1 /*
2 * Copyright (c) 1999, 2004, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.naming;
27
28 import java.util.Enumeration;
29
30 /**
31 * This interface is for enumerating lists returned by
32 * methods in the javax.naming and javax.naming.directory packages.
33 * It extends Enumeration to allow as exceptions to be thrown during
34 * the enumeration.
35 *<p>
36 * When a method such as list(), listBindings(), or search() returns
37 * a NamingEnumeration, any exceptions encountered are reserved until
38 * all results have been returned. At the end of the enumeration, the
39 * exception is thrown (by hasMore());
40 * <p>
41 * For example, if the list() is
42 * returning only a partial answer, the corresponding exception would
43 * be PartialResultException. list() would first return a NamingEnumeration.
44 * When the last of the results has been returned by the NamingEnumeration's
45 * next(), invoking hasMore() would result in PartialResultException being thrown.
46 *<p>
47 * In another example, if a search() method was invoked with a specified
48 * size limit of 'n'. If the answer consists of more than 'n' results,
49 * search() would first return a NamingEnumeration.
50 * When the n'th result has been returned by invoking next() on the
51 * NamingEnumeration, a SizeLimitExceedException would then thrown when
52 * hasMore() is invoked.
53 *<p>
54 * Note that if the program uses hasMoreElements() and nextElement() instead
55 * to iterate through the NamingEnumeration, because these methods
56 * cannot throw exceptions, no exception will be thrown. Instead,
57 * in the previous example, after the n'th result has been returned by
58 * nextElement(), invoking hasMoreElements() would return false.
59 *<p>
60 * Note also that NoSuchElementException is thrown if the program invokes
61 * next() or nextElement() when there are no elements left in the enumeration.
62 * The program can always avoid this exception by using hasMore() and
63 * hasMoreElements() to check whether the end of the enumeration has been reached.
64 *<p>
65 * If an exception is thrown during an enumeration,
66 * the enumeration becomes invalid.
67 * Subsequent invocation of any method on that enumeration
68 * will yield undefined results.
69 *
70 * @author Rosanna Lee
71 * @author Scott Seligman
72 *
73 * @see Context#list
74 * @see Context#listBindings
75 * @see javax.naming.directory.DirContext#search
76 * @see javax.naming.directory.Attributes#getAll
77 * @see javax.naming.directory.Attributes#getIDs
78 * @see javax.naming.directory.Attribute#getAll
79 * @since 1.3
80 */
81 public interface NamingEnumeration<T> extends Enumeration<T> {
82 /**
83 * Retrieves the next element in the enumeration.
84 * This method allows naming exceptions encountered while
85 * retrieving the next element to be caught and handled
86 * by the application.
87 * <p>
88 * Note that {@code next()} can also throw the runtime exception
89 * NoSuchElementException to indicate that the caller is
90 * attempting to enumerate beyond the end of the enumeration.
91 * This is different from a NamingException, which indicates
92 * that there was a problem in obtaining the next element,
93 * for example, due to a referral or server unavailability, etc.
94 *
95 * @return The possibly null element in the enumeration.
96 * null is only valid for enumerations that can return
97 * null (e.g. Attribute.getAll() returns an enumeration of
98 * attribute values, and an attribute value can be null).
99 * @exception NamingException If a naming exception is encountered while attempting
100 * to retrieve the next element. See NamingException
101 * and its subclasses for the possible naming exceptions.
102 * @exception java.util.NoSuchElementException If attempting to get the next element when none is available.
103 * @see java.util.Enumeration#nextElement
104 */
105 public T next() throws NamingException;
106
107 /**
108 * Determines whether there are any more elements in the enumeration.
109 * This method allows naming exceptions encountered while
110 * determining whether there are more elements to be caught and handled
111 * by the application.
112 *
113 * @return true if there is more in the enumeration ; false otherwise.
114 * @exception NamingException
115 * If a naming exception is encountered while attempting
116 * to determine whether there is another element
117 * in the enumeration. See NamingException
118 * and its subclasses for the possible naming exceptions.
119 * @see java.util.Enumeration#hasMoreElements
120 */
121 public boolean hasMore() throws NamingException;
122
123 /**
124 * Closes this enumeration.
125 *
126 * After this method has been invoked on this enumeration, the
127 * enumeration becomes invalid and subsequent invocation of any of
128 * its methods will yield undefined results.
129 * This method is intended for aborting an enumeration to free up resources.
130 * If an enumeration proceeds to the end--that is, until
131 * {@code hasMoreElements()} or {@code hasMore()} returns {@code false}--
132 * resources will be freed up automatically and there is no need to
133 * explicitly call {@code close()}.
134 *<p>
135 * This method indicates to the service provider that it is free
136 * to release resources associated with the enumeration, and can
137 * notify servers to cancel any outstanding requests. The {@code close()}
138 * method is a hint to implementations for managing their resources.
139 * Implementations are encouraged to use appropriate algorithms to
140 * manage their resources when client omits the {@code close()} calls.
141 *
142 * @exception NamingException If a naming exception is encountered
143 * while closing the enumeration.
144 * @since 1.3
145 */
146 public void close() throws NamingException;
147 }