| // *************************************************************************************************************************** |
| // * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file * |
| // * distributed with this work for additional information regarding copyright ownership. The ASF licenses this file * |
| // * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance * |
| // * with the License. You may obtain a copy of the License at * |
| // * * |
| // * http://www.apache.org/licenses/LICENSE-2.0 * |
| // * * |
| // * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an * |
| // * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the * |
| // * specific language governing permissions and limitations under the License. * |
| // *************************************************************************************************************************** |
| package org.apache.juneau.http; |
| |
| import org.apache.juneau.http.annotation.*; |
| |
| /** |
| * Represents a parsed <l>If-Match</l> HTTP request header. |
| * |
| * <p> |
| * Only perform the action if the client supplied entity matches the same entity on the server. |
| * This is mainly for methods like PUT to only update a resource if it has not been modified since the user last |
| * updated it. |
| * |
| * <h5 class='figure'>Example</h5> |
| * <p class='bcode w800'> |
| * If-Match: "737060cd8c284d8af7ad3082f209582d" |
| * </p> |
| * |
| * <h5 class='topic'>RFC2616 Specification</h5> |
| * |
| * The If-Match request-header field is used with a method to make it conditional. |
| * A client that has one or more entities previously obtained from the resource can verify that one of those entities |
| * is current by including a list of their associated entity tags in the If-Match header field. |
| * Entity tags are defined in section 3.11. |
| * The purpose of this feature is to allow efficient updates of cached information with a minimum amount of transaction |
| * overhead. |
| * It is also used, on updating requests, to prevent inadvertent modification of the wrong version of a resource. |
| * As a special case, the value "*" matches any current entity of the resource. |
| * |
| * <p class='bcode w800'> |
| * If-Match = "If-Match" ":" ( "*" | 1#entity-tag ) |
| * </p> |
| * |
| * <p> |
| * If any of the entity tags match the entity tag of the entity that would have been returned in the response to a |
| * similar GET request (without the If-Match header) on that resource, or if "*" is given and any current entity exists |
| * for that resource, then the server MAY perform the requested method as if the If-Match header field did not exist. |
| * |
| * <p> |
| * A server MUST use the strong comparison function (see section 13.3.3) to compare the entity tags in If-Match. |
| * |
| * <p> |
| * If none of the entity tags match, or if "*" is given and no current entity exists, the server MUST NOT perform the |
| * requested method, and MUST return a 412 (Precondition Failed) response. |
| * This behavior is most useful when the client wants to prevent an updating method, such as PUT, from modifying a |
| * resource that has changed since the client last retrieved it. |
| * |
| * <p> |
| * If the request would, without the If-Match header field, result in anything other than a 2xx or 412 status, then the |
| * If-Match header MUST be ignored. |
| * |
| * <p> |
| * The meaning of "If-Match: *" is that the method SHOULD be performed if the representation selected by the origin |
| * server (or by a cache, possibly using the Vary mechanism, see section 14.44) exists, and MUST NOT be performed if the |
| * representation does not exist. |
| * |
| * <p> |
| * A request intended to update a resource (e.g., a PUT) MAY include an If-Match header field to signal that the request |
| * method MUST NOT be applied if the entity corresponding to the If-Match value (a single entity tag) is no longer a |
| * representation of that resource. |
| * This allows the user to indicate that they do not wish the request to be successful if the resource has been changed |
| * without their knowledge. |
| * |
| * <p> |
| * Examples: |
| * <p class='bcode w800'> |
| * If-Match: "xyzzy" |
| * If-Match: "xyzzy", "r2d2xxxx", "c3piozzzz" |
| * If-Match: * |
| * </p> |
| * |
| * <p> |
| * The result of a request having both an If-Match header field and either an If-None-Match or an If-Modified-Since |
| * header fields is undefined by this specification. |
| * |
| * <ul class='seealso'> |
| * <li class='extlink'>{@doc RFC2616} |
| * </ul> |
| */ |
| @Header("If-Match") |
| public final class IfMatch extends HeaderEntityValidatorArray { |
| |
| /** |
| * Returns a parsed <c>If-Match</c> header. |
| * |
| * @param value The <c>If-Match</c> header string. |
| * @return The parsed <c>If-Match</c> header, or <jk>null</jk> if the string was null. |
| */ |
| public static IfMatch forString(String value) { |
| if (value == null) |
| return null; |
| return new IfMatch(value); |
| } |
| |
| private IfMatch(String value) { |
| super(value); |
| } |
| } |