https://github.com/spring-projects/spring-framework: Spring Web (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2020 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.Serializable;
import java.net.InetSocketAddress;
import java.net.URI;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.StandardCharsets;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.time.Duration;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.util.ArrayList;
import java.util.Base64;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.StringJoiner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.LinkedCaseInsensitiveMap;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;


A data structure representing HTTP request or response headers, mapping String header names
to a list of String values, also offering accessors for common application-level data types.

In addition to the regular methods defined by Map, this class offers many common convenience methods, for example: 


Note that HttpHeaders generally treats header names in a case-insensitive manner. 
Author:Arjen Poutsma, Sebastien Deleuze, Brian Clozel, Juergen Hoeller, Josh Long, Sam Brannen
Since:3.0
/**
 * A data structure representing HTTP request or response headers, mapping String header names
 * to a list of String values, also offering accessors for common application-level data types.
 *
 * <p>In addition to the regular methods defined by {@link Map}, this class offers many common
 * convenience methods, for example:
 * <ul>
 * <li>{@link #getFirst(String)} returns the first value associated with a given header name</li>
 * <li>{@link #add(String, String)} adds a header value to the list of values for a header name</li>
 * <li>{@link #set(String, String)} sets the header value to a single string value</li>
 * </ul>
 *
 * <p>Note that {@code HttpHeaders} generally treats header names in a case-insensitive manner.
 *
 * @author Arjen Poutsma
 * @author Sebastien Deleuze
 * @author Brian Clozel
 * @author Juergen Hoeller
 * @author Josh Long
 * @author Sam Brannen
 * @since 3.0
 */
public class HttpHeaders implements MultiValueMap<String, String>, Serializable {

	private static final long serialVersionUID = -8578554704772377436L;


	
The HTTP Accept header field name. 
See Also:
/**
	 * The HTTP {@code Accept} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.3.2">Section 5.3.2 of RFC 7231</a>
	 */
	public static final String ACCEPT = "Accept";
	
The HTTP Accept-Charset header field name. 
See Also:
/**
	 * The HTTP {@code Accept-Charset} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.3.3">Section 5.3.3 of RFC 7231</a>
	 */
	public static final String ACCEPT_CHARSET = "Accept-Charset";
	
The HTTP Accept-Encoding header field name. 
See Also:
/**
	 * The HTTP {@code Accept-Encoding} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.3.4">Section 5.3.4 of RFC 7231</a>
	 */
	public static final String ACCEPT_ENCODING = "Accept-Encoding";
	
The HTTP Accept-Language header field name. 
See Also:
/**
	 * The HTTP {@code Accept-Language} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.3.5">Section 5.3.5 of RFC 7231</a>
	 */
	public static final String ACCEPT_LANGUAGE = "Accept-Language";
	
The HTTP Accept-Ranges header field name. 
See Also:
/**
	 * The HTTP {@code Accept-Ranges} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7233#section-2.3">Section 5.3.5 of RFC 7233</a>
	 */
	public static final String ACCEPT_RANGES = "Accept-Ranges";
	
The CORS Access-Control-Allow-Credentials response header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Allow-Credentials} response header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_ALLOW_CREDENTIALS = "Access-Control-Allow-Credentials";
	
The CORS Access-Control-Allow-Headers response header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Allow-Headers} response header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_ALLOW_HEADERS = "Access-Control-Allow-Headers";
	
The CORS Access-Control-Allow-Methods response header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Allow-Methods} response header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_ALLOW_METHODS = "Access-Control-Allow-Methods";
	
The CORS Access-Control-Allow-Origin response header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Allow-Origin} response header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_ALLOW_ORIGIN = "Access-Control-Allow-Origin";
	
The CORS Access-Control-Expose-Headers response header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Expose-Headers} response header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_EXPOSE_HEADERS = "Access-Control-Expose-Headers";
	
The CORS Access-Control-Max-Age response header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Max-Age} response header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_MAX_AGE = "Access-Control-Max-Age";
	
The CORS Access-Control-Request-Headers request header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Request-Headers} request header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_REQUEST_HEADERS = "Access-Control-Request-Headers";
	
The CORS Access-Control-Request-Method request header field name. 
See Also:
/**
	 * The CORS {@code Access-Control-Request-Method} request header field name.
	 * @see <a href="https://www.w3.org/TR/cors/">CORS W3C recommendation</a>
	 */
	public static final String ACCESS_CONTROL_REQUEST_METHOD = "Access-Control-Request-Method";
	
The HTTP Age header field name. 
See Also:
/**
	 * The HTTP {@code Age} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7234#section-5.1">Section 5.1 of RFC 7234</a>
	 */
	public static final String AGE = "Age";
	
The HTTP Allow header field name. 
See Also:
/**
	 * The HTTP {@code Allow} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.4.1">Section 7.4.1 of RFC 7231</a>
	 */
	public static final String ALLOW = "Allow";
	
The HTTP Authorization header field name. 
See Also:
/**
	 * The HTTP {@code Authorization} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7235#section-4.2">Section 4.2 of RFC 7235</a>
	 */
	public static final String AUTHORIZATION = "Authorization";
	
The HTTP Cache-Control header field name. 
See Also:
/**
	 * The HTTP {@code Cache-Control} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7234#section-5.2">Section 5.2 of RFC 7234</a>
	 */
	public static final String CACHE_CONTROL = "Cache-Control";
	
The HTTP Connection header field name. 
See Also:
/**
	 * The HTTP {@code Connection} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-6.1">Section 6.1 of RFC 7230</a>
	 */
	public static final String CONNECTION = "Connection";
	
The HTTP Content-Encoding header field name. 
See Also:
/**
	 * The HTTP {@code Content-Encoding} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-3.1.2.2">Section 3.1.2.2 of RFC 7231</a>
	 */
	public static final String CONTENT_ENCODING = "Content-Encoding";
	
The HTTP Content-Disposition header field name. 
See Also:
/**
	 * The HTTP {@code Content-Disposition} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc6266">RFC 6266</a>
	 */
	public static final String CONTENT_DISPOSITION = "Content-Disposition";
	
The HTTP Content-Language header field name. 
See Also:
/**
	 * The HTTP {@code Content-Language} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-3.1.3.2">Section 3.1.3.2 of RFC 7231</a>
	 */
	public static final String CONTENT_LANGUAGE = "Content-Language";
	
The HTTP Content-Length header field name. 
See Also:
/**
	 * The HTTP {@code Content-Length} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-3.3.2">Section 3.3.2 of RFC 7230</a>
	 */
	public static final String CONTENT_LENGTH = "Content-Length";
	
The HTTP Content-Location header field name. 
See Also:
/**
	 * The HTTP {@code Content-Location} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-3.1.4.2">Section 3.1.4.2 of RFC 7231</a>
	 */
	public static final String CONTENT_LOCATION = "Content-Location";
	
The HTTP Content-Range header field name. 
See Also:
/**
	 * The HTTP {@code Content-Range} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7233#section-4.2">Section 4.2 of RFC 7233</a>
	 */
	public static final String CONTENT_RANGE = "Content-Range";
	
The HTTP Content-Type header field name. 
See Also:
/**
	 * The HTTP {@code Content-Type} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-3.1.1.5">Section 3.1.1.5 of RFC 7231</a>
	 */
	public static final String CONTENT_TYPE = "Content-Type";
	
The HTTP Cookie header field name. 
See Also:
/**
	 * The HTTP {@code Cookie} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc2109#section-4.3.4">Section 4.3.4 of RFC 2109</a>
	 */
	public static final String COOKIE = "Cookie";
	
The HTTP Date header field name. 
See Also:
/**
	 * The HTTP {@code Date} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.1.2">Section 7.1.1.2 of RFC 7231</a>
	 */
	public static final String DATE = "Date";
	
The HTTP ETag header field name. 
See Also:
/**
	 * The HTTP {@code ETag} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-2.3">Section 2.3 of RFC 7232</a>
	 */
	public static final String ETAG = "ETag";
	
The HTTP Expect header field name. 
See Also:
/**
	 * The HTTP {@code Expect} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.1.1">Section 5.1.1 of RFC 7231</a>
	 */
	public static final String EXPECT = "Expect";
	
The HTTP Expires header field name. 
See Also:
/**
	 * The HTTP {@code Expires} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7234#section-5.3">Section 5.3 of RFC 7234</a>
	 */
	public static final String EXPIRES = "Expires";
	
The HTTP From header field name. 
See Also:
/**
	 * The HTTP {@code From} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.5.1">Section 5.5.1 of RFC 7231</a>
	 */
	public static final String FROM = "From";
	
The HTTP Host header field name. 
See Also:
/**
	 * The HTTP {@code Host} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-5.4">Section 5.4 of RFC 7230</a>
	 */
	public static final String HOST = "Host";
	
The HTTP If-Match header field name. 
See Also:
/**
	 * The HTTP {@code If-Match} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-3.1">Section 3.1 of RFC 7232</a>
	 */
	public static final String IF_MATCH = "If-Match";
	
The HTTP If-Modified-Since header field name. 
See Also:
/**
	 * The HTTP {@code If-Modified-Since} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-3.3">Section 3.3 of RFC 7232</a>
	 */
	public static final String IF_MODIFIED_SINCE = "If-Modified-Since";
	
The HTTP If-None-Match header field name. 
See Also:
/**
	 * The HTTP {@code If-None-Match} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-3.2">Section 3.2 of RFC 7232</a>
	 */
	public static final String IF_NONE_MATCH = "If-None-Match";
	
The HTTP If-Range header field name. 
See Also:
/**
	 * The HTTP {@code If-Range} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7233#section-3.2">Section 3.2 of RFC 7233</a>
	 */
	public static final String IF_RANGE = "If-Range";
	
The HTTP If-Unmodified-Since header field name. 
See Also:
/**
	 * The HTTP {@code If-Unmodified-Since} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-3.4">Section 3.4 of RFC 7232</a>
	 */
	public static final String IF_UNMODIFIED_SINCE = "If-Unmodified-Since";
	
The HTTP Last-Modified header field name. 
See Also:
/**
	 * The HTTP {@code Last-Modified} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-2.2">Section 2.2 of RFC 7232</a>
	 */
	public static final String LAST_MODIFIED = "Last-Modified";
	
The HTTP Link header field name. 
See Also:
/**
	 * The HTTP {@code Link} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc5988">RFC 5988</a>
	 */
	public static final String LINK = "Link";
	
The HTTP Location header field name. 
See Also:
/**
	 * The HTTP {@code Location} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.2">Section 7.1.2 of RFC 7231</a>
	 */
	public static final String LOCATION = "Location";
	
The HTTP Max-Forwards header field name. 
See Also:
/**
	 * The HTTP {@code Max-Forwards} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.1.2">Section 5.1.2 of RFC 7231</a>
	 */
	public static final String MAX_FORWARDS = "Max-Forwards";
	
The HTTP Origin header field name. 
See Also:
/**
	 * The HTTP {@code Origin} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc6454">RFC 6454</a>
	 */
	public static final String ORIGIN = "Origin";
	
The HTTP Pragma header field name. 
See Also:
/**
	 * The HTTP {@code Pragma} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7234#section-5.4">Section 5.4 of RFC 7234</a>
	 */
	public static final String PRAGMA = "Pragma";
	
The HTTP Proxy-Authenticate header field name. 
See Also:
/**
	 * The HTTP {@code Proxy-Authenticate} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7235#section-4.3">Section 4.3 of RFC 7235</a>
	 */
	public static final String PROXY_AUTHENTICATE = "Proxy-Authenticate";
	
The HTTP Proxy-Authorization header field name. 
See Also:
/**
	 * The HTTP {@code Proxy-Authorization} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7235#section-4.4">Section 4.4 of RFC 7235</a>
	 */
	public static final String PROXY_AUTHORIZATION = "Proxy-Authorization";
	
The HTTP Range header field name. 
See Also:
/**
	 * The HTTP {@code Range} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7233#section-3.1">Section 3.1 of RFC 7233</a>
	 */
	public static final String RANGE = "Range";
	
The HTTP Referer header field name. 
See Also:
/**
	 * The HTTP {@code Referer} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.5.2">Section 5.5.2 of RFC 7231</a>
	 */
	public static final String REFERER = "Referer";
	
The HTTP Retry-After header field name. 
See Also:
/**
	 * The HTTP {@code Retry-After} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.3">Section 7.1.3 of RFC 7231</a>
	 */
	public static final String RETRY_AFTER = "Retry-After";
	
The HTTP Server header field name. 
See Also:
/**
	 * The HTTP {@code Server} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.4.2">Section 7.4.2 of RFC 7231</a>
	 */
	public static final String SERVER = "Server";
	
The HTTP Set-Cookie header field name. 
See Also:
/**
	 * The HTTP {@code Set-Cookie} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc2109#section-4.2.2">Section 4.2.2 of RFC 2109</a>
	 */
	public static final String SET_COOKIE = "Set-Cookie";
	
The HTTP Set-Cookie2 header field name. 
See Also:
/**
	 * The HTTP {@code Set-Cookie2} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc2965">RFC 2965</a>
	 */
	public static final String SET_COOKIE2 = "Set-Cookie2";
	
The HTTP TE header field name. 
See Also:
/**
	 * The HTTP {@code TE} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-4.3">Section 4.3 of RFC 7230</a>
	 */
	public static final String TE = "TE";
	
The HTTP Trailer header field name. 
See Also:
/**
	 * The HTTP {@code Trailer} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-4.4">Section 4.4 of RFC 7230</a>
	 */
	public static final String TRAILER = "Trailer";
	
The HTTP Transfer-Encoding header field name. 
See Also:
/**
	 * The HTTP {@code Transfer-Encoding} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-3.3.1">Section 3.3.1 of RFC 7230</a>
	 */
	public static final String TRANSFER_ENCODING = "Transfer-Encoding";
	
The HTTP Upgrade header field name. 
See Also:
/**
	 * The HTTP {@code Upgrade} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-6.7">Section 6.7 of RFC 7230</a>
	 */
	public static final String UPGRADE = "Upgrade";
	
The HTTP User-Agent header field name. 
See Also:
/**
	 * The HTTP {@code User-Agent} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-5.5.3">Section 5.5.3 of RFC 7231</a>
	 */
	public static final String USER_AGENT = "User-Agent";
	
The HTTP Vary header field name. 
See Also:
/**
	 * The HTTP {@code Vary} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.4">Section 7.1.4 of RFC 7231</a>
	 */
	public static final String VARY = "Vary";
	
The HTTP Via header field name. 
See Also:
/**
	 * The HTTP {@code Via} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7230#section-5.7.1">Section 5.7.1 of RFC 7230</a>
	 */
	public static final String VIA = "Via";
	
The HTTP Warning header field name. 
See Also:
/**
	 * The HTTP {@code Warning} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7234#section-5.5">Section 5.5 of RFC 7234</a>
	 */
	public static final String WARNING = "Warning";
	
The HTTP WWW-Authenticate header field name. 
See Also:
/**
	 * The HTTP {@code WWW-Authenticate} header field name.
	 * @see <a href="https://tools.ietf.org/html/rfc7235#section-4.1">Section 4.1 of RFC 7235</a>
	 */
	public static final String WWW_AUTHENTICATE = "WWW-Authenticate";


	
An empty HttpHeaders instance (immutable). 
Since:5.0
/**
	 * An empty {@code HttpHeaders} instance (immutable).
	 * @since 5.0
	 */
	public static final HttpHeaders EMPTY = new ReadOnlyHttpHeaders(new LinkedMultiValueMap<>());

	
Pattern matching ETag multiple field values in headers such as "If-Match", "If-None-Match".

See Also:
/**
	 * Pattern matching ETag multiple field values in headers such as "If-Match", "If-None-Match".
	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-2.3">Section 2.3 of RFC 7232</a>
	 */
	private static final Pattern ETAG_HEADER_VALUE_PATTERN = Pattern.compile("\\*|\\s*((W\\/)?(\"[^\"]*\"))\\s*,?");

	private static final DecimalFormatSymbols DECIMAL_FORMAT_SYMBOLS = new DecimalFormatSymbols(Locale.ENGLISH);

	private static final ZoneId GMT = ZoneId.of("GMT");

	
Date formats with time zone as specified in the HTTP RFC to use for formatting.

See Also:
/**
	 * Date formats with time zone as specified in the HTTP RFC to use for formatting.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.1.1">Section 7.1.1.1 of RFC 7231</a>
	 */
	private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US).withZone(GMT);

	
Date formats with time zone as specified in the HTTP RFC to use for parsing.

See Also:
/**
	 * Date formats with time zone as specified in the HTTP RFC to use for parsing.
	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.1.1">Section 7.1.1.1 of RFC 7231</a>
	 */
	private static final DateTimeFormatter[] DATE_PARSERS = new DateTimeFormatter[] {
			DateTimeFormatter.RFC_1123_DATE_TIME,
			DateTimeFormatter.ofPattern("EEEE, dd-MMM-yy HH:mm:ss zzz", Locale.US),
			DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss yyyy", Locale.US).withZone(GMT)
	};


	final MultiValueMap<String, String> headers;


	
Construct a new, empty instance of the HttpHeaders object. 
This is the common constructor, using a case-insensitive map structure.

/**
	 * Construct a new, empty instance of the {@code HttpHeaders} object.
	 * <p>This is the common constructor, using a case-insensitive map structure.
	 */
	public HttpHeaders() {
		this(CollectionUtils.toMultiValueMap(new LinkedCaseInsensitiveMap<>(8, Locale.ENGLISH)));
	}

	
Construct a new HttpHeaders instance backed by an existing map. 
This constructor is available as an optimization for adapting to existing
headers map structures, primarily for internal use within the framework.

Params:
  • headers – the headers map (expected to operate with case-insensitive keys)
Since:5.1
/**
	 * Construct a new {@code HttpHeaders} instance backed by an existing map.
	 * <p>This constructor is available as an optimization for adapting to existing
	 * headers map structures, primarily for internal use within the framework.
	 * @param headers the headers map (expected to operate with case-insensitive keys)
	 * @since 5.1
	 */
	public HttpHeaders(MultiValueMap<String, String> headers) {
		Assert.notNull(headers, "MultiValueMap must not be null");
		this.headers = headers;
	}


	
Get the list of header values for the given header name, if any.

Params:
  • headerName – the header name
Returns:the list of header values, or an empty list
Since:5.2
/**
	 * Get the list of header values for the given header name, if any.
	 * @param headerName the header name
	 * @return the list of header values, or an empty list
	 * @since 5.2
	 */
	public List<String> getOrEmpty(Object headerName) {
		List<String> values = get(headerName);
		return (values != null ? values : Collections.emptyList());
	}

	
Set the list of acceptable media types, as specified by the Accept header. 
/**
	 * Set the list of acceptable {@linkplain MediaType media types},
	 * as specified by the {@code Accept} header.
	 */
	public void setAccept(List<MediaType> acceptableMediaTypes) {
		set(ACCEPT, MediaType.toString(acceptableMediaTypes));
	}

	
Return the list of acceptable media types, as specified by the Accept header. 
Returns an empty list when the acceptable media types are unspecified.

/**
	 * Return the list of acceptable {@linkplain MediaType media types},
	 * as specified by the {@code Accept} header.
	 * <p>Returns an empty list when the acceptable media types are unspecified.
	 */
	public List<MediaType> getAccept() {
		return MediaType.parseMediaTypes(get(ACCEPT));
	}

	
Set the acceptable language ranges, as specified by the Accept-Language header. 
Since:5.0
/**
	 * Set the acceptable language ranges, as specified by the
	 * {@literal Accept-Language} header.
	 * @since 5.0
	 */
	public void setAcceptLanguage(List<Locale.LanguageRange> languages) {
		Assert.notNull(languages, "LanguageRange List must not be null");
		DecimalFormat decimal = new DecimalFormat("0.0", DECIMAL_FORMAT_SYMBOLS);
		List<String> values = languages.stream()
				.map(range ->
						range.getWeight() == Locale.LanguageRange.MAX_WEIGHT ?
								range.getRange() :
								range.getRange() + ";q=" + decimal.format(range.getWeight()))
				.collect(Collectors.toList());
		set(ACCEPT_LANGUAGE, toCommaDelimitedString(values));
	}

	
Return the language ranges from the "Accept-Language" header. 
If you only need sorted, preferred locales only use getAcceptLanguageAsLocales() or if you need to filter based on a list of supported locales you can pass the returned list to Locale.filter(List<LanguageRange>, Collection<Locale>). 
Throws:
Since:5.0
/**
	 * Return the language ranges from the {@literal "Accept-Language"} header.
	 * <p>If you only need sorted, preferred locales only use
	 * {@link #getAcceptLanguageAsLocales()} or if you need to filter based on
	 * a list of supported locales you can pass the returned list to
	 * {@link Locale#filter(List, Collection)}.
	 * @throws IllegalArgumentException if the value cannot be converted to a language range
	 * @since 5.0
	 */
	public List<Locale.LanguageRange> getAcceptLanguage() {
		String value = getFirst(ACCEPT_LANGUAGE);
		return (StringUtils.hasText(value) ? Locale.LanguageRange.parse(value) : Collections.emptyList());
	}

	
Since:5.0
/**
	 * Variant of {@link #setAcceptLanguage(List)} using {@link Locale}'s.
	 * @since 5.0
	 */
	public void setAcceptLanguageAsLocales(List<Locale> locales) {
		setAcceptLanguage(locales.stream()
				.map(locale -> new Locale.LanguageRange(locale.toLanguageTag()))
				.collect(Collectors.toList()));
	}

	
A variant of getAcceptLanguage() that converts each LanguageRange to a Locale. 
Throws:
Returns:the locales or an empty list
Since:5.0
/**
	 * A variant of {@link #getAcceptLanguage()} that converts each
	 * {@link java.util.Locale.LanguageRange} to a {@link Locale}.
	 * @return the locales or an empty list
	 * @throws IllegalArgumentException if the value cannot be converted to a locale
	 * @since 5.0
	 */
	public List<Locale> getAcceptLanguageAsLocales() {
		List<Locale.LanguageRange> ranges = getAcceptLanguage();
		if (ranges.isEmpty()) {
			return Collections.emptyList();
		}
		return ranges.stream()
				.map(range -> Locale.forLanguageTag(range.getRange()))
				.filter(locale -> StringUtils.hasText(locale.getDisplayName()))
				.collect(Collectors.toList());
	}

	
Set the (new) value of the Access-Control-Allow-Credentials response header. 
/**
	 * Set the (new) value of the {@code Access-Control-Allow-Credentials} response header.
	 */
	public void setAccessControlAllowCredentials(boolean allowCredentials) {
		set(ACCESS_CONTROL_ALLOW_CREDENTIALS, Boolean.toString(allowCredentials));
	}

	
Return the value of the Access-Control-Allow-Credentials response header. 
/**
	 * Return the value of the {@code Access-Control-Allow-Credentials} response header.
	 */
	public boolean getAccessControlAllowCredentials() {
		return Boolean.parseBoolean(getFirst(ACCESS_CONTROL_ALLOW_CREDENTIALS));
	}

	
Set the (new) value of the Access-Control-Allow-Headers response header. 
/**
	 * Set the (new) value of the {@code Access-Control-Allow-Headers} response header.
	 */
	public void setAccessControlAllowHeaders(List<String> allowedHeaders) {
		set(ACCESS_CONTROL_ALLOW_HEADERS, toCommaDelimitedString(allowedHeaders));
	}

	
Return the value of the Access-Control-Allow-Headers response header. 
/**
	 * Return the value of the {@code Access-Control-Allow-Headers} response header.
	 */
	public List<String> getAccessControlAllowHeaders() {
		return getValuesAsList(ACCESS_CONTROL_ALLOW_HEADERS);
	}

	
Set the (new) value of the Access-Control-Allow-Methods response header. 
/**
	 * Set the (new) value of the {@code Access-Control-Allow-Methods} response header.
	 */
	public void setAccessControlAllowMethods(List<HttpMethod> allowedMethods) {
		set(ACCESS_CONTROL_ALLOW_METHODS, StringUtils.collectionToCommaDelimitedString(allowedMethods));
	}

	
Return the value of the Access-Control-Allow-Methods response header. 
/**
	 * Return the value of the {@code Access-Control-Allow-Methods} response header.
	 */
	public List<HttpMethod> getAccessControlAllowMethods() {
		List<HttpMethod> result = new ArrayList<>();
		String value = getFirst(ACCESS_CONTROL_ALLOW_METHODS);
		if (value != null) {
			String[] tokens = StringUtils.tokenizeToStringArray(value, ",");
			for (String token : tokens) {
				HttpMethod resolved = HttpMethod.resolve(token);
				if (resolved != null) {
					result.add(resolved);
				}
			}
		}
		return result;
	}

	
Set the (new) value of the Access-Control-Allow-Origin response header. 
/**
	 * Set the (new) value of the {@code Access-Control-Allow-Origin} response header.
	 */
	public void setAccessControlAllowOrigin(@Nullable String allowedOrigin) {
		setOrRemove(ACCESS_CONTROL_ALLOW_ORIGIN, allowedOrigin);
	}

	
Return the value of the Access-Control-Allow-Origin response header. 
/**
	 * Return the value of the {@code Access-Control-Allow-Origin} response header.
	 */
	@Nullable
	public String getAccessControlAllowOrigin() {
		return getFieldValues(ACCESS_CONTROL_ALLOW_ORIGIN);
	}

	
Set the (new) value of the Access-Control-Expose-Headers response header. 
/**
	 * Set the (new) value of the {@code Access-Control-Expose-Headers} response header.
	 */
	public void setAccessControlExposeHeaders(List<String> exposedHeaders) {
		set(ACCESS_CONTROL_EXPOSE_HEADERS, toCommaDelimitedString(exposedHeaders));
	}

	
Return the value of the Access-Control-Expose-Headers response header. 
/**
	 * Return the value of the {@code Access-Control-Expose-Headers} response header.
	 */
	public List<String> getAccessControlExposeHeaders() {
		return getValuesAsList(ACCESS_CONTROL_EXPOSE_HEADERS);
	}

	
Set the (new) value of the Access-Control-Max-Age response header. 
Since:5.2
/**
	 * Set the (new) value of the {@code Access-Control-Max-Age} response header.
	 * @since 5.2
	 */
	public void setAccessControlMaxAge(Duration maxAge) {
		set(ACCESS_CONTROL_MAX_AGE, Long.toString(maxAge.getSeconds()));
	}

	
Set the (new) value of the Access-Control-Max-Age response header. 
/**
	 * Set the (new) value of the {@code Access-Control-Max-Age} response header.
	 */
	public void setAccessControlMaxAge(long maxAge) {
		set(ACCESS_CONTROL_MAX_AGE, Long.toString(maxAge));
	}

	
Return the value of the Access-Control-Max-Age response header. 
Returns -1 when the max age is unknown.

/**
	 * Return the value of the {@code Access-Control-Max-Age} response header.
	 * <p>Returns -1 when the max age is unknown.
	 */
	public long getAccessControlMaxAge() {
		String value = getFirst(ACCESS_CONTROL_MAX_AGE);
		return (value != null ? Long.parseLong(value) : -1);
	}

	
Set the (new) value of the Access-Control-Request-Headers request header. 
/**
	 * Set the (new) value of the {@code Access-Control-Request-Headers} request header.
	 */
	public void setAccessControlRequestHeaders(List<String> requestHeaders) {
		set(ACCESS_CONTROL_REQUEST_HEADERS, toCommaDelimitedString(requestHeaders));
	}

	
Return the value of the Access-Control-Request-Headers request header. 
/**
	 * Return the value of the {@code Access-Control-Request-Headers} request header.
	 */
	public List<String> getAccessControlRequestHeaders() {
		return getValuesAsList(ACCESS_CONTROL_REQUEST_HEADERS);
	}

	
Set the (new) value of the Access-Control-Request-Method request header. 
/**
	 * Set the (new) value of the {@code Access-Control-Request-Method} request header.
	 */
	public void setAccessControlRequestMethod(@Nullable HttpMethod requestMethod) {
		setOrRemove(ACCESS_CONTROL_REQUEST_METHOD, (requestMethod != null ? requestMethod.name() : null));
	}

	
Return the value of the Access-Control-Request-Method request header. 
/**
	 * Return the value of the {@code Access-Control-Request-Method} request header.
	 */
	@Nullable
	public HttpMethod getAccessControlRequestMethod() {
		return HttpMethod.resolve(getFirst(ACCESS_CONTROL_REQUEST_METHOD));
	}

	
Set the list of acceptable charsets, as specified by the Accept-Charset header. 
/**
	 * Set the list of acceptable {@linkplain Charset charsets},
	 * as specified by the {@code Accept-Charset} header.
	 */
	public void setAcceptCharset(List<Charset> acceptableCharsets) {
		StringJoiner joiner = new StringJoiner(", ");
		for (Charset charset : acceptableCharsets) {
			joiner.add(charset.name().toLowerCase(Locale.ENGLISH));
		}
		set(ACCEPT_CHARSET, joiner.toString());
	}

	
Return the list of acceptable charsets, as specified by the Accept-Charset header. 
/**
	 * Return the list of acceptable {@linkplain Charset charsets},
	 * as specified by the {@code Accept-Charset} header.
	 */
	public List<Charset> getAcceptCharset() {
		String value = getFirst(ACCEPT_CHARSET);
		if (value != null) {
			String[] tokens = StringUtils.tokenizeToStringArray(value, ",");
			List<Charset> result = new ArrayList<>(tokens.length);
			for (String token : tokens) {
				int paramIdx = token.indexOf(';');
				String charsetName;
				if (paramIdx == -1) {
					charsetName = token;
				}
				else {
					charsetName = token.substring(0, paramIdx);
				}
				if (!charsetName.equals("*")) {
					result.add(Charset.forName(charsetName));
				}
			}
			return result;
		}
		else {
			return Collections.emptyList();
		}
	}

	
Set the set of allowed HTTP methods, as specified by the Allow header. 
/**
	 * Set the set of allowed {@link HttpMethod HTTP methods},
	 * as specified by the {@code Allow} header.
	 */
	public void setAllow(Set<HttpMethod> allowedMethods) {
		set(ALLOW, StringUtils.collectionToCommaDelimitedString(allowedMethods));
	}

	
Return the set of allowed HTTP methods, as specified by the Allow header. 
Returns an empty set when the allowed methods are unspecified.

/**
	 * Return the set of allowed {@link HttpMethod HTTP methods},
	 * as specified by the {@code Allow} header.
	 * <p>Returns an empty set when the allowed methods are unspecified.
	 */
	public Set<HttpMethod> getAllow() {
		String value = getFirst(ALLOW);
		if (StringUtils.hasLength(value)) {
			String[] tokens = StringUtils.tokenizeToStringArray(value, ",");
			List<HttpMethod> result = new ArrayList<>(tokens.length);
			for (String token : tokens) {
				HttpMethod resolved = HttpMethod.resolve(token);
				if (resolved != null) {
					result.add(resolved);
				}
			}
			return EnumSet.copyOf(result);
		}
		else {
			return EnumSet.noneOf(HttpMethod.class);
		}
	}

	
Set the value of the Authorization header to Basic Authentication based on the given username and password. 
Note that this method only supports characters in the ISO-8859-1 character set. 
Params:
  • username – the username
  • password – the password
Throws:
See Also:
Since:5.1
/**
	 * Set the value of the {@linkplain #AUTHORIZATION Authorization} header to
	 * Basic Authentication based on the given username and password.
	 * <p>Note that this method only supports characters in the
	 * {@link StandardCharsets#ISO_8859_1 ISO-8859-1} character set.
	 * @param username the username
	 * @param password the password
	 * @throws IllegalArgumentException if either {@code user} or
	 * {@code password} contain characters that cannot be encoded to ISO-8859-1
	 * @since 5.1
	 * @see #setBasicAuth(String)
	 * @see #setBasicAuth(String, String, Charset)
	 * @see #encodeBasicAuth(String, String, Charset)
	 * @see <a href="https://tools.ietf.org/html/rfc7617">RFC 7617</a>
	 */
	public void setBasicAuth(String username, String password) {
		setBasicAuth(username, password, null);
	}

	
Set the value of the Authorization header to Basic Authentication based on the given username and password. 
Params:
  • username – the username
  • password – the password
  • charset – the charset to use to convert the credentials into an octet sequence. Defaults to ISO-8859-1.
Throws:
See Also:
Since:5.1
/**
	 * Set the value of the {@linkplain #AUTHORIZATION Authorization} header to
	 * Basic Authentication based on the given username and password.
	 * @param username the username
	 * @param password the password
	 * @param charset the charset to use to convert the credentials into an octet
	 * sequence. Defaults to {@linkplain StandardCharsets#ISO_8859_1 ISO-8859-1}.
	 * @throws IllegalArgumentException if {@code username} or {@code password}
	 * contains characters that cannot be encoded to the given charset
	 * @since 5.1
	 * @see #setBasicAuth(String)
	 * @see #setBasicAuth(String, String)
	 * @see #encodeBasicAuth(String, String, Charset)
	 * @see <a href="https://tools.ietf.org/html/rfc7617">RFC 7617</a>
	 */
	public void setBasicAuth(String username, String password, @Nullable Charset charset) {
		setBasicAuth(encodeBasicAuth(username, password, charset));
	}

	
Set the value of the Authorization header to Basic Authentication based on the given 
encoded credentials. 
Favor this method over setBasicAuth(String, String) and setBasicAuth(String, String, Charset) if you wish to cache the encoded credentials. 
Params:
  • encodedCredentials – the encoded credentials
Throws:
See Also:
Since:5.2
/**
	 * Set the value of the {@linkplain #AUTHORIZATION Authorization} header to
	 * Basic Authentication based on the given {@linkplain #encodeBasicAuth
	 * encoded credentials}.
	 * <p>Favor this method over {@link #setBasicAuth(String, String)} and
	 * {@link #setBasicAuth(String, String, Charset)} if you wish to cache the
	 * encoded credentials.
	 * @param encodedCredentials the encoded credentials
	 * @throws IllegalArgumentException if supplied credentials string is
	 * {@code null} or blank
	 * @since 5.2
	 * @see #setBasicAuth(String, String)
	 * @see #setBasicAuth(String, String, Charset)
	 * @see #encodeBasicAuth(String, String, Charset)
	 * @see <a href="https://tools.ietf.org/html/rfc7617">RFC 7617</a>
	 */
	public void setBasicAuth(String encodedCredentials) {
		Assert.hasText(encodedCredentials, "'encodedCredentials' must not be null or blank");
		set(AUTHORIZATION, "Basic " + encodedCredentials);
	}

	
Set the value of the Authorization header to the given Bearer token. 
Params:
  • token – the Base64 encoded token
See Also:
Since:5.1
/**
	 * Set the value of the {@linkplain #AUTHORIZATION Authorization} header to
	 * the given Bearer token.
	 * @param token the Base64 encoded token
	 * @since 5.1
	 * @see <a href="https://tools.ietf.org/html/rfc6750">RFC 6750</a>
	 */
	public void setBearerAuth(String token) {
		set(AUTHORIZATION, "Bearer " + token);
	}

	
Set a configured CacheControl instance as the new value of the Cache-Control header. 
Since:5.0.5
/**
	 * Set a configured {@link CacheControl} instance as the
	 * new value of the {@code Cache-Control} header.
	 * @since 5.0.5
	 */
	public void setCacheControl(CacheControl cacheControl) {
		setOrRemove(CACHE_CONTROL, cacheControl.getHeaderValue());
	}

	
Set the (new) value of the Cache-Control header. 
/**
	 * Set the (new) value of the {@code Cache-Control} header.
	 */
	public void setCacheControl(@Nullable String cacheControl) {
		setOrRemove(CACHE_CONTROL, cacheControl);
	}

	
Return the value of the Cache-Control header. 
/**
	 * Return the value of the {@code Cache-Control} header.
	 */
	@Nullable
	public String getCacheControl() {
		return getFieldValues(CACHE_CONTROL);
	}

	
Set the (new) value of the Connection header. 
/**
	 * Set the (new) value of the {@code Connection} header.
	 */
	public void setConnection(String connection) {
		set(CONNECTION, connection);
	}

	
Set the (new) value of the Connection header. 
/**
	 * Set the (new) value of the {@code Connection} header.
	 */
	public void setConnection(List<String> connection) {
		set(CONNECTION, toCommaDelimitedString(connection));
	}

	
Return the value of the Connection header. 
/**
	 * Return the value of the {@code Connection} header.
	 */
	public List<String> getConnection() {
		return getValuesAsList(CONNECTION);
	}

	
Set the Content-Disposition header when creating a "multipart/form-data" request. 
Applications typically would not set this header directly but rather prepare a MultiValueMap<String, Object>, containing an Object or a Resource for each part, and then pass that to the RestTemplate or WebClient. 
Params:
  • name – the control name
  • filename – the filename (may be null)
See Also:
/**
	 * Set the {@code Content-Disposition} header when creating a
	 * {@code "multipart/form-data"} request.
	 * <p>Applications typically would not set this header directly but
	 * rather prepare a {@code MultiValueMap<String, Object>}, containing an
	 * Object or a {@link org.springframework.core.io.Resource} for each part,
	 * and then pass that to the {@code RestTemplate} or {@code WebClient}.
	 * @param name the control name
	 * @param filename the filename (may be {@code null})
	 * @see #getContentDisposition()
	 */
	public void setContentDispositionFormData(String name, @Nullable String filename) {
		Assert.notNull(name, "Name must not be null");
		ContentDisposition.Builder disposition = ContentDisposition.formData().name(name);
		if (StringUtils.hasText(filename)) {
			disposition.filename(filename);
		}
		setContentDisposition(disposition.build());
	}

	
Set the Content-Disposition header. 
This could be used on a response to indicate if the content is
expected to be displayed inline in the browser or as an attachment to be
saved locally.

It can also be used for a "multipart/form-data" request. For more details see notes on setContentDispositionFormData. 
See Also:
Since:5.0
/**
	 * Set the {@literal Content-Disposition} header.
	 * <p>This could be used on a response to indicate if the content is
	 * expected to be displayed inline in the browser or as an attachment to be
	 * saved locally.
	 * <p>It can also be used for a {@code "multipart/form-data"} request.
	 * For more details see notes on {@link #setContentDispositionFormData}.
	 * @since 5.0
	 * @see #getContentDisposition()
	 */
	public void setContentDisposition(ContentDisposition contentDisposition) {
		set(CONTENT_DISPOSITION, contentDisposition.toString());
	}

	
Return a parsed representation of the Content-Disposition header. 
See Also:
Since:5.0
/**
	 * Return a parsed representation of the {@literal Content-Disposition} header.
	 * @since 5.0
	 * @see #setContentDisposition(ContentDisposition)
	 */
	public ContentDisposition getContentDisposition() {
		String contentDisposition = getFirst(CONTENT_DISPOSITION);
		if (StringUtils.hasText(contentDisposition)) {
			return ContentDisposition.parse(contentDisposition);
		}
		return ContentDisposition.empty();
	}

	
Set the Locale of the content language, as specified by the Content-Language header. 
Use put(CONTENT_LANGUAGE, list) if you need to set multiple content languages.


Since:5.0
/**
	 * Set the {@link Locale} of the content language,
	 * as specified by the {@literal Content-Language} header.
	 * <p>Use {@code put(CONTENT_LANGUAGE, list)} if you need
	 * to set multiple content languages.</p>
	 * @since 5.0
	 */
	public void setContentLanguage(@Nullable Locale locale) {
		setOrRemove(CONTENT_LANGUAGE, (locale != null ? locale.toLanguageTag() : null));
	}

	
Get the first Locale of the content languages, as specified by the Content-Language header. 
Use getValuesAsList(String) if you need to get multiple content languages. 
Returns:the first Locale of the content languages, or null if unknown
Since:5.0
/**
	 * Get the first {@link Locale} of the content languages, as specified by the
	 * {@code Content-Language} header.
	 * <p>Use {@link #getValuesAsList(String)} if you need to get multiple content
	 * languages.
	 * @return the first {@code Locale} of the content languages, or {@code null}
	 * if unknown
	 * @since 5.0
	 */
	@Nullable
	public Locale getContentLanguage() {
		return getValuesAsList(CONTENT_LANGUAGE)
				.stream()
				.findFirst()
				.map(Locale::forLanguageTag)
				.orElse(null);
	}

	
Set the length of the body in bytes, as specified by the Content-Length header. 
/**
	 * Set the length of the body in bytes, as specified by the
	 * {@code Content-Length} header.
	 */
	public void setContentLength(long contentLength) {
		set(CONTENT_LENGTH, Long.toString(contentLength));
	}

	
Return the length of the body in bytes, as specified by the Content-Length header. 
Returns -1 when the content-length is unknown.

/**
	 * Return the length of the body in bytes, as specified by the
	 * {@code Content-Length} header.
	 * <p>Returns -1 when the content-length is unknown.
	 */
	public long getContentLength() {
		String value = getFirst(CONTENT_LENGTH);
		return (value != null ? Long.parseLong(value) : -1);
	}

	
Set the media type of the body, as specified by the Content-Type header. 
/**
	 * Set the {@linkplain MediaType media type} of the body,
	 * as specified by the {@code Content-Type} header.
	 */
	public void setContentType(@Nullable MediaType mediaType) {
		if (mediaType != null) {
			Assert.isTrue(!mediaType.isWildcardType(), "Content-Type cannot contain wildcard type '*'");
			Assert.isTrue(!mediaType.isWildcardSubtype(), "Content-Type cannot contain wildcard subtype '*'");
			set(CONTENT_TYPE, mediaType.toString());
		}
		else {
			remove(CONTENT_TYPE);
		}
	}

	
Return the media type of the body, as specified by the Content-Type header. 
Returns null when the content-type is unknown. 
/**
	 * Return the {@linkplain MediaType media type} of the body, as specified
	 * by the {@code Content-Type} header.
	 * <p>Returns {@code null} when the content-type is unknown.
	 */
	@Nullable
	public MediaType getContentType() {
		String value = getFirst(CONTENT_TYPE);
		return (StringUtils.hasLength(value) ? MediaType.parseMediaType(value) : null);
	}

	
Set the date and time at which the message was created, as specified by the Date header. 
Since:5.2
/**
	 * Set the date and time at which the message was created, as specified
	 * by the {@code Date} header.
	 * @since 5.2
	 */
	public void setDate(ZonedDateTime date) {
		setZonedDateTime(DATE, date);
	}

	
Set the date and time at which the message was created, as specified by the Date header. 
Since:5.2
/**
	 * Set the date and time at which the message was created, as specified
	 * by the {@code Date} header.
	 * @since 5.2
	 */
	public void setDate(Instant date) {
		setInstant(DATE, date);
	}

	
Set the date and time at which the message was created, as specified by the Date header. 
The date should be specified as the number of milliseconds since
January 1, 1970 GMT.

/**
	 * Set the date and time at which the message was created, as specified
	 * by the {@code Date} header.
	 * <p>The date should be specified as the number of milliseconds since
	 * January 1, 1970 GMT.
	 */
	public void setDate(long date) {
		setDate(DATE, date);
	}

	
Return the date and time at which the message was created, as specified by the Date header. 
The date is returned as the number of milliseconds since
January 1, 1970 GMT. Returns -1 when the date is unknown.

Throws:
/**
	 * Return the date and time at which the message was created, as specified
	 * by the {@code Date} header.
	 * <p>The date is returned as the number of milliseconds since
	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
	 * @throws IllegalArgumentException if the value cannot be converted to a date
	 */
	public long getDate() {
		return getFirstDate(DATE);
	}

	
Set the (new) entity tag of the body, as specified by the ETag header. 
/**
	 * Set the (new) entity tag of the body, as specified by the {@code ETag} header.
	 */
	public void setETag(@Nullable String etag) {
		if (etag != null) {
			Assert.isTrue(etag.startsWith("\"") || etag.startsWith("W/"),
					"Invalid ETag: does not start with W/ or \"");
			Assert.isTrue(etag.endsWith("\""), "Invalid ETag: does not end with \"");
			set(ETAG, etag);
		}
		else {
			remove(ETAG);
		}
	}

	
Return the entity tag of the body, as specified by the ETag header. 
/**
	 * Return the entity tag of the body, as specified by the {@code ETag} header.
	 */
	@Nullable
	public String getETag() {
		return getFirst(ETAG);
	}

	
Set the duration after which the message is no longer valid, as specified by the Expires header. 
Since:5.0.5
/**
	 * Set the duration after which the message is no longer valid,
	 * as specified by the {@code Expires} header.
	 * @since 5.0.5
	 */
	public void setExpires(ZonedDateTime expires) {
		setZonedDateTime(EXPIRES, expires);
	}

	
Set the date and time at which the message is no longer valid, as specified by the Expires header. 
Since:5.2
/**
	 * Set the date and time at which the message is no longer valid,
	 * as specified by the {@code Expires} header.
	 * @since 5.2
	 */
	public void setExpires(Instant expires) {
		setInstant(EXPIRES, expires);
	}

	
Set the date and time at which the message is no longer valid, as specified by the Expires header. 
The date should be specified as the number of milliseconds since
January 1, 1970 GMT.

/**
	 * Set the date and time at which the message is no longer valid,
	 * as specified by the {@code Expires} header.
	 * <p>The date should be specified as the number of milliseconds since
	 * January 1, 1970 GMT.
	 */
	public void setExpires(long expires) {
		setDate(EXPIRES, expires);
	}

	
Return the date and time at which the message is no longer valid, as specified by the Expires header. 
The date is returned as the number of milliseconds since
January 1, 1970 GMT. Returns -1 when the date is unknown.

See Also:
/**
	 * Return the date and time at which the message is no longer valid,
	 * as specified by the {@code Expires} header.
	 * <p>The date is returned as the number of milliseconds since
	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
	 * @see #getFirstZonedDateTime(String)
	 */
	public long getExpires() {
		return getFirstDate(EXPIRES, false);
	}

	
Set the (new) value of the Host header. 
If the given port is 0, the host header will only contain the host name. 
Since:5.0
/**
	 * Set the (new) value of the {@code Host} header.
	 * <p>If the given {@linkplain InetSocketAddress#getPort() port} is {@code 0},
	 * the host header will only contain the
	 * {@linkplain InetSocketAddress#getHostString() host name}.
	 * @since 5.0
	 */
	public void setHost(@Nullable InetSocketAddress host) {
		if (host != null) {
			String value = host.getHostString();
			int port = host.getPort();
			if (port != 0) {
				value = value + ":" + port;
			}
			set(HOST, value);
		}
		else {
			remove(HOST, null);
		}
	}

	
Return the value of the Host header, if available. 
If the header value does not contain a port, the port in the returned address will be 0. 
Since:5.0
/**
	 * Return the value of the {@code Host} header, if available.
	 * <p>If the header value does not contain a port, the
	 * {@linkplain InetSocketAddress#getPort() port} in the returned address will
	 * be {@code 0}.
	 * @since 5.0
	 */
	@Nullable
	public InetSocketAddress getHost() {
		String value = getFirst(HOST);
		if (value == null) {
			return null;
		}

		String host = null;
		int port = 0;
		int separator = (value.startsWith("[") ? value.indexOf(':', value.indexOf(']')) : value.lastIndexOf(':'));
		if (separator != -1) {
			host = value.substring(0, separator);
			String portString = value.substring(separator + 1);
			try {
				port = Integer.parseInt(portString);
			}
			catch (NumberFormatException ex) {
				// ignore
			}
		}

		if (host == null) {
			host = value;
		}
		return InetSocketAddress.createUnresolved(host, port);
	}

	
Set the (new) value of the If-Match header. 
Since:4.3
/**
	 * Set the (new) value of the {@code If-Match} header.
	 * @since 4.3
	 */
	public void setIfMatch(String ifMatch) {
		set(IF_MATCH, ifMatch);
	}

	
Set the (new) value of the If-Match header. 
Since:4.3
/**
	 * Set the (new) value of the {@code If-Match} header.
	 * @since 4.3
	 */
	public void setIfMatch(List<String> ifMatchList) {
		set(IF_MATCH, toCommaDelimitedString(ifMatchList));
	}

	
Return the value of the If-Match header. 
Throws:
Since:4.3
/**
	 * Return the value of the {@code If-Match} header.
	 * @throws IllegalArgumentException if parsing fails
	 * @since 4.3
	 */
	public List<String> getIfMatch() {
		return getETagValuesAsList(IF_MATCH);
	}

	
Set the time the resource was last changed, as specified by the Last-Modified header. 
Since:5.1.4
/**
	 * Set the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * @since 5.1.4
	 */
	public void setIfModifiedSince(ZonedDateTime ifModifiedSince) {
		setZonedDateTime(IF_MODIFIED_SINCE, ifModifiedSince.withZoneSameInstant(GMT));
	}

	
Set the time the resource was last changed, as specified by the Last-Modified header. 
Since:5.1.4
/**
	 * Set the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * @since 5.1.4
	 */
	public void setIfModifiedSince(Instant ifModifiedSince) {
		setInstant(IF_MODIFIED_SINCE, ifModifiedSince);
	}

	
Set the (new) value of the If-Modified-Since header. 
The date should be specified as the number of milliseconds since
January 1, 1970 GMT.

/**
	 * Set the (new) value of the {@code If-Modified-Since} header.
	 * <p>The date should be specified as the number of milliseconds since
	 * January 1, 1970 GMT.
	 */
	public void setIfModifiedSince(long ifModifiedSince) {
		setDate(IF_MODIFIED_SINCE, ifModifiedSince);
	}

	
Return the value of the If-Modified-Since header. 
The date is returned as the number of milliseconds since
January 1, 1970 GMT. Returns -1 when the date is unknown.

See Also:
/**
	 * Return the value of the {@code If-Modified-Since} header.
	 * <p>The date is returned as the number of milliseconds since
	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
	 * @see #getFirstZonedDateTime(String)
	 */
	public long getIfModifiedSince() {
		return getFirstDate(IF_MODIFIED_SINCE, false);
	}

	
Set the (new) value of the If-None-Match header. 
/**
	 * Set the (new) value of the {@code If-None-Match} header.
	 */
	public void setIfNoneMatch(String ifNoneMatch) {
		set(IF_NONE_MATCH, ifNoneMatch);
	}

	
Set the (new) values of the If-None-Match header. 
/**
	 * Set the (new) values of the {@code If-None-Match} header.
	 */
	public void setIfNoneMatch(List<String> ifNoneMatchList) {
		set(IF_NONE_MATCH, toCommaDelimitedString(ifNoneMatchList));
	}

	
Return the value of the If-None-Match header. 
Throws:
/**
	 * Return the value of the {@code If-None-Match} header.
	 * @throws IllegalArgumentException if parsing fails
	 */
	public List<String> getIfNoneMatch() {
		return getETagValuesAsList(IF_NONE_MATCH);
	}

	
Set the time the resource was last changed, as specified by the Last-Modified header. 
Since:5.1.4
/**
	 * Set the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * @since 5.1.4
	 */
	public void setIfUnmodifiedSince(ZonedDateTime ifUnmodifiedSince) {
		setZonedDateTime(IF_UNMODIFIED_SINCE, ifUnmodifiedSince.withZoneSameInstant(GMT));
	}

	
Set the time the resource was last changed, as specified by the Last-Modified header. 
Since:5.1.4
/**
	 * Set the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * @since 5.1.4
	 */
	public void setIfUnmodifiedSince(Instant ifUnmodifiedSince) {
		setInstant(IF_UNMODIFIED_SINCE, ifUnmodifiedSince);
	}

	
Set the (new) value of the If-Unmodified-Since header. 
The date should be specified as the number of milliseconds since
January 1, 1970 GMT.

Since:4.3
/**
	 * Set the (new) value of the {@code If-Unmodified-Since} header.
	 * <p>The date should be specified as the number of milliseconds since
	 * January 1, 1970 GMT.
	 * @since 4.3
	 */
	public void setIfUnmodifiedSince(long ifUnmodifiedSince) {
		setDate(IF_UNMODIFIED_SINCE, ifUnmodifiedSince);
	}

	
Return the value of the If-Unmodified-Since header. 
The date is returned as the number of milliseconds since
January 1, 1970 GMT. Returns -1 when the date is unknown.

See Also:
Since:4.3
/**
	 * Return the value of the {@code If-Unmodified-Since} header.
	 * <p>The date is returned as the number of milliseconds since
	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
	 * @since 4.3
	 * @see #getFirstZonedDateTime(String)
	 */
	public long getIfUnmodifiedSince() {
		return getFirstDate(IF_UNMODIFIED_SINCE, false);
	}

	
Set the time the resource was last changed, as specified by the Last-Modified header. 
Since:5.1.4
/**
	 * Set the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * @since 5.1.4
	 */
	public void setLastModified(ZonedDateTime lastModified) {
		setZonedDateTime(LAST_MODIFIED, lastModified.withZoneSameInstant(GMT));
	}

	
Set the time the resource was last changed, as specified by the Last-Modified header. 
Since:5.1.4
/**
	 * Set the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * @since 5.1.4
	 */
	public void setLastModified(Instant lastModified) {
		setInstant(LAST_MODIFIED, lastModified);
	}

	
Set the time the resource was last changed, as specified by the Last-Modified header. 
The date should be specified as the number of milliseconds since
January 1, 1970 GMT.

/**
	 * Set the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * <p>The date should be specified as the number of milliseconds since
	 * January 1, 1970 GMT.
	 */
	public void setLastModified(long lastModified) {
		setDate(LAST_MODIFIED, lastModified);
	}

	
Return the time the resource was last changed, as specified by the Last-Modified header. 
The date is returned as the number of milliseconds since
January 1, 1970 GMT. Returns -1 when the date is unknown.

See Also:
/**
	 * Return the time the resource was last changed, as specified by the
	 * {@code Last-Modified} header.
	 * <p>The date is returned as the number of milliseconds since
	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
	 * @see #getFirstZonedDateTime(String)
	 */
	public long getLastModified() {
		return getFirstDate(LAST_MODIFIED, false);
	}

	
Set the (new) location of a resource, as specified by the Location header. 
/**
	 * Set the (new) location of a resource,
	 * as specified by the {@code Location} header.
	 */
	public void setLocation(@Nullable URI location) {
		setOrRemove(LOCATION, (location != null ? location.toASCIIString() : null));
	}

	
Return the (new) location of a resource as specified by the Location header. 
Returns null when the location is unknown. 
/**
	 * Return the (new) location of a resource
	 * as specified by the {@code Location} header.
	 * <p>Returns {@code null} when the location is unknown.
	 */
	@Nullable
	public URI getLocation() {
		String value = getFirst(LOCATION);
		return (value != null ? URI.create(value) : null);
	}

	
Set the (new) value of the Origin header. 
/**
	 * Set the (new) value of the {@code Origin} header.
	 */
	public void setOrigin(@Nullable String origin) {
		setOrRemove(ORIGIN, origin);
	}

	
Return the value of the Origin header. 
/**
	 * Return the value of the {@code Origin} header.
	 */
	@Nullable
	public String getOrigin() {
		return getFirst(ORIGIN);
	}

	
Set the (new) value of the Pragma header. 
/**
	 * Set the (new) value of the {@code Pragma} header.
	 */
	public void setPragma(@Nullable String pragma) {
		setOrRemove(PRAGMA, pragma);
	}

	
Return the value of the Pragma header. 
/**
	 * Return the value of the {@code Pragma} header.
	 */
	@Nullable
	public String getPragma() {
		return getFirst(PRAGMA);
	}

	
Sets the (new) value of the Range header. 
/**
	 * Sets the (new) value of the {@code Range} header.
	 */
	public void setRange(List<HttpRange> ranges) {
		String value = HttpRange.toString(ranges);
		set(RANGE, value);
	}

	
Return the value of the Range header. 
Returns an empty list when the range is unknown.

/**
	 * Return the value of the {@code Range} header.
	 * <p>Returns an empty list when the range is unknown.
	 */
	public List<HttpRange> getRange() {
		String value = getFirst(RANGE);
		return HttpRange.parseRanges(value);
	}

	
Set the (new) value of the Upgrade header. 
/**
	 * Set the (new) value of the {@code Upgrade} header.
	 */
	public void setUpgrade(@Nullable String upgrade) {
		setOrRemove(UPGRADE, upgrade);
	}

	
Return the value of the Upgrade header. 
/**
	 * Return the value of the {@code Upgrade} header.
	 */
	@Nullable
	public String getUpgrade() {
		return getFirst(UPGRADE);
	}

	
Set the request header names (e.g. "Accept-Language") for which the
response is subject to content negotiation and variances based on the
value of those request headers.

Params:
  • requestHeaders – the request header names
Since:4.3
/**
	 * Set the request header names (e.g. "Accept-Language") for which the
	 * response is subject to content negotiation and variances based on the
	 * value of those request headers.
	 * @param requestHeaders the request header names
	 * @since 4.3
	 */
	public void setVary(List<String> requestHeaders) {
		set(VARY, toCommaDelimitedString(requestHeaders));
	}

	
Return the request header names subject to content negotiation.

Since:4.3
/**
	 * Return the request header names subject to content negotiation.
	 * @since 4.3
	 */
	public List<String> getVary() {
		return getValuesAsList(VARY);
	}

	
Set the given date under the given header name after formatting it as a string using the RFC-1123 date-time formatter. The equivalent of set(String, String) but for date headers. 
Since:5.0
/**
	 * Set the given date under the given header name after formatting it as a string
	 * using the RFC-1123 date-time formatter. The equivalent of
	 * {@link #set(String, String)} but for date headers.
	 * @since 5.0
	 */
	public void setZonedDateTime(String headerName, ZonedDateTime date) {
		set(headerName, DATE_FORMATTER.format(date));
	}

	
Set the given date under the given header name after formatting it as a string using the RFC-1123 date-time formatter. The equivalent of set(String, String) but for date headers. 
Since:5.1.4
/**
	 * Set the given date under the given header name after formatting it as a string
	 * using the RFC-1123 date-time formatter. The equivalent of
	 * {@link #set(String, String)} but for date headers.
	 * @since 5.1.4
	 */
	public void setInstant(String headerName, Instant date) {
		setZonedDateTime(headerName, ZonedDateTime.ofInstant(date, GMT));
	}

	
Set the given date under the given header name after formatting it as a string using the RFC-1123 date-time formatter. The equivalent of set(String, String) but for date headers. 
See Also:
Since:3.2.4
/**
	 * Set the given date under the given header name after formatting it as a string
	 * using the RFC-1123 date-time formatter. The equivalent of
	 * {@link #set(String, String)} but for date headers.
	 * @since 3.2.4
	 * @see #setZonedDateTime(String, ZonedDateTime)
	 */
	public void setDate(String headerName, long date) {
		setInstant(headerName, Instant.ofEpochMilli(date));
	}

	
Parse the first header value for the given header name as a date, return -1 if there is no value, or raise IllegalArgumentException if the value cannot be parsed as a date. 
Params:
  • headerName – the header name
See Also:
Returns:the parsed date header, or -1 if none
Since:3.2.4
/**
	 * Parse the first header value for the given header name as a date,
	 * return -1 if there is no value, or raise {@link IllegalArgumentException}
	 * if the value cannot be parsed as a date.
	 * @param headerName the header name
	 * @return the parsed date header, or -1 if none
	 * @since 3.2.4
	 * @see #getFirstZonedDateTime(String)
	 */
	public long getFirstDate(String headerName) {
		return getFirstDate(headerName, true);
	}

	
Parse the first header value for the given header name as a date, return -1 if there is no value or also in case of an invalid value (if rejectInvalid=false), or raise IllegalArgumentException if the value cannot be parsed as a date. 
Params:
  • headerName – the header name
  • rejectInvalid – whether to reject invalid values with an IllegalArgumentException (true) or rather return -1 in that case (false)
See Also:
Returns:the parsed date header, or -1 if none (or invalid)
/**
	 * Parse the first header value for the given header name as a date,
	 * return -1 if there is no value or also in case of an invalid value
	 * (if {@code rejectInvalid=false}), or raise {@link IllegalArgumentException}
	 * if the value cannot be parsed as a date.
	 * @param headerName the header name
	 * @param rejectInvalid whether to reject invalid values with an
	 * {@link IllegalArgumentException} ({@code true}) or rather return -1
	 * in that case ({@code false})
	 * @return the parsed date header, or -1 if none (or invalid)
	 * @see #getFirstZonedDateTime(String, boolean)
	 */
	private long getFirstDate(String headerName, boolean rejectInvalid) {
		ZonedDateTime zonedDateTime = getFirstZonedDateTime(headerName, rejectInvalid);
		return (zonedDateTime != null ? zonedDateTime.toInstant().toEpochMilli() : -1);
	}

	
Parse the first header value for the given header name as a date, return null if there is no value, or raise IllegalArgumentException if the value cannot be parsed as a date. 
Params:
  • headerName – the header name
Returns:the parsed date header, or null if none
Since:5.0
/**
	 * Parse the first header value for the given header name as a date,
	 * return {@code null} if there is no value, or raise {@link IllegalArgumentException}
	 * if the value cannot be parsed as a date.
	 * @param headerName the header name
	 * @return the parsed date header, or {@code null} if none
	 * @since 5.0
	 */
	@Nullable
	public ZonedDateTime getFirstZonedDateTime(String headerName) {
		return getFirstZonedDateTime(headerName, true);
	}

	
Parse the first header value for the given header name as a date, return null if there is no value or also in case of an invalid value (if rejectInvalid=false), or raise IllegalArgumentException if the value cannot be parsed as a date. 
Params:
  • headerName – the header name
  • rejectInvalid – whether to reject invalid values with an IllegalArgumentException (true) or rather return null in that case (false)
Returns:the parsed date header, or null if none (or invalid)
/**
	 * Parse the first header value for the given header name as a date,
	 * return {@code null} if there is no value or also in case of an invalid value
	 * (if {@code rejectInvalid=false}), or raise {@link IllegalArgumentException}
	 * if the value cannot be parsed as a date.
	 * @param headerName the header name
	 * @param rejectInvalid whether to reject invalid values with an
	 * {@link IllegalArgumentException} ({@code true}) or rather return {@code null}
	 * in that case ({@code false})
	 * @return the parsed date header, or {@code null} if none (or invalid)
	 */
	@Nullable
	private ZonedDateTime getFirstZonedDateTime(String headerName, boolean rejectInvalid) {
		String headerValue = getFirst(headerName);
		if (headerValue == null) {
			// No header value sent at all
			return null;
		}
		if (headerValue.length() >= 3) {
			// Short "0" or "-1" like values are never valid HTTP date headers...
			// Let's only bother with DateTimeFormatter parsing for long enough values.

			// See https://stackoverflow.com/questions/12626699/if-modified-since-http-header-passed-by-ie9-includes-length
			int parametersIndex = headerValue.indexOf(';');
			if (parametersIndex != -1) {
				headerValue = headerValue.substring(0, parametersIndex);
			}

			for (DateTimeFormatter dateFormatter : DATE_PARSERS) {
				try {
					return ZonedDateTime.parse(headerValue, dateFormatter);
				}
				catch (DateTimeParseException ex) {
					// ignore
				}
			}

		}
		if (rejectInvalid) {
			throw new IllegalArgumentException("Cannot parse date value \"" + headerValue +
					"\" for \"" + headerName + "\" header");
		}
		return null;
	}

	
Return all values of a given header name,
even if this header is set multiple times.

Params:
  • headerName – the header name
Returns:all associated values
Since:4.3
/**
	 * Return all values of a given header name,
	 * even if this header is set multiple times.
	 * @param headerName the header name
	 * @return all associated values
	 * @since 4.3
	 */
	public List<String> getValuesAsList(String headerName) {
		List<String> values = get(headerName);
		if (values != null) {
			List<String> result = new ArrayList<>();
			for (String value : values) {
				if (value != null) {
					Collections.addAll(result, StringUtils.tokenizeToStringArray(value, ","));
				}
			}
			return result;
		}
		return Collections.emptyList();
	}

	
Remove the well-known "Content-*" HTTP headers. 
Such headers should be cleared from the response if the intended
body can't be written due to errors.

Since:5.2.3
/**
	 * Remove the well-known {@code "Content-*"} HTTP headers.
	 * <p>Such headers should be cleared from the response if the intended
	 * body can't be written due to errors.
	 * @since 5.2.3
	 */
	public void clearContentHeaders() {
		this.headers.remove(HttpHeaders.CONTENT_DISPOSITION);
		this.headers.remove(HttpHeaders.CONTENT_ENCODING);
		this.headers.remove(HttpHeaders.CONTENT_LANGUAGE);
		this.headers.remove(HttpHeaders.CONTENT_LENGTH);
		this.headers.remove(HttpHeaders.CONTENT_LOCATION);
		this.headers.remove(HttpHeaders.CONTENT_RANGE);
		this.headers.remove(HttpHeaders.CONTENT_TYPE);
	}

	
Retrieve a combined result from the field values of the ETag header.

Params:
  • headerName – the header name
Throws:
Returns:the combined result
Since:4.3
/**
	 * Retrieve a combined result from the field values of the ETag header.
	 * @param headerName the header name
	 * @return the combined result
	 * @throws IllegalArgumentException if parsing fails
	 * @since 4.3
	 */
	protected List<String> getETagValuesAsList(String headerName) {
		List<String> values = get(headerName);
		if (values != null) {
			List<String> result = new ArrayList<>();
			for (String value : values) {
				if (value != null) {
					Matcher matcher = ETAG_HEADER_VALUE_PATTERN.matcher(value);
					while (matcher.find()) {
						if ("*".equals(matcher.group())) {
							result.add(matcher.group());
						}
						else {
							result.add(matcher.group(1));
						}
					}
					if (result.isEmpty()) {
						throw new IllegalArgumentException(
								"Could not parse header '" + headerName + "' with value '" + value + "'");
					}
				}
			}
			return result;
		}
		return Collections.emptyList();
	}

	
Retrieve a combined result from the field values of multi-valued headers.

Params:
  • headerName – the header name
Returns:the combined result
Since:4.3
/**
	 * Retrieve a combined result from the field values of multi-valued headers.
	 * @param headerName the header name
	 * @return the combined result
	 * @since 4.3
	 */
	@Nullable
	protected String getFieldValues(String headerName) {
		List<String> headerValues = get(headerName);
		return (headerValues != null ? toCommaDelimitedString(headerValues) : null);
	}

	
Turn the given list of header values into a comma-delimited result.

Params:
  • headerValues – the list of header values
Returns:a combined result with comma delimitation
/**
	 * Turn the given list of header values into a comma-delimited result.
	 * @param headerValues the list of header values
	 * @return a combined result with comma delimitation
	 */
	protected String toCommaDelimitedString(List<String> headerValues) {
		StringJoiner joiner = new StringJoiner(", ");
		for (String val : headerValues) {
			if (val != null) {
				joiner.add(val);
			}
		}
		return joiner.toString();
	}

	
Set the given header value, or remove the header if null. 
Params:
  • headerName – the header name
  • headerValue – the header value, or null for none
/**
	 * Set the given header value, or remove the header if {@code null}.
	 * @param headerName the header name
	 * @param headerValue the header value, or {@code null} for none
	 */
	private void setOrRemove(String headerName, @Nullable String headerValue) {
		if (headerValue != null) {
			set(headerName, headerValue);
		}
		else {
			remove(headerName);
		}
	}


	// MultiValueMap implementation

	
Return the first header value for the given header name, if any.

Params:
  • headerName – the header name
Returns:the first header value, or null if none
/**
	 * Return the first header value for the given header name, if any.
	 * @param headerName the header name
	 * @return the first header value, or {@code null} if none
	 */
	@Override
	@Nullable
	public String getFirst(String headerName) {
		return this.headers.getFirst(headerName);
	}

	
Add the given, single header value under the given name.

Params:
  • headerName – the header name
  • headerValue – the header value
Throws:
See Also:
/**
	 * Add the given, single header value under the given name.
	 * @param headerName the header name
	 * @param headerValue the header value
	 * @throws UnsupportedOperationException if adding headers is not supported
	 * @see #put(String, List)
	 * @see #set(String, String)
	 */
	@Override
	public void add(String headerName, @Nullable String headerValue) {
		this.headers.add(headerName, headerValue);
	}

	@Override
	public void addAll(String key, List<? extends String> values) {
		this.headers.addAll(key, values);
	}

	@Override
	public void addAll(MultiValueMap<String, String> values) {
		this.headers.addAll(values);
	}

	
Set the given, single header value under the given name.

Params:
  • headerName – the header name
  • headerValue – the header value
Throws:
See Also:
/**
	 * Set the given, single header value under the given name.
	 * @param headerName the header name
	 * @param headerValue the header value
	 * @throws UnsupportedOperationException if adding headers is not supported
	 * @see #put(String, List)
	 * @see #add(String, String)
	 */
	@Override
	public void set(String headerName, @Nullable String headerValue) {
		this.headers.set(headerName, headerValue);
	}

	@Override
	public void setAll(Map<String, String> values) {
		this.headers.setAll(values);
	}

	@Override
	public Map<String, String> toSingleValueMap() {
		return this.headers.toSingleValueMap();
	}


	// Map implementation

	@Override
	public int size() {
		return this.headers.size();
	}

	@Override
	public boolean isEmpty() {
		return this.headers.isEmpty();
	}

	@Override
	public boolean containsKey(Object key) {
		return this.headers.containsKey(key);
	}

	@Override
	public boolean containsValue(Object value) {
		return this.headers.containsValue(value);
	}

	@Override
	@Nullable
	public List<String> get(Object key) {
		return this.headers.get(key);
	}

	@Override
	public List<String> put(String key, List<String> value) {
		return this.headers.put(key, value);
	}

	@Override
	public List<String> remove(Object key) {
		return this.headers.remove(key);
	}

	@Override
	public void putAll(Map<? extends String, ? extends List<String>> map) {
		this.headers.putAll(map);
	}

	@Override
	public void clear() {
		this.headers.clear();
	}

	@Override
	public Set<String> keySet() {
		return this.headers.keySet();
	}

	@Override
	public Collection<List<String>> values() {
		return this.headers.values();
	}

	@Override
	public Set<Entry<String, List<String>>> entrySet() {
		return this.headers.entrySet();
	}


	@Override
	public boolean equals(@Nullable Object other) {
		if (this == other) {
			return true;
		}
		if (!(other instanceof HttpHeaders)) {
			return false;
		}
		return unwrap(this).equals(unwrap((HttpHeaders) other));
	}

	private static MultiValueMap<String, String> unwrap(HttpHeaders headers) {
		while (headers.headers instanceof HttpHeaders) {
			headers = (HttpHeaders) headers.headers;
		}
		return headers.headers;
	}

	@Override
	public int hashCode() {
		return this.headers.hashCode();
	}

	@Override
	public String toString() {
		return formatHeaders(this.headers);
	}


	
Apply a read-only HttpHeaders wrapper around the given headers, if necessary. 
Also caches the parsed representations of the "Accept" and "Content-Type" headers.

Params:
  • headers – the headers to expose
Returns:a read-only variant of the headers, or the original headers as-is (in case it happens to be a read-only HttpHeaders instance already)
Since:5.3
/**
	 * Apply a read-only {@code HttpHeaders} wrapper around the given headers, if necessary.
	 * <p>Also caches the parsed representations of the "Accept" and "Content-Type" headers.
	 * @param headers the headers to expose
	 * @return a read-only variant of the headers, or the original headers as-is
	 * (in case it happens to be a read-only {@code HttpHeaders} instance already)
	 * @since 5.3
	 */
	public static HttpHeaders readOnlyHttpHeaders(MultiValueMap<String, String> headers) {
		return (headers instanceof HttpHeaders ?
				readOnlyHttpHeaders((HttpHeaders) headers) : new ReadOnlyHttpHeaders(headers));
	}

	
Apply a read-only HttpHeaders wrapper around the given headers, if necessary. 
Also caches the parsed representations of the "Accept" and "Content-Type" headers.

Params:
  • headers – the headers to expose
Returns:a read-only variant of the headers, or the original headers as-is
/**
	 * Apply a read-only {@code HttpHeaders} wrapper around the given headers, if necessary.
	 * <p>Also caches the parsed representations of the "Accept" and "Content-Type" headers.
	 * @param headers the headers to expose
	 * @return a read-only variant of the headers, or the original headers as-is
	 */
	public static HttpHeaders readOnlyHttpHeaders(HttpHeaders headers) {
		Assert.notNull(headers, "HttpHeaders must not be null");
		return (headers instanceof ReadOnlyHttpHeaders ? headers : new ReadOnlyHttpHeaders(headers.headers));
	}

	
Remove any read-only wrapper that may have been previously applied around the given headers via readOnlyHttpHeaders(HttpHeaders). 
Params:
  • headers – the headers to expose
Returns:a writable variant of the headers, or the original headers as-is
Since:5.1.1
/**
	 * Remove any read-only wrapper that may have been previously applied around
	 * the given headers via {@link #readOnlyHttpHeaders(HttpHeaders)}.
	 * @param headers the headers to expose
	 * @return a writable variant of the headers, or the original headers as-is
	 * @since 5.1.1
	 */
	public static HttpHeaders writableHttpHeaders(HttpHeaders headers) {
		Assert.notNull(headers, "HttpHeaders must not be null");
		if (headers == EMPTY) {
			return new HttpHeaders();
		}
		return (headers instanceof ReadOnlyHttpHeaders ? new HttpHeaders(headers.headers) : headers);
	}

	
Helps to format HTTP header values, as HTTP header values themselves can contain comma-separated values, can become confusing with regular Map formatting that also uses commas between entries. 
Params:
  • headers – the headers to format
Returns:the headers to a String
Since:5.1.4
/**
	 * Helps to format HTTP header values, as HTTP header values themselves can
	 * contain comma-separated values, can become confusing with regular
	 * {@link Map} formatting that also uses commas between entries.
	 * @param headers the headers to format
	 * @return the headers to a String
	 * @since 5.1.4
	 */
	public static String formatHeaders(MultiValueMap<String, String> headers) {
		return headers.entrySet().stream()
				.map(entry -> {
					List<String> values = entry.getValue();
					return entry.getKey() + ":" + (values.size() == 1 ?
							"\"" + values.get(0) + "\"" :
							values.stream().map(s -> "\"" + s + "\"").collect(Collectors.joining(", ")));
				})
				.collect(Collectors.joining(", ", "[", "]"));
	}

	
Encode the given username and password into Basic Authentication credentials.

The encoded credentials returned by this method can be supplied to setBasicAuth(String) to set the Basic Authentication header. 
Params:
  • username – the username
  • password – the password
  • charset – the charset to use to convert the credentials into an octet sequence. Defaults to ISO-8859-1.
Throws:
See Also:
Since:5.2
/**
	 * Encode the given username and password into Basic Authentication credentials.
	 * <p>The encoded credentials returned by this method can be supplied to
	 * {@link #setBasicAuth(String)} to set the Basic Authentication header.
	 * @param username the username
	 * @param password the password
	 * @param charset the charset to use to convert the credentials into an octet
	 * sequence. Defaults to {@linkplain StandardCharsets#ISO_8859_1 ISO-8859-1}.
	 * @throws IllegalArgumentException if {@code username} or {@code password}
	 * contains characters that cannot be encoded to the given charset
	 * @since 5.2
	 * @see #setBasicAuth(String)
	 * @see #setBasicAuth(String, String)
	 * @see #setBasicAuth(String, String, Charset)
	 * @see <a href="https://tools.ietf.org/html/rfc7617">RFC 7617</a>
	 */
	public static String encodeBasicAuth(String username, String password, @Nullable Charset charset) {
		Assert.notNull(username, "Username must not be null");
		Assert.doesNotContain(username, ":", "Username must not contain a colon");
		Assert.notNull(password, "Password must not be null");
		if (charset == null) {
			charset = StandardCharsets.ISO_8859_1;
		}

		CharsetEncoder encoder = charset.newEncoder();
		if (!encoder.canEncode(username) || !encoder.canEncode(password)) {
			throw new IllegalArgumentException(
					"Username or password contains characters that cannot be encoded to " + charset.displayName());
		}

		String credentialsString = username + ":" + password;
		byte[] encodedBytes = Base64.getEncoder().encode(credentialsString.getBytes(charset));
		return new String(encodedBytes, charset);
	}

	// Package-private: used in ResponseCookie
	static String formatDate(long date) {
		Instant instant = Instant.ofEpochMilli(date);
		ZonedDateTime time = ZonedDateTime.ofInstant(instant, GMT);
		return DATE_FORMATTER.format(time);
	}

}