public interface EventContext extends Context
addNamingListener()
methods is referred
to as the target. 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.
If a service only supports registration for existing
targets, an attempt to register for a nonexistent target
results in a NameNotFoundException
being thrown as early as possible,
preferably at the time addNamingListener()
is called, or if that is
not possible, the listener will receive the exception through the
NamingExceptionEvent
.
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 NamingExceptionEvent
(containing a
NameNotFoundException
).
An application can use the method targetMustExist()
to check
whether a EventContext
supports registration
of nonexistent targets.
EventContext
instance on which you invoke the
registration methods is the event source of the events that are
(potentially) generated.
The source is not necessarily 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 EventContext
instance with which the listener
has registered.
For example, suppose a listener makes the following registration:
When an object named "x/y" is subsequently deleted, the correspondingNamespaceChangeListener listener = ...; src.addNamingListener("x", SUBTREE_SCOPE, listener);
NamingEvent
(evt
) must contain:
evt.getEventContext() == src evt.getOldBinding().getName().equals("x/y")
Furthermore, listener registration/deregistration is with
the EventContext
instance, 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 EventContext
instance on
which it invoked addNamingListener()
(just as
it needs to keep a reference to the listener in order to remove it
later). It cannot expect to do a lookup()
and get another instance of
a EventContext
on which to perform the deregistration.
removeNamingListener()
.
NamingExceptionEvent
.
Context.close()
is invoked on the EventContext
instance with which it has registered.
EventContext
instance that has outstanding
listeners will continue to exist and be maintained by the service provider.
NamingListener
. There are subinterfaces of NamingListener
for different of event types of NamingEvent
.
For example, the ObjectChangeListener
interface is for the NamingEvent.OBJECT_CHANGED
event type.
To register interest in multiple event types, the listener implementation
should implement multiple NamingListener
subinterfaces and use a
single invocation of addNamingListener()
.
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.
Context
instances in general, instances of
EventContext
are not guaranteed to be thread-safe.
Care must be taken when multiple threads are accessing the same
EventContext
concurrently.
See the
package description
for more information on threading issues.Modifier and Type | Field and Description |
---|---|
static int |
OBJECT_SCOPE
Constant for expressing interest in events concerning the object named
by the target.
|
static int |
ONELEVEL_SCOPE
Constant for expressing interest in events concerning objects
in the context named by the target,
excluding the context named by the target.
|
static int |
SUBTREE_SCOPE
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.
|
APPLET, AUTHORITATIVE, BATCHSIZE, DNS_URL, INITIAL_CONTEXT_FACTORY, LANGUAGE, OBJECT_FACTORIES, PROVIDER_URL, REFERRAL, SECURITY_AUTHENTICATION, SECURITY_CREDENTIALS, SECURITY_PRINCIPAL, SECURITY_PROTOCOL, STATE_FACTORIES, URL_PKG_PREFIXES
Modifier and Type | Method and Description |
---|---|
void |
addNamingListener(Name target,
int scope,
NamingListener l)
Adds a listener for receiving naming events fired
when the object(s) identified by a target and scope changes.
|
void |
addNamingListener(String target,
int scope,
NamingListener l)
Adds a listener for receiving naming events fired
when the object named by the string target name and scope changes.
|
void |
removeNamingListener(NamingListener l)
Removes a listener from receiving naming events fired
by this
EventContext . |
boolean |
targetMustExist()
Determines whether a listener can register interest in a target
that does not exist.
|
addToEnvironment, bind, bind, close, composeName, composeName, createSubcontext, createSubcontext, destroySubcontext, destroySubcontext, getEnvironment, getNameInNamespace, getNameParser, getNameParser, list, list, listBindings, listBindings, lookup, lookup, lookupLink, lookupLink, rebind, rebind, removeFromEnvironment, rename, rename, unbind, unbind
static final int OBJECT_SCOPE
The value of this constant is 0
.
static final int ONELEVEL_SCOPE
The value of this constant is 1
.
static final int SUBTREE_SCOPE
The value of this constant is 2
.
void addNamingListener(Name target, int scope, NamingListener l) throws NamingException
OBJECT_SCOPE
,
ONELEVEL_SCOPE
, and SUBTREE_SCOPE
to see how
scope
affects the registration.
target
needs to name a context only when scope
is
ONELEVEL_SCOPE
.
target
may name a non-context if scope
is either
OBJECT_SCOPE
or SUBTREE_SCOPE
. Using
SUBTREE_SCOPE
for a non-context might be useful,
for example, if the caller does not know in advance whether target
is a context and just wants to register interest in the (possibly
degenerate subtree) rooted at target
.
When the listener is notified of an event, the listener may
in invoked in a thread other than the one in which
addNamingListener()
is executed.
Care must be taken when multiple threads are accessing the same
EventContext
concurrently.
See the
package description
for more information on threading issues.
target
- A nonnull name to be resolved relative to this context.scope
- One of OBJECT_SCOPE
, ONELEVEL_SCOPE
, or
SUBTREE_SCOPE
.l
- The nonnull listener.NamingException
- If a problem was encountered while
adding the listener.removeNamingListener(javax.naming.event.NamingListener)
void addNamingListener(String target, int scope, NamingListener l) throws NamingException
Name
for details.target
- The nonnull string name of the object resolved relative
to this context.scope
- One of OBJECT_SCOPE
, ONELEVEL_SCOPE
, or
SUBTREE_SCOPE
.l
- The nonnull listener.NamingException
- If a problem was encountered while
adding the listener.removeNamingListener(javax.naming.event.NamingListener)
void removeNamingListener(NamingListener l) throws NamingException
EventContext
.
The listener may have registered more than once with this
EventContext
, perhaps with different target/scope arguments.
After this method is invoked, the listener will no longer
receive events with this EventContext
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 EventContext
instance, this method does not do anything.l
- The nonnull listener.NamingException
- If a problem was encountered while
removing the listener.addNamingListener(javax.naming.Name, int, javax.naming.event.NamingListener)
boolean targetMustExist() throws NamingException
NamingException
- If the context's behavior in this regard cannot
be determined. Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
Copyright © 1993, 2016, Oracle and/or its affiliates. All rights reserved.
DRAFT 9-internal+0-2016-01-26-133437.ivan.openjdk9onspinwait