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- All Superinterfaces:
AutoCloseable
,MessageConsumer
public interface TopicSubscriber extends MessageConsumer
A client uses aTopicSubscriber
object to receive messages that have been published to a topic. ATopicSubscriber
object is the publish/subscribe form of a message consumer. AMessageConsumer
can be created by usingSession.createConsumer
.A
TopicSession
allows the creation of multipleTopicSubscriber
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. Theunsubscribe
method can be used at theSession
orTopicSession
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 aTopicSubscriber
. To create a durable subscriber, use ofSession.CreateDurableSubscriber
is recommended. TheTopicSubscriber
is provided to support existing code.- Since:
- JMS 1.0
- Version:
- Jakarta Messaging 2.0
- See Also:
Session.createConsumer(jakarta.jms.Destination)
,Session.createDurableSubscriber(jakarta.jms.Topic, java.lang.String)
,TopicSession
,TopicSession.createSubscriber(jakarta.jms.Topic)
,MessageConsumer
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description boolean
getNoLocal()
Gets theNoLocal
attribute for this subscriber.Topic
getTopic()
Gets theTopic
associated with this subscriber.-
Methods inherited from interface jakarta.jms.MessageConsumer
close, getMessageListener, getMessageSelector, receive, receive, receiveNoWait, setMessageListener
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Method Detail
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getTopic
Topic getTopic() throws JMSException
Gets theTopic
associated with this subscriber.- Returns:
- this subscriber's
Topic
- Throws:
JMSException
- if the Jakarta Messaging provider fails to get the topic for this topic subscriber due to some internal error.
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getNoLocal
boolean getNoLocal() throws JMSException
Gets theNoLocal
attribute for this subscriber. The default value for this attribute is false.- Returns:
- true if locally published messages are being inhibited
- Throws:
JMSException
- if the Jakarta Messaging provider fails to get theNoLocal
attribute for this topic subscriber due to some internal error.
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