view src/share/classes/javax/naming/event/package.html @ 0:37a05a11f281

Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children 00cd9dc3c2b5
line wrap: on
line source
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<head>
<!--
Copyright 1999-2006 Sun Microsystems, Inc.  All Rights Reserved.
DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

This code is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License version 2 only, as
published by the Free Software Foundation.  Sun designates this
particular file as subject to the "Classpath" exception as provided
by Sun in the LICENSE file that accompanied this code.

This code is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
version 2 for more details (a copy is included in the LICENSE file that
accompanied this code).

You should have received a copy of the GNU General Public License version
2 along with this work; if not, write to the Free Software Foundation,
Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
CA 95054 USA or visit www.sun.com if you need additional information or
have any questions.
-->
</head>
<body bgcolor="white">

Provides support for event notification when accessing naming and
directory services.

<p>
This package defines the event notification operations of the Java Naming
and Directory Interface<font size=-2><sup>TM</sup></font> (JNDI). &nbsp;
JNDI provides naming and directory functionality to applications
written in the Java programming language.  It is designed to be
independent of any specific naming or directory service
implementation.  Thus a variety of services--new, emerging, and
already deployed ones--can be accessed in a common way.

<h4>Naming Events</h4>
<p>
This package defines a <tt>NamingEvent</tt> class to represent an event
that is generated by a naming/directory service.
It also defines subinterfaces of <tt>Context</tt> and <tt>DirContext</tt>,
called <tt>EventContext</tt> and <tt>EventDirContext</tt>,
through which applications can register their interest in events
fired by the context.
<p>
<tt>NamingEvent</tt> represents an event that occurs in a 
naming or directory service. There are two categories of naming events:
<ul>
<li>Those that affect the namespace (add/remove/rename an object)
<li>Those that affect the objects' contents.
</ul>
Each category of events is handled by a corresponding listener:
<tt>NamespaceChangeListener</tt>, <tt>ObjectChangeListener</tt>.
<p>
An application, for example, can register its interest in changes to
objects in a context as follows:
<blockquote>
<pre>
EventContext src = 
    (EventContext)(new InitialContext()).lookup("o=wiz,c=us");
src.addNamingListener("ou=users", EventContext.ONELEVEL_SCOPE,
    new ChangeHandler());
...
class ChangeHandler implements ObjectChangeListener {
    public void objectChanged(NamingEvent evt) {
        System.out.println(evt.getNewBinding());
    }
    public void namingExceptionThrown(NamingExceptionEvent evt) {
        System.out.println(evt.getException());
    }
}
</pre>
</blockquote>

<a name=THREADING></a>
<h4>Threading Issues</h4>

When an event is dispatched to a listener, the listener method (such
as <tt>objectChanged()</tt>) may be executed in a thread other than the
one in which the call to <tt>addNamingListener()</tt> was executed.
The choice of which thread to use is made by the service provider.
When an event is dispatched to multiple listeners, the service provider
may choose (and is generally encouraged) to execute the listener methods
concurrently in separate threads.
<p>
When a listener instance invokes <tt>NamingEvent.getEventContext()</tt>,
it must take into account the possibility that other threads will be
working with that context concurrently.  Likewise, when a listener is
registered via <tt>addNamingListener()</tt>, the registering thread
must take into account the likely possibility that the service provider
will later invoke the listeners in newly-created threads.  As <tt>Context</tt>
instances are not guaranteed to be thread-safe in general, all context
operations must be synchronized as needed.

<h4>Exception Handling</h4>

When a listener registers for events with a context, the context might
need to do some internal processing in order to collect information
required to generate the events.  The context, for example, might need
to make a request to the server to register interest in changes
on the server that will eventually be translated into events.
If an exception occurs that prevents information about the events from
being collected, the listener will never be notified of the events.
When such an exception occurs, a <tt>NamingExceptionEvent</tt> is
fired to notify the listener. The listener's
<tt>namingExceptionThrown()</tt> method is invoked, as shown in the 
sample code above,
and the listener is automatically deregistered.
<p>

<h2>Package Specification</h2>


The JNDI API Specification and related documents can be found in the
<a href="../../../../technotes/guides/jndi/index.html">JNDI documentation</a>.

@since 1.3

</body>
</html>