public interface TopicSubscriber extends MessageConsumer
TopicSubscriberobject to receive messages that have been published to a topic. A
TopicSubscriberobject is the publish/subscribe form of a message consumer. A
MessageConsumercan be created by using
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.
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 JMS 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.
unsubscribe method is used to delete a durable subscription. The
unsubscribe method can be used at the
TopicSession level. This method deletes the state being maintained on behalf of the subscriber by its provider.
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.
|Modifier and Type||Method and Description|
Topic getTopic() throws JMSException
Topicassociated with this subscriber.
JMSException- if the JMS provider fails to get the topic for this topic subscriber due to some internal error.
boolean getNoLocal() throws JMSException
NoLocalattribute for this subscriber. The default value for this attribute is false.
JMSException- if the JMS provider fails to get the
NoLocalattribute for this topic subscriber due to some internal error.