| // *************************************************************************************************************************** |
| // * 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>Vary</l> HTTP response header. |
| * |
| * <p> |
| * Tells downstream proxies how to match future request headers to decide whether the cached response can be used rather |
| * than requesting a fresh one from the origin server. |
| * |
| * <h5 class='figure'>Example</h5> |
| * <p class='bcode w800'> |
| * Vary: * |
| * Vary: Accept-Language |
| * </p> |
| * |
| * <h5 class='topic'>RFC2616 Specification</h5> |
| * |
| * The Vary field value indicates the set of request-header fields that fully determines, while the response is fresh, |
| * whether a cache is permitted to use the response to reply to a subsequent request without revalidation. |
| * For uncacheable or stale responses, the Vary field value advises the user agent about the criteria that were used to |
| * select the representation. |
| * A Vary field value of "*" implies that a cache cannot determine from the request headers of a subsequent request |
| * whether this response is the appropriate representation. |
| * See section 13.6 for use of the Vary header field by caches. |
| * <p class='bcode w800'> |
| * Vary = "Vary" ":" ( "*" | 1#field-name ) |
| * </p> |
| * |
| * <p> |
| * An HTTP/1.1 server SHOULD include a Vary header field with any cacheable response that is subject to server-driven |
| * negotiation. |
| * Doing so allows a cache to properly interpret future requests on that resource and informs the user agent about the |
| * presence of negotiation on that resource. |
| * A server MAY include a Vary header field with a non-cacheable response that is subject to server-driven negotiation, |
| * since this might provide the user agent with useful information about the dimensions over which the response varies |
| * at the time of the response. |
| * |
| * <p> |
| * A Vary field value consisting of a list of field-names signals that the representation selected for the response is |
| * based on a selection algorithm which considers ONLY the listed request-header field values in selecting the most |
| * appropriate representation. |
| * A cache MAY assume that the same selection will be made for future requests with the same values for the listed |
| * field names, for the duration of time for which the response is fresh. |
| * |
| * <p> |
| * The field-names given are not limited to the set of standard request-header fields defined by this specification. |
| * Field names are case-insensitive. |
| * |
| * <p> |
| * A Vary field value of "*" signals that unspecified parameters not limited to the request-headers (e.g., the network |
| * address of the client), play a role in the selection of the response representation. |
| * The "*" value MUST NOT be generated by a proxy server; it may only be generated by an origin server. |
| * |
| * <ul class='seealso'> |
| * <li class='extlink'>{@doc RFC2616} |
| * </ul> |
| */ |
| @Header("Vary") |
| public final class Vary extends HeaderString { |
| |
| /** |
| * Returns a parsed <c>Vary</c> header. |
| * |
| * @param value The <c>Vary</c> header string. |
| * @return The parsed <c>Vary</c> header, or <jk>null</jk> if the string was null. |
| */ |
| public static Vary forString(String value) { |
| if (value == null) |
| return null; |
| return new Vary(value); |
| } |
| |
| private Vary(String value) { |
| super(value); |
| } |
| } |