public interface TopicSubscriber extends MessageConsumer
TopicSubscriber
object to receive messages that have been published to a topic. A
TopicSubscriber
object is the publish/subscribe form of a message consumer. A MessageConsumer
can be
created by using Session.createConsumer
.
A TopicSession
allows the creation of multiple TopicSubscriber
objects per topic. It will deliver
each message for a topic to each subscriber eligible to receive it. Each copy of the message is treated as a
completely separate message. Work done on one copy has no effect on the others; acknowledging one does not
acknowledge the others; one message may be delivered immediately, while another waits for its subscriber to process
messages ahead of it.
Regular TopicSubscriber
objects are not durable. They receive only messages that are published while they are
active.
Messages filtered out by a subscriber's message selector will never be delivered to the subscriber. From the subscriber's perspective, they do not exist.
In some cases, a connection may both publish and subscribe to a topic. The subscriber NoLocal
attribute
allows a subscriber to inhibit the delivery of messages published by its own connection.
If a client needs to receive all the messages published on a topic, including the ones published while the subscriber
is inactive, it uses a durable TopicSubscriber
. The Jakarta Messaging provider retains a record of this durable
subscription and insures that all messages from the topic's publishers are retained until they are acknowledged by
this durable subscriber or they have expired.
Sessions with durable subscribers must always provide the same client identifier. In addition, each client must
specify a name that uniquely identifies (within client identifier) each durable subscription it creates. Only one
session at a time can have a TopicSubscriber
for a particular durable subscription.
A client can change an existing durable subscription by creating a durable TopicSubscriber
with the same name
and a new topic and/or message selector. Changing a durable subscription is equivalent to unsubscribing (deleting)
the old one and creating a new one.
The unsubscribe
method is used to delete a durable subscription. The unsubscribe
method can be used
at the Session
or TopicSession
level. This method deletes the state being maintained on behalf of the
subscriber by its provider.
Creating a MessageConsumer
provides the same features as creating a TopicSubscriber
. To create a
durable subscriber, use of Session.CreateDurableSubscriber
is recommended. The TopicSubscriber
is
provided to support existing code.
Session.createConsumer(javax.jms.Destination)
,
Session.createDurableSubscriber(javax.jms.Topic, java.lang.String)
,
TopicSession
,
TopicSession.createSubscriber(javax.jms.Topic)
,
MessageConsumer
Modifier and Type | Method and Description |
---|---|
boolean |
getNoLocal()
Gets the
NoLocal attribute for this subscriber. |
Topic |
getTopic()
Gets the
Topic associated with this subscriber. |
close, getMessageListener, getMessageSelector, receive, receive, receiveNoWait, setMessageListener
Topic getTopic() throws JMSException
Topic
associated with this subscriber.Topic
JMSException
- if the Jakarta Messaging provider fails to get the topic for this topic subscriber due to some internal
error.boolean getNoLocal() throws JMSException
NoLocal
attribute for this subscriber. The default value for this attribute is false.JMSException
- if the Jakarta Messaging provider fails to get the NoLocal
attribute for this topic subscriber due
to some internal error.Copyright © 2020 JBoss by Red Hat. All rights reserved.