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.*; 018import org.apache.juneau.http.annotation.*; 019 020/** 021 * Represents a parsed <l>If-None-Match</l> HTTP request header. 022 * 023 * <p> 024 * Allows a 304 Not Modified to be returned if content is unchanged. 025 * 026 * <h5 class='figure'>Example</h5> 027 * <p class='bcode w800'> 028 * If-None-Match: "737060cd8c284d8af7ad3082f209582d" 029 * </p> 030 * 031 * <h5 class='topic'>RFC2616 Specification</h5> 032 * 033 * The If-None-Match request-header field is used with a method to make it conditional. 034 * A client that has one or more entities previously obtained from the resource can verify that none of those entities 035 * is current by including a list of their associated entity tags in the If-None-Match header field. 036 * The purpose of this feature is to allow efficient updates of cached information with a minimum amount of transaction 037 * overhead. 038 * It is also used to prevent a method (e.g. PUT) from inadvertently modifying an existing resource when the client 039 * believes that the resource does not exist. 040 * 041 * <p> 042 * As a special case, the value "*" matches any current entity of the resource. 043 * 044 * <p class='bcode w800'> 045 * If-None-Match = "If-None-Match" ":" ( "*" | 1#entity-tag ) 046 * </p> 047 * 048 * <p> 049 * If any of the entity tags match the entity tag of the entity that would have been returned in the response to a 050 * similar GET request (without the If-None-Match header) on that resource, or if "*" is given 051 * and any current entity exists for that resource, then the server MUST NOT perform the requested method, unless 052 * required to do so because the resource's modification date fails to match that supplied in an If-Modified-Since 053 * header field in the request. 054 * Instead, if the request method was GET or HEAD, the server SHOULD respond with a 304 (Not Modified) response, 055 * including the cache- related header fields (particularly ETag) of one of the entities that matched. 056 * For all other request methods, the server MUST respond with a status of 412 (Precondition Failed). 057 * 058 * <p> 059 * See section 13.3.3 for rules on how to determine if two entities tags match. 060 * The weak comparison function can only be used with GET or HEAD requests. 061 * 062 * <p> 063 * If none of the entity tags match, then the server MAY perform the requested method as if the If-None-Match header 064 * field did not exist, but MUST also ignore any If-Modified-Since header field(s) in the request. 065 * That is, if no entity tags match, then the server MUST NOT return a 304 (Not Modified) response. 066 * 067 * <p> 068 * If the request would, without the If-None-Match header field, result in anything other than a 2xx or 304 status, 069 * then the If-None-Match header MUST be ignored. 070 * (See section 13.3.4 for a discussion of server behavior when both If-Modified-Since and If-None-Match appear in the 071 * same request.) 072 * 073 * <p> 074 * The meaning of "If-None-Match: *" is that the method MUST NOT be performed if the representation selected by the 075 * origin server (or by a cache, possibly using the Vary mechanism, see section 14.44) exists, and SHOULD be performed 076 * if the representation does not exist. 077 * This feature is intended to be useful in preventing races between PUT operations. 078 * 079 * <p> 080 * Examples: 081 * <p class='bcode w800'> 082 * If-None-Match: "xyzzy" 083 * If-None-Match: W/"xyzzy" 084 * If-None-Match: "xyzzy", "r2d2xxxx", "c3piozzzz" 085 * If-None-Match: W/"xyzzy", W/"r2d2xxxx", W/"c3piozzzz" 086 * If-None-Match: * 087 * </p> 088 * 089 * <p> 090 * The result of a request having both an If-None-Match header field and either an If-Match or an If-Unmodified-Since 091 * header fields is undefined by this specification. 092 * 093 * <ul class='seealso'> 094 * <li class='extlink'>{@doc ExtRFC2616} 095 * </ul> 096 */ 097@Header("If-None-Match") 098public class IfNoneMatch extends BasicEntityTagArrayHeader { 099 100 private static final long serialVersionUID = 1L; 101 102 /** 103 * Convenience creator. 104 * 105 * @param value 106 * The header value. 107 * <br>Can be any of the following: 108 * <ul> 109 * <li><c>String</c> - A comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>). 110 * <li>A collection or array of {@link EntityTag} objects. 111 * <li>A collection or array of anything else - Converted to Strings. 112 * <li>Anything else - Converted to <c>String</c>. 113 * </ul> 114 * @return A new {@link IfNoneMatch} object. 115 */ 116 public static IfNoneMatch of(Object value) { 117 if (value == null) 118 return null; 119 return new IfNoneMatch(value); 120 } 121 122 /** 123 * Convenience creator using supplier. 124 * 125 * <p> 126 * Header value is re-evaluated on each call to {@link #getValue()}. 127 * 128 * @param value 129 * The header value supplier. 130 * <br>Can be any of the following: 131 * <ul> 132 * <li><c>String</c> - A comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>). 133 * <li>A collection or array of {@link EntityTag} objects. 134 * <li>A collection or array of anything else - Converted to Strings. 135 * <li>Anything else - Converted to <c>String</c>. 136 * </ul> 137 * @return A new {@link IfNoneMatch} object. 138 */ 139 public static IfNoneMatch of(Supplier<?> value) { 140 if (value == null) 141 return null; 142 return new IfNoneMatch(value); 143 } 144 145 /** 146 * Constructor. 147 * 148 * @param value 149 * The header value. 150 * <br>Can be any of the following: 151 * <ul> 152 * <li><c>String</c> - A comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>). 153 * <li>A collection or array of {@link EntityTag} objects. 154 * <li>A collection or array of anything else - Converted to Strings. 155 * <li>Anything else - Converted to <c>String</c>. 156 * <li>A {@link Supplier} of anything on this list. 157 * </ul> 158 */ 159 public IfNoneMatch(Object value) { 160 super("If-None-Match", value); 161 } 162 163 /** 164 * Constructor 165 * 166 * @param value 167 * The header value. 168 */ 169 public IfNoneMatch(String value) { 170 this((Object)value); 171 } 172}