1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> 2 <html> 3 <head> 4 <!-- 5 Copyright (c) 1999, 2019, Oracle and/or its affiliates. All rights reserved. 6 DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 7 8 This code is free software; you can redistribute it and/or modify it 9 under the terms of the GNU General Public License version 2 only, as 10 published by the Free Software Foundation. Oracle designates this 11 particular file as subject to the "Classpath" exception as provided 12 by Oracle in the LICENSE file that accompanied this code. 13 14 This code is distributed in the hope that it will be useful, but WITHOUT 15 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17 version 2 for more details (a copy is included in the LICENSE file that 18 accompanied this code). 19 20 You should have received a copy of the GNU General Public License version 21 2 along with this work; if not, write to the Free Software Foundation, 22 Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 23 24 Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 25 or visit www.oracle.com if you need additional information or have any 26 questions. 27 --> 28 </head> 29 <body bgcolor="white"> 30 31 Provides support for event notification when accessing naming and 32 directory services. 33 34 <p> 35 This package defines the event notification operations of the Java Naming 36 and Directory Interface (JNDI). 37 JNDI provides naming and directory functionality to applications 38 written in the Java programming language. It is designed to be 39 independent of any specific naming or directory service 40 implementation. Thus a variety of services--new, emerging, and 41 already deployed ones--can be accessed in a common way. 42 43 <h2>Naming Events</h2> 44 <p> 45 This package defines a <code>NamingEvent</code> class to represent an event 46 that is generated by a naming/directory service. 47 It also defines subinterfaces of <code>Context</code> and <code>DirContext</code>, 48 called <code>EventContext</code> and <code>EventDirContext</code>, 49 through which applications can register their interest in events 50 fired by the context. 51 <p> 52 <code>NamingEvent</code> represents an event that occurs in a 53 naming or directory service. There are two categories of naming events: 54 <ul> 55 <li>Those that affect the namespace (add/remove/rename an object) 56 <li>Those that affect the objects' contents. 57 </ul> 58 Each category of events is handled by a corresponding listener: 59 <code>NamespaceChangeListener</code>, <code>ObjectChangeListener</code>. 60 <p> 61 An application, for example, can register its interest in changes to 62 objects in a context as follows: 63 <blockquote> 64 <pre> 65 EventContext src = 66 (EventContext)(new InitialContext()).lookup("o=wiz,c=us"); 67 src.addNamingListener("ou=users", EventContext.ONELEVEL_SCOPE, 68 new ChangeHandler()); 69 ... 70 class ChangeHandler implements ObjectChangeListener { 71 public void objectChanged(NamingEvent evt) { 72 System.out.println(evt.getNewBinding()); 73 } 74 public void namingExceptionThrown(NamingExceptionEvent evt) { 75 System.out.println(evt.getException()); 76 } 77 } 78 </pre> 79 </blockquote> 80 81 <a id=THREADING></a> 82 <h3>Threading Issues</h3> 83 84 When an event is dispatched to a listener, the listener method (such 85 as <code>objectChanged()</code>) may be executed in a thread other than the 86 one in which the call to <code>addNamingListener()</code> was executed. 87 The choice of which thread to use is made by the service provider. 88 When an event is dispatched to multiple listeners, the service provider 89 may choose (and is generally encouraged) to execute the listener methods 90 concurrently in separate threads. 91 <p> 92 When a listener instance invokes <code>NamingEvent.getEventContext()</code>, 93 it must take into account the possibility that other threads will be 94 working with that context concurrently. Likewise, when a listener is 95 registered via <code>addNamingListener()</code>, the registering thread 96 must take into account the likely possibility that the service provider 97 will later invoke the listeners in newly-created threads. As <code>Context</code> 98 instances are not guaranteed to be thread-safe in general, all context 99 operations must be synchronized as needed. 100 101 <h3>Exception Handling</h3> 102 103 When a listener registers for events with a context, the context might 104 need to do some internal processing in order to collect information 105 required to generate the events. The context, for example, might need 106 to make a request to the server to register interest in changes 107 on the server that will eventually be translated into events. 108 If an exception occurs that prevents information about the events from 109 being collected, the listener will never be notified of the events. 110 When such an exception occurs, a <code>NamingExceptionEvent</code> is 111 fired to notify the listener. The listener's 112 <code>namingExceptionThrown()</code> method is invoked, as shown in the 113 sample code above, 114 and the listener is automatically deregistered. 115 116 <h2>Package Specification</h2> 117 118 119 The JNDI API Specification and related documents can be found in the 120 {@extLink jndi_overview JNDI documentation}. 121 122 @since 1.3 123 124 </body> 125 </html>