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
015/**
016 * Represents a parsed <l>From</l> HTTP request header.
017 * 
018 * <p>
019 * The email address of the user making the request.
020 * 
021 * <h5 class='figure'>Example</h5>
022 * <p class='bcode'>
023 *    From: user@example.com
024 * </p>
025 * 
026 * <h5 class='topic'>RFC2616 Specification</h5>
027 * 
028 * The From request-header field, if given, SHOULD contain an Internet e-mail address for the human user who controls
029 * the requesting user agent.
030 * The address SHOULD be machine-usable, as defined by "mailbox" in RFC 822 [9] as updated by RFC 1123 [8]:
031 * 
032 * <p class='bcode'>
033 *    From   = "From" ":" mailbox
034 * </p>
035 * 
036 * <p>
037 * An example is:
038 * <p class='bcode'>
039 *    From: webmaster@w3.org
040 * </p>
041 * 
042 * <p>
043 * This header field MAY be used for logging purposes and as a means for identifying the source of invalid or unwanted
044 * requests.
045 * It SHOULD NOT be used as an insecure form of access protection.
046 * The interpretation of this field is that the request is being performed on behalf of the person given, who accepts
047 * responsibility for the method performed.
048 * In particular, robot agents SHOULD include this header so that the person responsible for running the robot can be
049 * contacted if problems occur on the receiving end.
050 * 
051 * <p>
052 * The Internet e-mail address in this field MAY be separate from the Internet host which issued the request.
053 * For example, when a request is passed through a proxy the original issuer's address SHOULD be used.
054 * 
055 * <p>
056 * The client SHOULD NOT send the From header field without the user's approval, as it might conflict with the user's
057 * privacy interests or their site's security policy.
058 * It is strongly recommended that the user be able to disable, enable, and modify the value of this field at any time
059 * prior to a request.
060 * 
061 * <h5 class='section'>See Also:</h5>
062 * <ul class='doctree'>
063 *    <li class='extlink'><a class='doclink' href='https://www.w3.org/Protocols/rfc2616/rfc2616.html'>Hypertext Transfer Protocol -- HTTP/1.1</a>
064 * </ul>
065 */
066public final class From extends HeaderString {
067
068   /**
069    * Returns a parsed <code>From</code> header.
070    * 
071    * @param value The <code>From</code> header string.
072    * @return The parsed <code>From</code> header, or <jk>null</jk> if the string was null.
073    */
074   public static From forString(String value) {
075      if (value == null)
076         return null;
077      return new From(value);
078   }
079
080   private From(String value) {
081      super(value);
082   }
083}