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; 014 015import static org.apache.juneau.http.Constants.*; 016 017import org.apache.juneau.http.annotation.*; 018import org.apache.juneau.internal.*; 019 020/** 021 * Represents a parsed <l>Accept-Encoding</l> HTTP request header. 022 * 023 * <p> 024 * List of acceptable encodings. 025 * 026 * <h5 class='figure'>Example</h5> 027 * <p class='bcode w800'> 028 * Accept-Encoding: gzip, deflate 029 * </p> 030 * 031 * <h5 class='topic'>RFC2616 Specification</h5> 032 * 033 * The Accept-Encoding request-header field is similar to Accept, but restricts the content-codings (section 3.5) that 034 * are acceptable in the response. 035 * 036 * <p class='bcode w800'> 037 * Accept-Encoding = "Accept-Encoding" ":" 038 * 1#( codings [ ";" "q" "=" qvalue ] ) 039 * codings = ( content-coding | "*" ) 040 * </p> 041 * 042 * <p> 043 * Examples of its use are: 044 * <p class='bcode w800'> 045 * Accept-Encoding: compress, gzip 046 * Accept-Encoding: 047 * Accept-Encoding: * 048 * Accept-Encoding: compress;q=0.5, gzip;q=1.0 049 * Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0 050 * </p> 051 * 052 * <p> 053 * A server tests whether a content-coding is acceptable, according to an Accept-Encoding field, using these rules: 054 * <ol> 055 * <li>If the content-coding is one of the content-codings listed in the Accept-Encoding field, then it is 056 * acceptable, unless it is accompanied by a qvalue of 0. 057 * (As defined in section 3.9, a qvalue of 0 means "not acceptable.") 058 * <li>The special "*" symbol in an Accept-Encoding field matches any available content-coding not explicitly listed 059 * in the header field. 060 * <li>If multiple content-codings are acceptable, then the acceptable content-coding with the highest non-zero 061 * qvalue is preferred. 062 * <li>The "identity" content-coding is always acceptable, unless specifically refused because the Accept-Encoding 063 * field includes "identity;q=0", or because the field includes "*;q=0" and does not explicitly include the 064 * "identity" content-coding. 065 * If the Accept-Encoding field-value is empty, then only the "identity" encoding is acceptable. 066 * </ol> 067 * 068 * <p> 069 * If an Accept-Encoding field is present in a request, and if the server cannot send a response which is acceptable 070 * according to the Accept-Encoding header, then the server SHOULD send an error response with the 406 (Not Acceptable) 071 * status code. 072 * 073 * <p> 074 * If no Accept-Encoding field is present in a request, the server MAY assume that the client will accept any content 075 * coding. 076 * In this case, if "identity" is one of the available content-codings, then the server SHOULD use the "identity" 077 * content-coding, unless it has additional information that a different content-coding is meaningful to the client. 078 * 079 * <p> 080 * Note: If the request does not include an Accept-Encoding field, and if the "identity" content-coding is unavailable, 081 * then content-codings commonly understood by HTTP/1.0 clients (i.e.,"gzip" and "compress") are preferred; some older 082 * clients improperly display messages sent with other content-codings. 083 * The server might also make this decision based on information about the particular user-agent or client. 084 * 085 * <p> 086 * Note: Most HTTP/1.0 applications do not recognize or obey qvalues associated with content-codings. 087 * This means that qvalues will not work and are not permitted with x-gzip or x-compress. 088 * 089 * <h5 class='section'>See Also:</h5> 090 * <ul class='doctree'> 091 * <li class='extlink'>{@doc RFC2616} 092 * </ul> 093 */ 094@Header("Accept-Encoding") 095public final class AcceptEncoding extends HeaderRangeArray { 096 097 private static final Cache<String,AcceptEncoding> cache = new Cache<>(NOCACHE, CACHE_MAX_SIZE); 098 099 /** 100 * Returns a parsed <code>Accept-Encoding</code> header. 101 * 102 * @param value The <code>Accept-Encoding</code> header string. 103 * @return The parsed <code>Accept-Encoding</code> header, or <jk>null</jk> if the string was null. 104 */ 105 public static AcceptEncoding forString(String value) { 106 if (value == null) 107 return null; 108 AcceptEncoding a = cache.get(value); 109 if (a == null) 110 a = cache.put(value, new AcceptEncoding(value)); 111 return a; 112 } 113 114 private AcceptEncoding(String value) { 115 super(value); 116 } 117}