001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
003// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
009// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an  *
010// * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the        *
011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.http.header;
014
015import java.util.function.*;
016
017import org.apache.juneau.http.annotation.*;
018
019/**
020 * Represents a parsed <l>Cache-Control</l> HTTP request header.
021 *
022 * <p>
023 * Used to specify directives that must be obeyed by all caching mechanisms along the request-response chain.
024 *
025 * <h5 class='figure'>Example</h5>
026 * <p class='bcode w800'>
027 *    Cache-Control: no-cache
028 * </p>
029 *
030 * <h5 class='topic'>RFC2616 Specification</h5>
031 *
032 * The Cache-Control general-header field is used to specify directives that MUST be obeyed by all caching mechanisms
033 * along the request/response chain.
034 * The directives specify behavior intended to prevent caches from adversely interfering with the request or response.
035 * These directives typically override the default caching algorithms.
036 * Cache directives are unidirectional in that the presence of a directive in a request does not imply that the same
037 * directive is to be given in the response.
038 *
039 * <p>
040 * Note that HTTP/1.0 caches might not implement Cache-Control and might only implement Pragma: no-cache (see section
041 * 14.32).
042 *
043 * <p>
044 * Cache directives MUST be passed through by a proxy or gateway application, regardless of their significance to that
045 * application, since the directives might be applicable to all recipients along the request/response chain.
046 * It is not possible to specify a cache- directive for a specific cache.
047 *
048 * <p class='bcode w800'>
049 *    Cache-Control   = "Cache-Control" ":" 1#cache-directive
050 *    cache-directive = cache-request-directive
051 *         | cache-response-directive
052 *    cache-request-directive =
053 *           "no-cache"                          ; Section 14.9.1
054 *         | "no-store"                          ; Section 14.9.2
055 *         | "max-age" "=" delta-seconds         ; Section 14.9.3, 14.9.4
056 *         | "max-stale" [ "=" delta-seconds ]   ; Section 14.9.3
057 *         | "min-fresh" "=" delta-seconds       ; Section 14.9.3
058 *         | "no-transform"                      ; Section 14.9.5
059 *         | "only-if-cached"                    ; Section 14.9.4
060 *         | cache-extension                     ; Section 14.9.6
061 *    cache-response-directive =
062 *           "public"                               ; Section 14.9.1
063 *         | "private" [ "=" &lt;"&gt; 1#field-name &lt;"&gt; ] ; Section 14.9.1
064 *         | "no-cache" [ "=" &lt;"&gt; 1#field-name &lt;"&gt; ]; Section 14.9.1
065 *         | "no-store"                             ; Section 14.9.2
066 *         | "no-transform"                         ; Section 14.9.5
067 *         | "must-revalidate"                      ; Section 14.9.4
068 *         | "proxy-revalidate"                     ; Section 14.9.4
069 *         | "max-age" "=" delta-seconds            ; Section 14.9.3
070 *         | "s-maxage" "=" delta-seconds           ; Section 14.9.3
071 *         | cache-extension                        ; Section 14.9.6
072 *    cache-extension = token [ "=" ( token | quoted-string ) ]
073 * </p>
074 *
075 * <p>
076 * When a directive appears without any 1#field-name parameter, the directive applies to the entire request or response.
077 * When such a directive appears with a 1#field-name parameter, it applies only to the named field or fields, and not
078 * to the rest of the request or response. This mechanism supports extensibility; implementations of future versions
079 * of the HTTP protocol might apply these directives to header fields not defined in HTTP/1.1.
080 *
081 * <p>
082 * The cache-control directives can be broken down into these general categories:
083 * <ul>
084 *    <li>Restrictions on what are cacheable; these may only be imposed by the origin server.
085 *    <li>Restrictions on what may be stored by a cache; these may be imposed by either the origin server or the user
086 *       agent.
087 *    <li>Modifications of the basic expiration mechanism; these may be imposed by either the origin server or the
088 *       user agent.
089 *    <li>Controls over cache revalidation and reload; these may only be imposed by a user agent.
090 *    <li>Control over transformation of entities.
091 *    <li>Extensions to the caching system.
092 * </ul>
093 *
094 * <ul class='seealso'>
095 *    <li class='extlink'>{@doc ExtRFC2616}
096 * </ul>
097 */
098@Header("Cache-Control")
099public class CacheControl extends BasicStringHeader {
100
101   private static final long serialVersionUID = 1L;
102
103   /**
104    * Convenience creator.
105    *
106    * @param value
107    *    The header value.
108    *    <br>Can be any of the following:
109    *    <ul>
110    *       <li>{@link String}
111    *       <li>Anything else - Converted to <c>String</c> then parsed.
112    *    </ul>
113    * @return A new {@link CacheControl} object.
114    */
115   public static CacheControl of(Object value) {
116      if (value == null)
117         return null;
118      return new CacheControl(value);
119   }
120
121   /**
122    * Convenience creator using supplier.
123    *
124    * <p>
125    * Header value is re-evaluated on each call to {@link #getValue()}.
126    *
127    * @param value
128    *    The header value supplier.
129    *    <br>Can be any of the following:
130    *    <ul>
131    *       <li>{@link String}
132    *       <li>Anything else - Converted to <c>String</c> then parsed.
133    *    </ul>
134    * @return A new {@link CacheControl} object.
135    */
136   public static CacheControl of(Supplier<?> value) {
137      if (value == null)
138         return null;
139      return new CacheControl(value);
140   }
141
142   /**
143    * Constructor.
144    *
145    * @param value
146    *    The header value.
147    *    <br>Can be any of the following:
148    *    <ul>
149    *       <li>{@link String}
150    *       <li>Anything else - Converted to <c>String</c> then parsed.
151    *       <li>A {@link Supplier} of anything on this list.
152    *    </ul>
153    */
154   public CacheControl(Object value) {
155      super("Cache-Control", value);
156   }
157
158   /**
159    * Constructor
160    *
161    * @param value
162    *    The header value.
163    */
164   public CacheControl(String value) {
165      this((Object)value);
166   }
167}