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1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *  
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *  
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License. 
18   *  
19   */
20  package org.apache.directory.api.ldap.model.message;
21  
22  
23  import java.util.Collection;
24  
25  
26  /**
27   * Represents a referral which is a set of alternative locations where an entry
28   * can be found. Here's what <a href="http://www.faqs.org/rfcs/rfc2251.html">
29   * RFC 2251 </a> has to say about it:
30   * 
31   * <pre>
32   *  4.1.11. Referral
33   * 
34   *   The referral error indicates that the contacted server does not hold
35   *   the target entry of the request.  The referral field is present in an
36   *   LDAPResult if the LDAPResult.resultCode field value is referral, and
37   *   absent with all other result codes.  It contains a reference to
38   *   another server (or set of servers) which may be accessed via LDAP or
39   *   other protocols.  Referrals can be returned in response to any
40   *   operation request (except unbind and abandon which do not have
41   *   responses). At least one URL MUST be present in the Referral.
42   * 
43   *   The referral is not returned for a singleLevel or wholeSubtree search
44   *   in which the search scope spans multiple naming contexts, and several
45   *   different servers would need to be contacted to complete the
46   *   operation. Instead, continuation references, described in section
47   *   4.5.3, are returned.
48   * 
49   *        Referral ::= SEQUENCE OF LDAPURL  -- one or more
50   * 
51   *        LDAPURL ::= LDAPString -- limited to characters permitted in URLs
52   * 
53   *   If the client wishes to progress the operation, it MUST follow the
54   *   referral by contacting any one of servers.  All the URLs MUST be
55   *   equally capable of being used to progress the operation.  (The
56   *   mechanisms for how this is achieved by multiple servers are outside
57   *   the scope of this document.)
58   * 
59   *   URLs for servers implementing the LDAP protocol are written according
60   *   to &lt;a href=&quot;http://www.faqs.org/rfcs/rfc2255.html&quot;&gt;[9]&lt;/a&gt;.  If an alias
61   *   was dereferenced, the &lt;dn&gt; part of the URL MUST be present, with the new
62   *   target object name.  If the &lt;dn&gt; part is present, the client MUST use this
63   *   name in its next request to progress the operation, and if it is not present
64   *   the client will use the same name as in the original request.  Some servers
65   *   (e.g. participating in distributed indexing) may provide a different filter
66   *   in a referral for a search operation.  If the filter part of the URL
67   *    is present in an LDAPURL, the client MUST use this filter in its next
68   *   request to progress this search, and if it is not present the client
69   *   MUST use the same filter as it used for that search.  Other aspects
70   *   of the new request may be the same or different as the request which
71   *   generated the referral.
72   * 
73   *   Note that UTF-8 characters appearing in a Dn or search filter may not
74   *   be legal for URLs (e.g. spaces) and MUST be escaped using the %
75   *   method in RFC 1738 &lt;a href=&quot;http://www.faqs.org/rfcs/rfc1738.html&quot;&gt;[7]&lt;/a&gt;.
76   * 
77   *   Other kinds of URLs may be returned, so long as the operation could
78   *   be performed using that protocol.
79   * </pre>
80   * 
81   * @author <a href="mailto:dev@directory.apache.org"> Apache Directory Project</a>
82   * TODO This interface should be located in a url package under common to be
83   *       constructed from a LDAPv3 URL parser. The interface will eventually
84   *       look very different once url support is added: for one it will add and
85   *       remove LdapUrl objects instead of strings or provide both string and
86   *       LdapUrl add/remove methods.
87   */
88  public interface Referral
89  {
90      /**
91       * Gets an unmodifiable set of alternative referral urls.
92       * 
93       * @return the alternative url objects.
94       */
95      Collection<String> getLdapUrls();
96  
97  
98      /**
99       * 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 }