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 org.apache.juneau.http.annotation.*; 016 017/** 018 * Represents a parsed <l>Expect</l> HTTP request header. 019 * 020 * <p> 021 * Indicates that particular server behaviors are required by the client. 022 * 023 * <h5 class='figure'>Example</h5> 024 * <p class='bcode w800'> 025 * Expect: 100-continue 026 * </p> 027 * 028 * <h5 class='topic'>RFC2616 Specification</h5> 029 * 030 * The Expect request-header field is used to indicate that particular server behaviors are required by the client. 031 * <p class='bcode w800'> 032 * Expect = "Expect" ":" 1#expectation 033 * expectation = "100-continue" | expectation-extension 034 * expectation-extension = token [ "=" ( token | quoted-string ) 035 * *expect-params ] 036 * expect-params = ";" token [ "=" ( token | quoted-string ) ] 037 * </p> 038 * 039 * <p> 040 * A server that does not understand or is unable to comply with any of the expectation values in the Expect field of a 041 * request MUST respond with appropriate error status. 042 * The server MUST respond with a 417 (Expectation Failed) status if any of the expectations cannot be met or, if there 043 * are other problems with the request, some other 4xx status. 044 * 045 * <p> 046 * This header field is defined with extensible syntax to allow for future extensions. 047 * If a server receives a request containing an Expect field that includes an expectation-extension that it does not 048 * support, it MUST respond with a 417 (Expectation Failed) status. 049 * 050 * <p> 051 * Comparison of expectation values is case-insensitive for unquoted tokens (including the 100-continue token), and is 052 * case-sensitive for quoted-string expectation-extensions. 053 * 054 * <p> 055 * The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST return a 417 (Expectation Failed) status if it 056 * receives a request with an expectation that it cannot meet. 057 * However, the Expect request-header itself is end-to-end; it MUST be forwarded if the request is forwarded. 058 * 059 * <p> 060 * Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header. 061 * 062 * <p> 063 * See section 8.2.3 for the use of the 100 (continue) status. 064 * 065 * <ul class='seealso'> 066 * <li class='extlink'>{@doc RFC2616} 067 * </ul> 068 */ 069@Header("Expect") 070public final class Expect extends HeaderString { 071 072 /** 073 * Returns a parsed <c>Expect</c> header. 074 * 075 * @param value The <c>Expect</c> header string. 076 * @return The parsed <c>Expect</c> header, or <jk>null</jk> if the string was null. 077 */ 078 public static Expect forString(String value) { 079 if (value == null) 080 return null; 081 return new Expect(value); 082 } 083 084 private Expect(String value) { 085 super(value); 086 } 087}