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>If-Unmodified-Since</l> HTTP request header. 019 * 020 * <p> 021 * Only send the response if the entity has not been modified since a specific time. 022 * 023 * <h5 class='figure'>Example</h5> 024 * <p class='bcode w800'> 025 * If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT 026 * </p> 027 * 028 * <h5 class='topic'>RFC2616 Specification</h5> 029 * 030 * The If-Unmodified-Since request-header field is used with a method to make it conditional. 031 * If the requested resource has not been modified since the time specified in this field, the server SHOULD perform the 032 * requested operation as if the If-Unmodified-Since header were not present. 033 * 034 * <p> 035 * If the requested variant has been modified since the specified time, the server MUST NOT perform the requested 036 * operation, and MUST return a 412 (Precondition Failed). 037 * 038 * <p class='bcode w800'> 039 * If-Unmodified-Since = "If-Unmodified-Since" ":" HTTP-date 040 * </p> 041 * 042 * <p> 043 * An example of the field is: 044 * <p class='bcode w800'> 045 * If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT 046 * </p> 047 * 048 * <p> 049 * If the request normally (i.e., without the If-Unmodified-Since header) would result in anything other than a 2xx or 050 * 412 status, the If-Unmodified-Since header SHOULD be ignored. 051 * 052 * <p> 053 * If the specified date is invalid, the header is ignored. 054 * 055 * <p> 056 * The result of a request having both an If-Unmodified-Since header field and either an If-None-Match or an 057 * If-Modified-Since header fields is undefined by this specification. 058 * 059 * <h5 class='section'>See Also:</h5> 060 * <ul class='doctree'> 061 * <li class='extlink'>{@doc RFC2616} 062 * </ul> 063 */ 064@Header("If-Unmodified-Since") 065public final class IfUnmodifiedSince extends HeaderDate { 066 067 /** 068 * Returns a parsed <code>If-Unmodified-Since</code> header. 069 * 070 * @param value The <code>If-Unmodified-Since</code> header string. 071 * @return The parsed <code>If-Unmodified-Since</code> header, or <jk>null</jk> if the string was null. 072 */ 073 public static IfUnmodifiedSince forString(String value) { 074 if (value == null) 075 return null; 076 return new IfUnmodifiedSince(value); 077 } 078 079 private IfUnmodifiedSince(String value) { 080 super(value); 081 } 082}