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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-Match</l> HTTP request header. 022 * 023 * <p> 024 * Only perform the action if the client supplied entity matches the same entity on the server. 025 * This is mainly for methods like PUT to only update a resource if it has not been modified since the user last 026 * updated it. 027 * 028 * <h5 class='figure'>Example</h5> 029 * <p class='bcode w800'> 030 * If-Match: "737060cd8c284d8af7ad3082f209582d" 031 * </p> 032 * 033 * <h5 class='topic'>RFC2616 Specification</h5> 034 * 035 * The If-Match request-header field is used with a method to make it conditional. 036 * A client that has one or more entities previously obtained from the resource can verify that one of those entities 037 * is current by including a list of their associated entity tags in the If-Match header field. 038 * Entity tags are defined in section 3.11. 039 * The purpose of this feature is to allow efficient updates of cached information with a minimum amount of transaction 040 * overhead. 041 * It is also used, on updating requests, to prevent inadvertent modification of the wrong version of a resource. 042 * As a special case, the value "*" matches any current entity of the resource. 043 * 044 * <p class='bcode w800'> 045 * If-Match = "If-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-Match header) on that resource, or if "*" is given and any current entity exists 051 * for that resource, then the server MAY perform the requested method as if the If-Match header field did not exist. 052 * 053 * <p> 054 * A server MUST use the strong comparison function (see section 13.3.3) to compare the entity tags in If-Match. 055 * 056 * <p> 057 * If none of the entity tags match, or if "*" is given and no current entity exists, the server MUST NOT perform the 058 * requested method, and MUST return a 412 (Precondition Failed) response. 059 * This behavior is most useful when the client wants to prevent an updating method, such as PUT, from modifying a 060 * resource that has changed since the client last retrieved it. 061 * 062 * <p> 063 * If the request would, without the If-Match header field, result in anything other than a 2xx or 412 status, then the 064 * If-Match header MUST be ignored. 065 * 066 * <p> 067 * The meaning of "If-Match: *" is that the method SHOULD be performed if the representation selected by the origin 068 * server (or by a cache, possibly using the Vary mechanism, see section 14.44) exists, and MUST NOT be performed if the 069 * representation does not exist. 070 * 071 * <p> 072 * A request intended to update a resource (e.g., a PUT) MAY include an If-Match header field to signal that the request 073 * method MUST NOT be applied if the entity corresponding to the If-Match value (a single entity tag) is no longer a 074 * representation of that resource. 075 * This allows the user to indicate that they do not wish the request to be successful if the resource has been changed 076 * without their knowledge. 077 * 078 * <p> 079 * Examples: 080 * <p class='bcode w800'> 081 * If-Match: "xyzzy" 082 * If-Match: "xyzzy", "r2d2xxxx", "c3piozzzz" 083 * If-Match: * 084 * </p> 085 * 086 * <p> 087 * The result of a request having both an If-Match header field and either an If-None-Match or an If-Modified-Since 088 * header fields is undefined by this specification. 089 * 090 * <ul class='seealso'> 091 * <li class='extlink'>{@doc ExtRFC2616} 092 * </ul> 093 */ 094@Header("If-Match") 095public class IfMatch extends BasicEntityTagArrayHeader { 096 097 private static final long serialVersionUID = 1L; 098 099 /** 100 * Convenience creator. 101 * 102 * @param value 103 * The header value. 104 * <br>Can be any of the following: 105 * <ul> 106 * <li><c>String</c> - A comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>). 107 * <li>A collection or array of {@link EntityTag} objects. 108 * <li>A collection or array of anything else - Converted to Strings. 109 * <li>Anything else - Converted to <c>String</c>. 110 * </ul> 111 * @return A new {@link IfMatch} object. 112 */ 113 public static IfMatch of(Object value) { 114 if (value == null) 115 return null; 116 return new IfMatch(value); 117 } 118 119 /** 120 * Convenience creator using supplier. 121 * 122 * <p> 123 * Header value is re-evaluated on each call to {@link #getValue()}. 124 * 125 * @param value 126 * The header value supplier. 127 * <br>Can be any of the following: 128 * <ul> 129 * <li><c>String</c> - A comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>). 130 * <li>A collection or array of {@link EntityTag} objects. 131 * <li>A collection or array of anything else - Converted to Strings. 132 * <li>Anything else - Converted to <c>String</c>. 133 * </ul> 134 * @return A new {@link IfMatch} object. 135 */ 136 public static IfMatch of(Supplier<?> value) { 137 if (value == null) 138 return null; 139 return new IfMatch(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><c>String</c> - A comma-delimited list of entity validator values (e.g. <js>"\"xyzzy\", \"r2d2xxxx\", \"c3piozzzz\""</js>). 150 * <li>A collection or array of {@link EntityTag} objects. 151 * <li>A collection or array of anything else - Converted to Strings. 152 * <li>Anything else - Converted to <c>String</c>. 153 * <li>A {@link Supplier} of anything on this list. 154 * </ul> 155 */ 156 public IfMatch(Object value) { 157 super("If-Match", value); 158 } 159 160 /** 161 * Constructor 162 * 163 * @param value 164 * The header value. 165 */ 166 public IfMatch(String value) { 167 this((Object)value); 168 } 169}