001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *  
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *  
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License. 
018 *  
019 */
020package org.apache.directory.api.ldap.model.message;
021
022
023import java.util.Collection;
024
025
026/**
027 * Represents a referral which is a set of alternative locations where an entry
028 * can be found. Here's what <a href="http://www.faqs.org/rfcs/rfc2251.html">
029 * RFC 2251 </a> has to say about it:
030 * 
031 * <pre>
032 *  4.1.11. Referral
033 * 
034 *   The referral error indicates that the contacted server does not hold
035 *   the target entry of the request.  The referral field is present in an
036 *   LDAPResult if the LDAPResult.resultCode field value is referral, and
037 *   absent with all other result codes.  It contains a reference to
038 *   another server (or set of servers) which may be accessed via LDAP or
039 *   other protocols.  Referrals can be returned in response to any
040 *   operation request (except unbind and abandon which do not have
041 *   responses). At least one URL MUST be present in the Referral.
042 * 
043 *   The referral is not returned for a singleLevel or wholeSubtree search
044 *   in which the search scope spans multiple naming contexts, and several
045 *   different servers would need to be contacted to complete the
046 *   operation. Instead, continuation references, described in section
047 *   4.5.3, are returned.
048 * 
049 *        Referral ::= SEQUENCE OF LDAPURL  -- one or more
050 * 
051 *        LDAPURL ::= LDAPString -- limited to characters permitted in URLs
052 * 
053 *   If the client wishes to progress the operation, it MUST follow the
054 *   referral by contacting any one of servers.  All the URLs MUST be
055 *   equally capable of being used to progress the operation.  (The
056 *   mechanisms for how this is achieved by multiple servers are outside
057 *   the scope of this document.)
058 * 
059 *   URLs for servers implementing the LDAP protocol are written according
060 *   to &lt;a href=&quot;http://www.faqs.org/rfcs/rfc2255.html&quot;&gt;[9]&lt;/a&gt;.  If an alias
061 *   was dereferenced, the &lt;dn&gt; part of the URL MUST be present, with the new
062 *   target object name.  If the &lt;dn&gt; part is present, the client MUST use this
063 *   name in its next request to progress the operation, and if it is not present
064 *   the client will use the same name as in the original request.  Some servers
065 *   (e.g. participating in distributed indexing) may provide a different filter
066 *   in a referral for a search operation.  If the filter part of the URL
067 *    is present in an LDAPURL, the client MUST use this filter in its next
068 *   request to progress this search, and if it is not present the client
069 *   MUST use the same filter as it used for that search.  Other aspects
070 *   of the new request may be the same or different as the request which
071 *   generated the referral.
072 * 
073 *   Note that UTF-8 characters appearing in a Dn or search filter may not
074 *   be legal for URLs (e.g. spaces) and MUST be escaped using the %
075 *   method in RFC 1738 &lt;a href=&quot;http://www.faqs.org/rfcs/rfc1738.html&quot;&gt;[7]&lt;/a&gt;.
076 * 
077 *   Other kinds of URLs may be returned, so long as the operation could
078 *   be performed using that protocol.
079 * </pre>
080 * 
081 * @author <a href="mailto:dev@directory.apache.org"> Apache Directory Project</a>
082 * TODO This interface should be located in a url package under common to be
083 *       constructed from a LDAPv3 URL parser. The interface will eventually
084 *       look very different once url support is added: for one it will add and
085 *       remove LdapUrl objects instead of strings or provide both string and
086 *       LdapUrl add/remove methods.
087 */
088public interface Referral
089{
090    /**
091     * Gets an unmodifiable set of alternative referral urls.
092     * 
093     * @return the alternative url objects.
094     */
095    Collection<String> getLdapUrls();
096
097
098    /**
099     * Gets an unmodifiable set of encoded referral urls.
100     * 
101     * @return the encoded url objects.
102     */
103    Collection<byte[]> getLdapUrlsBytes();
104
105
106    /**
107     * Adds an LDAPv3 URL to this Referral.
108     * 
109     * @param url
110     *            the LDAPv3 URL to add
111     */
112    void addLdapUrl( String url );
113
114
115    /**
116     * Adds an encoded LDAPv3 URL to this Referral.
117     * 
118     * @param urlBytes the encoded LDAPv3 URL to add
119     */
120    void addLdapUrlBytes( byte[] urlBytes );
121
122
123    /**
124     * Removes an LDAPv3 URL to this Referral.
125     * 
126     * @param url
127     *            the LDAPv3 URL to remove
128     */
129    void removeLdapUrl( String url );
130
131
132    /**
133     * @return The total length of the Referral
134     */
135    int getReferralLength();
136
137
138    /**
139     * Set the length of the referral
140     * @param referralLength The total length of the Referral
141     */
142    void setReferralLength( int referralLength );
143}