/* |
|
* Copyright (c) 1999, 2013, Oracle and/or its affiliates. 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. Oracle designates this |
|
* particular file as subject to the "Classpath" exception as provided |
|
* by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
|
* or visit www.oracle.com if you need additional information or have any |
|
* questions. |
|
*/ |
|
package javax.naming.event; |
|
import javax.naming.Name; |
|
import javax.naming.Context; |
|
import javax.naming.NamingException; |
|
/** |
|
* Contains methods for registering/deregistering listeners to be notified of |
|
* events fired when objects named in a context changes. |
|
* |
|
*<h1>Target</h1> |
|
* The name parameter in the <tt>addNamingListener()</tt> methods is referred |
|
* to as the <em>target</em>. The target, along with the scope, identify |
|
* the object(s) that the listener is interested in. |
|
* It is possible to register interest in a target that does not exist, but |
|
* there might be limitations in the extent to which this can be |
|
* supported by the service provider and underlying protocol/service. |
|
*<p> |
|
* If a service only supports registration for existing |
|
* targets, an attempt to register for a nonexistent target |
|
* results in a <tt>NameNotFoundException</tt> being thrown as early as possible, |
|
* preferably at the time <tt>addNamingListener()</tt> is called, or if that is |
|
* not possible, the listener will receive the exception through the |
|
* <tt>NamingExceptionEvent</tt>. |
|
*<p> |
|
* Also, for service providers that only support registration for existing |
|
* targets, when the target that a listener has registered for is |
|
* subsequently removed from the namespace, the listener is notified |
|
* via a <tt>NamingExceptionEvent</tt> (containing a |
|
*<tt>NameNotFoundException</tt>). |
|
*<p> |
|
* An application can use the method <tt>targetMustExist()</tt> to check |
|
* whether a <tt>EventContext</tt> supports registration |
|
* of nonexistent targets. |
|
* |
|
*<h1>Event Source</h1> |
|
* The <tt>EventContext</tt> instance on which you invoke the |
|
* registration methods is the <em>event source</em> of the events that are |
|
* (potentially) generated. |
|
* The source is <em>not necessarily</em> the object named by the target. |
|
* Only when the target is the empty name is the object named by the target |
|
* the source. |
|
* In other words, the target, |
|
* along with the scope parameter, are used to identify |
|
* the object(s) that the listener is interested in, but the event source |
|
* is the <tt>EventContext</tt> instance with which the listener |
|
* has registered. |
|
*<p> |
|
* For example, suppose a listener makes the following registration: |
|
*<blockquote><pre> |
|
* NamespaceChangeListener listener = ...; |
|
* src.addNamingListener("x", SUBTREE_SCOPE, listener); |
|
*</pre></blockquote> |
|
* When an object named "x/y" is subsequently deleted, the corresponding |
|
* <tt>NamingEvent</tt> (<tt>evt</tt>) must contain: |
|
*<blockquote><pre> |
|
* evt.getEventContext() == src |
|
* evt.getOldBinding().getName().equals("x/y") |
|
*</pre></blockquote> |
|
*<p> |
|
* Furthermore, listener registration/deregistration is with |
|
* the <tt>EventContext</tt> |
|
* <em>instance</em>, and not with the corresponding object in the namespace. |
|
* If the program intends at some point to remove a listener, then it needs to |
|
* keep a reference to the <tt>EventContext</tt> instance on |
|
* which it invoked <tt>addNamingListener()</tt> (just as |
|
* it needs to keep a reference to the listener in order to remove it |
|
* later). It cannot expect to do a <tt>lookup()</tt> and get another instance of |
|
* a <tt>EventContext</tt> on which to perform the deregistration. |
|
*<h1>Lifetime of Registration</h1> |
|
* A registered listener becomes deregistered when: |
|
*<ul> |
|
*<li>It is removed using <tt>removeNamingListener()</tt>. |
|
*<li>An exception is thrown while collecting information about the events. |
|
* That is, when the listener receives a <tt>NamingExceptionEvent</tt>. |
|
*<li><tt>Context.close()</tt> is invoked on the <tt>EventContext</tt> |
|
* instance with which it has registered. |
|
</ul> |
|
* Until that point, a <tt>EventContext</tt> instance that has outstanding |
|
* listeners will continue to exist and be maintained by the service provider. |
|
* |
|
*<h1>Listener Implementations</h1> |
|
* The registration/deregistration methods accept an instance of |
|
* <tt>NamingListener</tt>. There are subinterfaces of <tt>NamingListener</tt> |
|
* for different of event types of <tt>NamingEvent</tt>. |
|
* For example, the <tt>ObjectChangeListener</tt> |
|
* interface is for the <tt>NamingEvent.OBJECT_CHANGED</tt> event type. |
|
* To register interest in multiple event types, the listener implementation |
|
* should implement multiple <tt>NamingListener</tt> subinterfaces and use a |
|
* single invocation of <tt>addNamingListener()</tt>. |
|
* In addition to reducing the number of method calls and possibly the code size |
|
* of the listeners, this allows some service providers to optimize the |
|
* registration. |
|
* |
|
*<h1>Threading Issues</h1> |
|
* |
|
* Like <tt>Context</tt> instances in general, instances of |
|
* <tt>EventContext</tt> are not guaranteed to be thread-safe. |
|
* Care must be taken when multiple threads are accessing the same |
|
* <tt>EventContext</tt> concurrently. |
|
* See the |
|
* <a href=package-summary.html#THREADING>package description</a> |
|
* for more information on threading issues. |
|
* |
|
* @author Rosanna Lee |
|
* @author Scott Seligman |
|
* @since 1.3 |
|
*/ |
|
public interface EventContext extends Context { |
|
/** |
|
* Constant for expressing interest in events concerning the object named |
|
* by the target. |
|
*<p> |
|
* The value of this constant is <tt>0</tt>. |
|
*/ |
|
public final static int OBJECT_SCOPE = 0; |
|
/** |
|
* Constant for expressing interest in events concerning objects |
|
* in the context named by the target, |
|
* excluding the context named by the target. |
|
*<p> |
|
* The value of this constant is <tt>1</tt>. |
|
*/ |
|
public final static int ONELEVEL_SCOPE = 1; |
|
/** |
|
* Constant for expressing interest in events concerning objects |
|
* in the subtree of the object named by the target, including the object |
|
* named by the target. |
|
*<p> |
|
* The value of this constant is <tt>2</tt>. |
|
*/ |
|
public final static int SUBTREE_SCOPE = 2; |
|
/** |
|
* Adds a listener for receiving naming events fired |
|
* when the object(s) identified by a target and scope changes. |
|
* |
|
* The event source of those events is this context. See the |
|
* class description for a discussion on event source and target. |
|
* See the descriptions of the constants <tt>OBJECT_SCOPE</tt>, |
|
* <tt>ONELEVEL_SCOPE</tt>, and <tt>SUBTREE_SCOPE</tt> to see how |
|
* <tt>scope</tt> affects the registration. |
|
*<p> |
|
* <tt>target</tt> needs to name a context only when <tt>scope</tt> is |
|
* <tt>ONELEVEL_SCOPE</tt>. |
|
* <tt>target</tt> may name a non-context if <tt>scope</tt> is either |
|
* <tt>OBJECT_SCOPE</tt> or <tt>SUBTREE_SCOPE</tt>. Using |
|
* <tt>SUBTREE_SCOPE</tt> for a non-context might be useful, |
|
* for example, if the caller does not know in advance whether <tt>target</tt> |
|
* is a context and just wants to register interest in the (possibly |
|
* degenerate subtree) rooted at <tt>target</tt>. |
|
*<p> |
|
* When the listener is notified of an event, the listener may |
|
* in invoked in a thread other than the one in which |
|
* <tt>addNamingListener()</tt> is executed. |
|
* Care must be taken when multiple threads are accessing the same |
|
* <tt>EventContext</tt> concurrently. |
|
* See the |
|
* <a href=package-summary.html#THREADING>package description</a> |
|
* for more information on threading issues. |
|
* |
|
* @param target A nonnull name to be resolved relative to this context. |
|
* @param scope One of <tt>OBJECT_SCOPE</tt>, <tt>ONELEVEL_SCOPE</tt>, or |
|
* <tt>SUBTREE_SCOPE</tt>. |
|
* @param l The nonnull listener. |
|
* @exception NamingException If a problem was encountered while |
|
* adding the listener. |
|
* @see #removeNamingListener |
|
*/ |
|
void addNamingListener(Name target, int scope, NamingListener l) |
|
throws NamingException; |
|
/** |
|
* Adds a listener for receiving naming events fired |
|
* when the object named by the string target name and scope changes. |
|
* |
|
* See the overload that accepts a <tt>Name</tt> for details. |
|
* |
|
* @param target The nonnull string name of the object resolved relative |
|
* to this context. |
|
* @param scope One of <tt>OBJECT_SCOPE</tt>, <tt>ONELEVEL_SCOPE</tt>, or |
|
* <tt>SUBTREE_SCOPE</tt>. |
|
* @param l The nonnull listener. |
|
* @exception NamingException If a problem was encountered while |
|
* adding the listener. |
|
* @see #removeNamingListener |
|
*/ |
|
void addNamingListener(String target, int scope, NamingListener l) |
|
throws NamingException; |
|
/** |
|
* Removes a listener from receiving naming events fired |
|
* by this <tt>EventContext</tt>. |
|
* The listener may have registered more than once with this |
|
* <tt>EventContext</tt>, perhaps with different target/scope arguments. |
|
* After this method is invoked, the listener will no longer |
|
* receive events with this <tt>EventContext</tt> instance |
|
* as the event source (except for those events already in the process of |
|
* being dispatched). |
|
* If the listener was not, or is no longer, registered with |
|
* this <tt>EventContext</tt> instance, this method does not do anything. |
|
* |
|
* @param l The nonnull listener. |
|
* @exception NamingException If a problem was encountered while |
|
* removing the listener. |
|
* @see #addNamingListener |
|
*/ |
|
void removeNamingListener(NamingListener l) throws NamingException; |
|
/** |
|
* Determines whether a listener can register interest in a target |
|
* that does not exist. |
|
* |
|
* @return true if the target must exist; false if the target need not exist. |
|
* @exception NamingException If the context's behavior in this regard cannot |
|
* be determined. |
|
*/ |
|
boolean targetMustExist() throws NamingException; |
|
} |