org.apache.juneau.http.IfUnmodifiedSince Maven / Gradle / Ivy
// ***************************************************************************************************************************
// * 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;
/**
* Represents a parsed If-Unmodified-Since HTTP request header.
*
*
* Only send the response if the entity has not been modified since a specific time.
*
*
Example
*
* If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT
*
*
* RFC2616 Specification
*
* The If-Unmodified-Since request-header field is used with a method to make it conditional.
* If the requested resource has not been modified since the time specified in this field, the server SHOULD perform the
* requested operation as if the If-Unmodified-Since header were not present.
*
*
* If the requested variant has been modified since the specified time, the server MUST NOT perform the requested
* operation, and MUST return a 412 (Precondition Failed).
*
*
* If-Unmodified-Since = "If-Unmodified-Since" ":" HTTP-date
*
*
*
* An example of the field is:
*
* If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT
*
*
*
* If the request normally (i.e., without the If-Unmodified-Since header) would result in anything other than a 2xx or
* 412 status, the If-Unmodified-Since header SHOULD be ignored.
*
*
* If the specified date is invalid, the header is ignored.
*
*
* The result of a request having both an If-Unmodified-Since header field and either an If-None-Match or an
* If-Modified-Since header fields is undefined by this specification.
*
*
Additional Information
*
*/
public final class IfUnmodifiedSince extends HeaderDate {
/**
* Returns a parsed If-Unmodified-Since header.
*
* @param value The If-Unmodified-Since header string.
* @return The parsed If-Unmodified-Since header, or null if the string was null.
*/
public static IfUnmodifiedSince forString(String value) {
if (value == null)
return null;
return new IfUnmodifiedSince(value);
}
private IfUnmodifiedSince(String value) {
super(value);
}
}