of {@link MimeType} that adds support for quality parameters
 * as defined in the HTTP specification.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @author Kazuki Shimizu
 * @since 3.0
 * @see <a href="http://tools.ietf.org/html/rfc7231#section-3.1.1.1">
 *     HTTP 1.1: Semantics and Content, section 3.1.1.1</a>
 */
public class MediaType extends MimeType implements Serializable {

    private static final long serialVersionUID = 2069937152339670231L;

    /**
     * Public constant media type that includes all media ranges (i.e. "&#42;/&#42;").
     */
    public static final MediaType ALL;

    /**
     * A String equivalent of {@link MediaType#ALL}.
     */
    public static final String ALL_VALUE = "*/*";

    /**
     *  Public constant media type for {@code application/atom+xml}.
     */
    public static final MediaType APPLICATION_ATOM_XML;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_ATOM_XML}.
     */
    public static final String APPLICATION_ATOM_XML_VALUE = "application/atom+xml";

    /**
     * Public constant media type for {@code application/x-www-form-urlencoded}.
     */
    public static final MediaType APPLICATION_FORM_URLENCODED;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_FORM_URLENCODED}.
     */
    public static final String APPLICATION_FORM_URLENCODED_VALUE = "application/x-www-form-urlencoded";

    /**
     * Public constant media type for {@code application/json}.
     * @see #APPLICATION_JSON_UTF8
     */
    public static final MediaType APPLICATION_JSON;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_JSON}.
     * @see #APPLICATION_JSON_UTF8_VALUE
     */
    public static final String APPLICATION_JSON_VALUE = "application/json";

    /**
     * Public constant media type for {@code application/json;charset=UTF-8}.
     *
     * <p>This {@link MediaType#APPLICATION_JSON} variant should be used to set JSON
     * content type because while
     * <a href="https://tools.ietf.org/html/rfc7159#section-11">RFC7159</a>
     * clearly states that "no charset parameter is defined for this registration", some
     * browsers require it for interpreting correctly UTF-8 special characters.
     */
    public static final MediaType APPLICATION_JSON_UTF8;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_JSON_UTF8}.
     *
     * <p>This {@link MediaType#APPLICATION_JSON_VALUE} variant should be used to set JSON
     * content type because while
     * <a href="https://tools.ietf.org/html/rfc7159#section-11">RFC7159</a>
     * clearly states that "no charset parameter is defined for this registration", some
     * browsers require it for interpreting correctly UTF-8 special characters.
     */
    public static final String APPLICATION_JSON_UTF8_VALUE = "application/json;charset=UTF-8";

    /**
     * Public constant media type for {@code application/octet-stream}.
     */
    public static final MediaType APPLICATION_OCTET_STREAM;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_OCTET_STREAM}.
     */
    public static final String APPLICATION_OCTET_STREAM_VALUE = "application/octet-stream";

    /**
     * Public constant media type for {@code application/pdf}.
     * @since 4.3
     */
    public static final MediaType APPLICATION_PDF;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_PDF}.
     * @since 4.3
     */
    public static final String APPLICATION_PDF_VALUE = "application/pdf";

    /**
     * Public constant media type for {@code application/problem+json}.
     * @since 5.0
     * @see <a href="https://tools.ietf.org/html/rfc7807#section-6.1">
     *     Problem Details for HTTP APIs, 6.1. application/problem+json</a>
     */
    public static final MediaType APPLICATION_PROBLEM_JSON;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_PROBLEM_JSON}.
     * @since 5.0
     */
    public static final String APPLICATION_PROBLEM_JSON_VALUE = "application/problem+json";

    /**
     * Public constant media type for {@code application/problem+json}.
     * @since 5.0
     * @see <a href="https://tools.ietf.org/html/rfc7807#section-6.1">
     *     Problem Details for HTTP APIs, 6.1. application/problem+json</a>
     */
    public static final MediaType APPLICATION_PROBLEM_JSON_UTF8;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_PROBLEM_JSON_UTF8}.
     * @since 5.0
     */
    public static final String APPLICATION_PROBLEM_JSON_UTF8_VALUE = "application/problem+json;charset=UTF-8";

    /**
     * Public constant media type for {@code application/problem+xml}.
     * @since 5.0
     * @see <a href="https://tools.ietf.org/html/rfc7807#section-6.2">
     *     Problem Details for HTTP APIs, 6.2. application/problem+xml</a>
     */
    public static final MediaType APPLICATION_PROBLEM_XML;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_PROBLEM_XML}.
     * @since 5.0
     */
    public static final String APPLICATION_PROBLEM_XML_VALUE = "application/problem+xml";

    /**
     * Public constant media type for {@code application/rss+xml}.
     * @since 4.3.6
     */
    public static final MediaType APPLICATION_RSS_XML;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_RSS_XML}.
     * @since 4.3.6
     */
    public static final String APPLICATION_RSS_XML_VALUE = "application/rss+xml";

    /**
     * Public constant media type for {@code application/stream+json}.
     * @since 5.0
     */
    public static final MediaType APPLICATION_STREAM_JSON;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_STREAM_JSON}.
     * @since 5.0
     */
    public static final String APPLICATION_STREAM_JSON_VALUE = "application/stream+json";

    /**
     * Public constant media type for {@code application/xhtml+xml}.
     */
    public static final MediaType APPLICATION_XHTML_XML;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_XHTML_XML}.
     */
    public static final String APPLICATION_XHTML_XML_VALUE = "application/xhtml+xml";

    /**
     * Public constant media type for {@code application/xml}.
     */
    public static final MediaType APPLICATION_XML;

    /**
     * A String equivalent of {@link MediaType#APPLICATION_XML}.
     */
    public static final String APPLICATION_XML_VALUE = "application/xml";

    /**
     * Public constant media type for {@code image/gif}.
     */
    public static final MediaType IMAGE_GIF;

    /**
     * A String equivalent of {@link MediaType#IMAGE_GIF}.
     */
    public static final String IMAGE_GIF_VALUE = "image/gif";

    /**
     * Public constant media type for {@code image/jpeg}.
     */
    public static final MediaType IMAGE_JPEG;

    /**
     * A String equivalent of {@link MediaType#IMAGE_JPEG}.
     */
    public static final String IMAGE_JPEG_VALUE = "image/jpeg";

    /**
     * Public constant media type for {@code image/png}.
     */
    public static final MediaType IMAGE_PNG;

    /**
     * A String equivalent of {@link MediaType#IMAGE_PNG}.
     */
    public static final String IMAGE_PNG_VALUE = "image/png";

    /**
     * Public constant media type for {@code multipart/form-data}.
     */
    public static final MediaType MULTIPART_FORM_DATA;

    /**
     * A String equivalent of {@link MediaType#MULTIPART_FORM_DATA}.
     */
    public static final String MULTIPART_FORM_DATA_VALUE = "multipart/form-data";

    /**
     * Public constant media type for {@code text/event-stream}.
     * @since 4.3.6
     * @see <a href="https://www.w3.org/TR/eventsource/">Server-Sent Events W3C recommendation</a>
     */
    public static final MediaType TEXT_EVENT_STREAM;

    /**
     * A String equivalent of {@link MediaType#TEXT_EVENT_STREAM}.
     * @since 4.3.6
     */
    public static final String TEXT_EVENT_STREAM_VALUE = "text/event-stream";

    /**
     * Public constant media type for {@code text/html}.
     */
    public static final MediaType TEXT_HTML;

    /**
     * A String equivalent of {@link MediaType#TEXT_HTML}.
     */
    public static final String TEXT_HTML_VALUE = "text/html";

    /**
     * Public constant media type for {@code text/markdown}.
     * @since 4.3
     */
    public static final MediaType TEXT_MARKDOWN;

    /**
     * A String equivalent of {@link MediaType#TEXT_MARKDOWN}.
     * @since 4.3
     */
    public static final String TEXT_MARKDOWN_VALUE = "text/markdown";

    /**
     * Public constant media type for {@code text/plain}.
     */
    public static final MediaType TEXT_PLAIN;

    /**
     * A String equivalent of {@link MediaType#TEXT_PLAIN}.
     */
    public static final String TEXT_PLAIN_VALUE = "text/plain";

    /**
     * Public constant media type for {@code text/xml}.
     */
    public static final MediaType TEXT_XML;

    /**
     * A String equivalent of {@link MediaType#TEXT_XML}.
     */
    public static final String TEXT_XML_VALUE = "text/xml";

    private static final String PARAM_QUALITY_FACTOR = "q";


    static {
        ALL = valueOf(ALL_VALUE);
        APPLICATION_ATOM_XML = valueOf(APPLICATION_ATOM_XML_VALUE);
        APPLICATION_FORM_URLENCODED = valueOf(APPLICATION_FORM_URLENCODED_VALUE);
        APPLICATION_JSON = valueOf(APPLICATION_JSON_VALUE);
        APPLICATION_JSON_UTF8 = valueOf(APPLICATION_JSON_UTF8_VALUE);
        APPLICATION_OCTET_STREAM = valueOf(APPLICATION_OCTET_STREAM_VALUE);
        APPLICATION_PDF = valueOf(APPLICATION_PDF_VALUE);
        APPLICATION_PROBLEM_JSON = valueOf(APPLICATION_PROBLEM_JSON_VALUE);
        APPLICATION_PROBLEM_JSON_UTF8 = valueOf(APPLICATION_PROBLEM_JSON_UTF8_VALUE);
        APPLICATION_PROBLEM_XML = valueOf(APPLICATION_PROBLEM_XML_VALUE);
        APPLICATION_RSS_XML = valueOf(APPLICATION_RSS_XML_VALUE);
        APPLICATION_STREAM_JSON = valueOf(APPLICATION_STREAM_JSON_VALUE);
        APPLICATION_XHTML_XML = valueOf(APPLICATION_XHTML_XML_VALUE);
        APPLICATION_XML = valueOf(APPLICATION_XML_VALUE);
        IMAGE_GIF = valueOf(IMAGE_GIF_VALUE);
        IMAGE_JPEG = valueOf(IMAGE_JPEG_VALUE);
        IMAGE_PNG = valueOf(IMAGE_PNG_VALUE);
        MULTIPART_FORM_DATA = valueOf(MULTIPART_FORM_DATA_VALUE);
        TEXT_EVENT_STREAM = valueOf(TEXT_EVENT_STREAM_VALUE);
        TEXT_HTML = valueOf(TEXT_HTML_VALUE);
        TEXT_MARKDOWN = valueOf(TEXT_MARKDOWN_VALUE);
        TEXT_PLAIN = valueOf(TEXT_PLAIN_VALUE);
        TEXT_XML = valueOf(TEXT_XML_VALUE);
    }


    /**
     * Create a new {@code MediaType} for the given primary type.
     * <p>The {@linkplain #getSubtype() subtype} is set to "&#42;", parameters empty.
     * @param type the primary type
     * @throws IllegalArgumentException if any of the parameters contain illegal characters
     */
    public MediaType(String type) {
        super(type);
    }

    /**
     * Create a new {@code MediaType} for the given primary type and subtype.
     * <p>The parameters are empty.
     * @param type the primary type
     * @param subtype the subtype
     * @throws IllegalArgumentException if any of the parameters contain illegal characters
     */
    public MediaType(String type, String subtype) {
        super(type, subtype, Collections.emptyMap());
    }

    /**
     * Create a new {@code MediaType} for the given type, subtype, and character set.
     * @param type the primary type
     * @param subtype the subtype
     * @param charset the character set
     * @throws IllegalArgumentException if any of the parameters contain illegal characters
     */
    public MediaType(String type, String subtype, Charset charset) {
        super(type, subtype, charset);
    }

    /**
     * Create a new {@code MediaType} for the given type, subtype, and quality value.
     * @param type the primary type
     * @param subtype the subtype
     * @param qualityValue the quality value
     * @throws IllegalArgumentException if any of the parameters contain illegal characters
     */
    public MediaType(String type, String subtype, double qualityValue) {
        this(type, subtype, Collections.singletonMap(PARAM_QUALITY_FACTOR, Double.toString(qualityValue)));
    }

    /**
     * Copy-constructor that copies the type, subtype and parameters of the given
     * {@code MediaType}, and allows to set the specified character set.
     * @param other the other media type
     * @param charset the character set
     * @throws IllegalArgumentException if any of the parameters contain illegal characters
     * @since 4.3
     */
    public MediaType(MediaType other, Charset charset) {
        super(other, charset);
    }

    /**
     * Copy-constructor that copies the type and subtype of the given {@code MediaType},
     * and allows for different parameter.
     * @param other the other media type
     * @param parameters the parameters, may be {@code null}
     * @throws IllegalArgumentException if any of the parameters contain illegal characters
     */
    public MediaType(MediaType other, @Nullable Map<String, String> parameters) {
        super(other.getType(), other.getSubtype(), parameters);
    }

    /**
     * Create a new {@code MediaType} for the given type, subtype, and parameters.
     * @param type the primary type
     * @param subtype the subtype
     * @param parameters the parameters, may be {@code null}
     * @throws IllegalArgumentException if any of the parameters contain illegal characters
     */
    public MediaType(String type, String subtype, @Nullable Map<String, String> parameters) {
        super(type, subtype, parameters);
    }


    @Override
    protected void checkParameters(String attribute, String value) {
        super.checkParameters(attribute, value);
        if (PARAM_QUALITY_FACTOR.equals(attribute)) {
            value = unquote(value);
            double d = Double.parseDouble(value);
            Assert.isTrue(d >= 0D && d <= 1D,
                    "Invalid quality value \"" + value + "\": should be between 0.0 and 1.0");
        }
    }

    /**
     * Return the quality factor, as indicated by a {@code q} parameter, if any.
     * Defaults to {@code 1.0}.
     * @return the quality factor as double value
     */
    public double getQualityValue() {
        String qualityFactor = getParameter(PARAM_QUALITY_FACTOR);
        return (qualityFactor != null ? Double.parseDouble(unquote(qualityFactor)) : 1D);
    }

    /**
     * Indicate whether this {@code MediaType} includes the given media type.
     * <p>For instance, {@code text/*} includes {@code text/plain} and {@code text/html},
     * and {@code application/*+xml} includes {@code application/soap+xml}, etc.
     * This method is <b>not</b> symmetric.
     * <p>Simply calls {@link #includes(MimeType)} but declared with a
     * {@code MediaType} parameter for binary backwards compatibility.
     * @param other the reference media type with which to compare
     * @return {@code true} if this media type includes the given media type;
     * {@code false} otherwise
     */
    public boolean includes(@Nullable MediaType other) {
        return super.includes(other);
    }

    /**
     * Indicate whether this {@code MediaType} is compatible with the given media type.
     * <p>For instance, {@code text/*} is compatible with {@code text/plain},
     * {@code text/html}, and vice versa. In effect, this method is similar to
     * {@link #includes}, except that it <b>is</b> symmetric.
     * <p>Simply calls {@link #isCompatibleWith(MimeType)} but declared with a
     * {@code MediaType} parameter for binary backwards compatibility.
     * @param other the reference media type with which to compare
     * @return {@code true} if this media type is compatible with the given media type;
     * {@code false} otherwise
     */
    public boolean isCompatibleWith(@Nullable MediaType other) {
        return super.isCompatibleWith(other);
    }

    /**
     * Return a replica of this instance with the quality value of the given {@code MediaType}.
     * @return the same instance if the given MediaType doesn't have a quality value,
     * or a new one otherwise
     */
    public MediaType copyQualityValue(MediaType mediaType) {
        if (!mediaType.getParameters().containsKey(PARAM_QUALITY_FACTOR)) {
            return this;
        }
        Map<String, String> params = new LinkedHashMap<>(getParameters());
        params.put(PARAM_QUALITY_FACTOR, mediaType.getParameters().get(PARAM_QUALITY_FACTOR));
        return new MediaType(this, params);
    }

    /**
     * Return a replica of this instance with its quality value removed.
     * @return the same instance if the media type doesn't contain a quality value,
     * or a new one otherwise
     */
    public MediaType removeQualityValue() {
        if (!getParameters().containsKey(PARAM_QUALITY_FACTOR)) {
            return this;
        }
        Map<String, String> params = new LinkedHashMap<>(getParameters());
        params.remove(PARAM_QUALITY_FACTOR);
        return new MediaType(this, params);
    }


    /**
     * Parse the given String value into a {@code MediaType} object,
     * with this method name following the 'valueOf' naming convention
     * (as supported by {@link org.springframework.core.convert.ConversionService}.
     * @param value the string to parse
     * @throws InvalidMediaTypeException if the media type value cannot be parsed
     * @see #parseMediaType(String)
     */
    public static MediaType valueOf(String value) {
        return parseMediaType(value);
    }

    /**
     * Parse the given String into a single {@code MediaType}.
     * @param mediaType the string to parse
     * @return the media type
     * @throws InvalidMediaTypeException if the media type value cannot be parsed
     */
    public static MediaType parseMediaType(String mediaType) {
        MimeType type;
        try {
            type = MimeTypeUtils.parseMimeType(mediaType);
        }
        catch (InvalidMimeTypeException ex) {
            throw new InvalidMediaTypeException(ex);
        }
        try {
            return new MediaType(type.getType(), type.getSubtype(), type.getParameters());
        }
        catch (IllegalArgumentException ex) {
            throw new InvalidMediaTypeException(mediaType, ex.getMessage());
        }
    }

    /**
     * Parse the comma-separated string into a list of {@code MediaType} objects.
     * <p>This method can be used to parse an Accept or Content-Type header.
     * @param mediaTypes the string to parse
     * @return the list of media types
     * @throws InvalidMediaTypeException if the media type value cannot be parsed
     */
    public static List<MediaType> parseMediaTypes(@Nullable String mediaTypes) {
        if (!StringUtils.hasLength(mediaTypes)) {
            return Collections.emptyList();
        }
        return MimeTypeUtils.tokenize(mediaTypes).stream()
                .map(MediaType::parseMediaType).collect(Collectors.toList());
    }

    /**
     * Parse the given list of (potentially) comma-separated strings into a
     * list of {@code MediaType} objects.
     * <p>This method can be used to parse an Accept or Content-Type header.
     * @param mediaTypes the string to parse
     * @return the list of media types
     * @throws InvalidMediaTypeException if the media type value cannot be parsed
     * @since 4.3.2
     */
    public static List<MediaType> parseMediaTypes(@Nullable List<String> mediaTypes) {
        if (CollectionUtils.isEmpty(mediaTypes)) {
            return Collections.emptyList();
        }
        else if (mediaTypes.size() == 1) {
            return parseMediaTypes(mediaTypes.get(0));
        }
        else {
            List<MediaType> result = new ArrayList<>(8);
            for (String mediaType : mediaTypes) {
                result.addAll(parseMediaTypes(mediaType));
            }
            return result;
        }
    }

    /**
     * Re-create the given mime types as media types.
     * @since 5.0
     */
    public static List<MediaType> asMediaTypes(List<MimeType> mimeTypes) {
        return mimeTypes.stream().map(MediaType::asMediaType).collect(Collectors.toList());
    }

    /**
     * Re-create the given mime type as a media type.
     * @since 5.0
     */
    public static MediaType asMediaType(MimeType mimeType) {
        if (mimeType instanceof MediaType) {
            return (MediaType) mimeType;
        }
        return new MediaType(mimeType.getType(), mimeType.getSubtype(), mimeType.getParameters());
    }

    /**
     * Return a string representation of the given list of {@code MediaType} objects.
     * <p>This method can be used to for an {@code Accept} or {@code Content-Type} header.
     * @param mediaTypes the media types to create a string representation for
     * @return the string representation
     */
    public static String toString(Collection<MediaType> mediaTypes) {
        return MimeTypeUtils.toString(mediaTypes);
    }

    /**
     * Sorts the given list of {@code MediaType} objects by specificity.
     * <p>Given two media types:
     * <ol>
     * <li>if either media type has a {@linkplain #isWildcardType() wildcard type}, then the media type without the
     * wildcard is ordered before the other.</li>
     * <li>if the two media types have different {@linkplain #getType() types}, then they are considered equal and
     * remain their current order.</li>
     * <li>if either media type has a {@linkplain #isWildcardSubtype() wildcard subtype}, then the media type without
     * the wildcard is sorted before the other.</li>
     * <li>if the two media types have different {@linkplain #getSubtype() subtypes}, then they are considered equal
     * and remain their current order.</li>
     * <li>if the two media types have different {@linkplain #getQualityValue() quality value}, then the media type
     * with the highest quality value is ordered before the other.</li>
     * <li>if the two media types have a different amount of {@linkplain #getParameter(String) parameters}, then the
     * media type with the most parameters is ordered before the other.</li>
     * </ol>
     * <p>For example:
     * <blockquote>audio/basic &lt; audio/* &lt; *&#047;*</blockquote>
     * <blockquote>audio/* &lt; audio/*;q=0.7; audio/*;q=0.3</blockquote>
     * <blockquote>audio/basic;level=1 &lt; audio/basic</blockquote>
     * <blockquote>audio/basic == text/html</blockquote>
     * <blockquote>audio/basic == audio/wave</blockquote>
     * @param mediaTypes the list of media types to be sorted
     * @see <a href="http://tools.ietf.org/html/rfc7231#section-5.3.2">HTTP 1.1: Semantics
     * and Content, section 5.3.2</a>
     */
    public static void sortBySpecificity(List<MediaType> mediaTypes) {
        Assert.notNull(mediaTypes, "'mediaTypes' must not be null");
        if (mediaTypes.size() > 1) {
            mediaTypes.sort(SPECIFICITY_COMPARATOR);
        }
    }

    /**
     * Sorts the given list of {@code MediaType} objects by quality value.
     * <p>Given two media types:
     * <ol>
     * <li>if the two media types have different {@linkplain #getQualityValue() quality value}, then the media type
     * with the highest quality value is ordered before the other.</li>
     * <li>if either media type has a {@linkplain #isWildcardType() wildcard type}, then the media type without the
     * wildcard is ordered before the other.</li>
     * <li>if the two media types have different {@linkplain #getType() types}, then they are considered equal and
     * remain their current order.</li>
     * <li>if either media type has a {@linkplain #isWildcardSubtype() wildcard subtype}, then the media type without
     * the wildcard is sorted before the other.</li>
     * <li>if the two media types have different {@linkplain #getSubtype() subtypes}, then they are considered equal
     * and remain their current order.</li>
     * <li>if the two media types have a different amount of {@linkplain #getParameter(String) parameters}, then the
     * media type with the most parameters is ordered before the other.</li>
     * </ol>
     * @param mediaTypes the list of media types to be sorted
     * @see #getQualityValue()
     */
    public static void sortByQualityValue(List<MediaType> mediaTypes) {
        Assert.notNull(mediaTypes, "'mediaTypes' must not be null");
        if (mediaTypes.size() > 1) {
            mediaTypes.sort(QUALITY_VALUE_COMPARATOR);
        }
    }

    /**
     * Sorts the given list of {@code MediaType} objects by specificity as the
     * primary criteria and quality value the secondary.
     * @see MediaType#sortBySpecificity(List)
     * @see MediaType#sortByQualityValue(List)
     */
    public static void sortBySpecificityAndQuality(List<MediaType> mediaTypes) {
        Assert.notNull(mediaTypes, "'mediaTypes' must not be null");
        if (mediaTypes.size() > 1) {
            mediaTypes.sort(MediaType.SPECIFICITY_COMPARATOR.thenComparing(MediaType.QUALITY_VALUE_COMPARATOR));
        }
    }


    /**
     * Comparator used by {@link #sortByQualityValue(List)}.
     */
    public static final Comparator<MediaType> QUALITY_VALUE_COMPARATOR = (mediaType1, mediaType2) -> {
        double quality1 = mediaType1.getQualityValue();
        double quality2 = mediaType2.getQualityValue();
        int qualityComparison = Double.compare(quality2, quality1);
        if (qualityComparison != 0) {
            return qualityComparison;  // audio/*;q=0.7 < audio/*;q=0.3
        }
        else if (mediaType1.isWildcardType() && !mediaType2.isWildcardType()) {  // */* < audio/*
            return 1;
        }
        else if (mediaType2.isWildcardType() && !mediaType1.isWildcardType()) {  // audio/* > */*
            return -1;
        }
        else if (!mediaType1.getType().equals(mediaType2.getType())) {  // audio/basic == text/html
            return 0;
        }
        else {  // mediaType1.getType().equals(mediaType2.getType())
            if (mediaType1.isWildcardSubtype() && !mediaType2.isWildcardSubtype()) {  // audio/* < audio/basic
                return 1;
            }
            else if (mediaType2.isWildcardSubtype() && !mediaType1.isWildcardSubtype()) {  // audio/basic > audio/*
                return -1;
            }
            else if (!mediaType1.getSubtype().equals(mediaType2.getSubtype())) {  // audio/basic == audio/wave
                return 0;
            }
            else {
                int paramsSize1 = mediaType1.getParameters().size();
                int paramsSize2 = mediaType2.getParameters().size();
                return Integer.compare(paramsSize2, paramsSize1);  // audio/basic;level=1 < audio/basic
            }
        }
    };


    /**
     * Comparator used by {@link #sortBySpecificity(List)}.
     */
    public static final Comparator<MediaType> SPECIFICITY_COMPARATOR = new SpecificityComparator<MediaType>() {

        @Override
        protected int compareParameters(MediaType mediaType1, MediaType mediaType2) {
            double quality1 = mediaType1.getQualityValue();
            double quality2 = mediaType2.getQualityValue();
            int qualityComparison = Double.compare(quality2, quality1);
            if (qualityComparison != 0) {
                return qualityComparison;  // audio/*;q=0.7 < audio/*;q=0.3
            }
            return super.compareParameters(mediaType1, mediaType2);
        }
    };

}

/*
 * Copyright 2002-2019 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
 *
 *      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 org.springframework.util;

import java.nio.charset.StandardCharsets;
import java.nio.charset.UnsupportedCharsetException;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.stream.Collectors;

import org.springframework.lang.Nullable;

/**
 * Miscellaneous {@link MimeType} utility methods.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Dimitrios Liapis
 * @since 4.0
 */
public abstract class MimeTypeUtils {

    private static final byte[] BOUNDARY_CHARS =
            new byte[] {'-', '_', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
                    'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A',
                    'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U',
                    'V', 'W', 'X', 'Y', 'Z'};

    /**
     * Comparator used by {@link #sortBySpecificity(List)}.
     */
    public static final Comparator<MimeType> SPECIFICITY_COMPARATOR = new MimeType.SpecificityComparator<>();

    /**
     * Public constant mime type that includes all media ranges (i.e. "&#42;/&#42;").
     */
    public static final MimeType ALL;

    /**
     * A String equivalent of {@link MimeTypeUtils#ALL}.
     */
    public static final String ALL_VALUE = "*/*";

    /**
     * Public constant mime type for {@code application/json}.
     * */
    public static final MimeType APPLICATION_JSON;

    /**
     * A String equivalent of {@link MimeTypeUtils#APPLICATION_JSON}.
     */
    public static final String APPLICATION_JSON_VALUE = "application/json";

    /**
     * Public constant mime type for {@code application/octet-stream}.
     *  */
    public static final MimeType APPLICATION_OCTET_STREAM;

    /**
     * A String equivalent of {@link MimeTypeUtils#APPLICATION_OCTET_STREAM}.
     */
    public static final String APPLICATION_OCTET_STREAM_VALUE = "application/octet-stream";

    /**
     * Public constant mime type for {@code application/xml}.
     */
    public static final MimeType APPLICATION_XML;

    /**
     * A String equivalent of {@link MimeTypeUtils#APPLICATION_XML}.
     */
    public static final String APPLICATION_XML_VALUE = "application/xml";

    /**
     * Public constant mime type for {@code image/gif}.
     */
    public static final MimeType IMAGE_GIF;

    /**
     * A String equivalent of {@link MimeTypeUtils#IMAGE_GIF}.
     */
    public static final String IMAGE_GIF_VALUE = "image/gif";

    /**
     * Public constant mime type for {@code image/jpeg}.
     */
    public static final MimeType IMAGE_JPEG;

    /**
     * A String equivalent of {@link MimeTypeUtils#IMAGE_JPEG}.
     */
    public static final String IMAGE_JPEG_VALUE = "image/jpeg";

    /**
     * Public constant mime type for {@code image/png}.
     */
    public static final MimeType IMAGE_PNG;

    /**
     * A String equivalent of {@link MimeTypeUtils#IMAGE_PNG}.
     */
    public static final String IMAGE_PNG_VALUE = "image/png";

    /**
     * Public constant mime type for {@code text/html}.
     *  */
    public static final MimeType TEXT_HTML;

    /**
     * A String equivalent of {@link MimeTypeUtils#TEXT_HTML}.
     */
    public static final String TEXT_HTML_VALUE = "text/html";

    /**
     * Public constant mime type for {@code text/plain}.
     *  */
    public static final MimeType TEXT_PLAIN;

    /**
     * A String equivalent of {@link MimeTypeUtils#TEXT_PLAIN}.
     */
    public static final String TEXT_PLAIN_VALUE = "text/plain";

    /**
     * Public constant mime type for {@code text/xml}.
     *  */
    public static final MimeType TEXT_XML;

    /**
     * A String equivalent of {@link MimeTypeUtils#TEXT_XML}.
     */
    public static final String TEXT_XML_VALUE = "text/xml";


    @Nullable
    private static volatile Random random;

    static {
        ALL = MimeType.valueOf(ALL_VALUE);
        APPLICATION_JSON = MimeType.valueOf(APPLICATION_JSON_VALUE);
        APPLICATION_OCTET_STREAM = MimeType.valueOf(APPLICATION_OCTET_STREAM_VALUE);
        APPLICATION_XML = MimeType.valueOf(APPLICATION_XML_VALUE);
        IMAGE_GIF = MimeType.valueOf(IMAGE_GIF_VALUE);
        IMAGE_JPEG = MimeType.valueOf(IMAGE_JPEG_VALUE);
        IMAGE_PNG = MimeType.valueOf(IMAGE_PNG_VALUE);
        TEXT_HTML = MimeType.valueOf(TEXT_HTML_VALUE);
        TEXT_PLAIN = MimeType.valueOf(TEXT_PLAIN_VALUE);
        TEXT_XML = MimeType.valueOf(TEXT_XML_VALUE);
    }


    /**
     * Parse the given String into a single {@code MimeType}.
     * @param mimeType the string to parse
     * @return the mime type
     * @throws InvalidMimeTypeException if the string cannot be parsed
     */
    public static MimeType parseMimeType(String mimeType) {
        if (!StringUtils.hasLength(mimeType)) {
            throw new InvalidMimeTypeException(mimeType, "'mimeType' must not be empty");
        }

        int index = mimeType.indexOf(';');
        String fullType = (index >= 0 ? mimeType.substring(0, index) : mimeType).trim();
        if (fullType.isEmpty()) {
            throw new InvalidMimeTypeException(mimeType, "'mimeType' must not be empty");
        }

        // java.net.HttpURLConnection returns a *; q=.2 Accept header
        if (MimeType.WILDCARD_TYPE.equals(fullType)) {
            fullType = "*/*";
        }
        int subIndex = fullType.indexOf('/');
        if (subIndex == -1) {
            throw new InvalidMimeTypeException(mimeType, "does not contain '/'");
        }
        if (subIndex == fullType.length() - 1) {
            throw new InvalidMimeTypeException(mimeType, "does not contain subtype after '/'");
        }
        String type = fullType.substring(0, subIndex);
        String subtype = fullType.substring(subIndex + 1, fullType.length());
        if (MimeType.WILDCARD_TYPE.equals(type) && !MimeType.WILDCARD_TYPE.equals(subtype)) {
            throw new InvalidMimeTypeException(mimeType, "wildcard type is legal only in '*/*' (all mime types)");
        }

        Map<String, String> parameters = null;
        do {
            int nextIndex = index + 1;
            boolean quoted = false;
            while (nextIndex < mimeType.length()) {
                char ch = mimeType.charAt(nextIndex);
                if (ch == ';') {
                    if (!quoted) {
                        break;
                    }
                }
                else if (ch == '"') {
                    quoted = !quoted;
                }
                nextIndex++;
            }
            String parameter = mimeType.substring(index + 1, nextIndex).trim();
            if (parameter.length() > 0) {
                if (parameters == null) {
                    parameters = new LinkedHashMap<>(4);
                }
                int eqIndex = parameter.indexOf('=');
                if (eqIndex >= 0) {
                    String attribute = parameter.substring(0, eqIndex).trim();
                    String value = parameter.substring(eqIndex + 1, parameter.length()).trim();
                    parameters.put(attribute, value);
                }
            }
            index = nextIndex;
        }
        while (index < mimeType.length());

        try {
            return new MimeType(type, subtype, parameters);
        }
        catch (UnsupportedCharsetException ex) {
            throw new InvalidMimeTypeException(mimeType, "unsupported charset '" + ex.getCharsetName() + "'");
        }
        catch (IllegalArgumentException ex) {
            throw new InvalidMimeTypeException(mimeType, ex.getMessage());
        }
    }

    /**
     * Parse the comma-separated string into a list of {@code MimeType} objects.
     * @param mimeTypes the string to parse
     * @return the list of mime types
     * @throws InvalidMimeTypeException if the string cannot be parsed
     */
    public static List<MimeType> parseMimeTypes(String mimeTypes) {
        if (!StringUtils.hasLength(mimeTypes)) {
            return Collections.emptyList();
        }
        return tokenize(mimeTypes).stream()
                .map(MimeTypeUtils::parseMimeType).collect(Collectors.toList());
    }


    /**
     * Tokenize the given comma-separated string of {@code MimeType} objects
     * into a {@code List<String>}. Unlike simple tokenization by ",", this
     * method takes into account quoted parameters.
     * @param mimeTypes the string to tokenize
     * @return the list of tokens
     * @since 5.1.3
     */
    public static List<String> tokenize(String mimeTypes) {
        if (!StringUtils.hasLength(mimeTypes)) {
            return Collections.emptyList();
        }
        List<String> tokens = new ArrayList<>();
        boolean inQuotes = false;
        int startIndex = 0;
        int i = 0;
        while (i < mimeTypes.length()) {
            switch (mimeTypes.charAt(i)) {
                case '"':
                    inQuotes = !inQuotes;
                    break;
                case ',':
                    if (!inQuotes) {
                        tokens.add(mimeTypes.substring(startIndex, i));
                        startIndex = i + 1;
                    }
                    break;
                case '\\':
                    i++;
                    break;
            }
            i++;
        }
        tokens.add(mimeTypes.substring(startIndex));
        return tokens;
    }

    /**
     * Return a string representation of the given list of {@code MimeType} objects.
     * @param mimeTypes the string to parse
     * @return the list of mime types
     * @throws IllegalArgumentException if the String cannot be parsed
     */
    public static String toString(Collection<? extends MimeType> mimeTypes) {
        StringBuilder builder = new StringBuilder();
        for (Iterator<? extends MimeType> iterator = mimeTypes.iterator(); iterator.hasNext();) {
            MimeType mimeType = iterator.next();
            mimeType.appendTo(builder);
            if (iterator.hasNext()) {
                builder.append(", ");
            }
        }
        return builder.toString();
    }

    /**
     * Sorts the given list of {@code MimeType} objects by specificity.
     * <p>Given two mime types:
     * <ol>
     * <li>if either mime type has a {@linkplain MimeType#isWildcardType() wildcard type},
     * then the mime type without the wildcard is ordered before the other.</li>
     * <li>if the two mime types have different {@linkplain MimeType#getType() types},
     * then they are considered equal and remain their current order.</li>
     * <li>if either mime type has a {@linkplain MimeType#isWildcardSubtype() wildcard subtype}
     * , then the mime type without the wildcard is sorted before the other.</li>
     * <li>if the two mime types have different {@linkplain MimeType#getSubtype() subtypes},
     * then they are considered equal and remain their current order.</li>
     * <li>if the two mime types have a different amount of
     * {@linkplain MimeType#getParameter(String) parameters}, then the mime type with the most
     * parameters is ordered before the other.</li>
     * </ol>
     * <p>For example: <blockquote>audio/basic &lt; audio/* &lt; *&#047;*</blockquote>
     * <blockquote>audio/basic;level=1 &lt; audio/basic</blockquote>
     * <blockquote>audio/basic == text/html</blockquote> <blockquote>audio/basic ==
     * audio/wave</blockquote>
     * @param mimeTypes the list of mime types to be sorted
     * @see <a href="http://tools.ietf.org/html/rfc7231#section-5.3.2">HTTP 1.1: Semantics
     * and Content, section 5.3.2</a>
     */
    public static void sortBySpecificity(List<MimeType> mimeTypes) {
        Assert.notNull(mimeTypes, "'mimeTypes' must not be null");
        if (mimeTypes.size() > 1) {
            mimeTypes.sort(SPECIFICITY_COMPARATOR);
        }
    }


    /**
     * Lazily initialize the {@link SecureRandom} for {@link #generateMultipartBoundary()}.
     */
    private static Random initRandom() {
        Random randomToUse = random;
        if (randomToUse == null) {
            synchronized (MimeTypeUtils.class) {
                randomToUse = random;
                if (randomToUse == null) {
                    randomToUse = new SecureRandom();
                    random = randomToUse;
                }
            }
        }
        return randomToUse;
    }

    /**
     * Generate a random MIME boundary as bytes, often used in multipart mime types.
     */
    public static byte[] generateMultipartBoundary() {
        Random randomToUse = initRandom();
        byte[] boundary = new byte[randomToUse.nextInt(11) + 30];
        for (int i = 0; i < boundary.length; i++) {
            boundary[i] = BOUNDARY_CHARS[randomToUse.nextInt(BOUNDARY_CHARS.length)];
        }
        return boundary;
    }

    /**
     * Generate a random MIME boundary as String, often used in multipart mime types.
     */
    public static String generateMultipartBoundaryString() {
        return new String(generateMultipartBoundary(), StandardCharsets.US_ASCII);
    }

}