KMTopicSession Class Reference
Overview
A TopicSession object provides methods for creating TopicPublisher, TopicSubscriber, and TemporaryTopic objects. It also provides a method for deleting its client’s durable subscribers.
KMTopicSession is a JMS 1.0 API. KMSession should be used instead.
A TopicSession is used for creating Pub/Sub specific objects. In general, use the Session object, and use TopicSession only to support existing code. Using the Session object simplifies the programming model, and allows transactions to be used across the two messaging domains.
A TopicSession cannot be used to create objects specific to the point-to-point domain. The following methods inherit from Session, but must throw an KMIllegalStateException if used from TopicSession:
- createBrowser
- createQueue
- createTemporaryQueue
Tasks
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– createTopic:
Creates a topic identity given a Topic name.
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– createSubscriber:
Creates a nondurable subscriber to the specified topic.
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– createSubscriber:messageSelector:noLocal:
Creates a nondurable subscriber to the specified topic, using a message selector or specifying whether messages published by its own connection should be delivered to it.
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– createDurableSubscriber:name:
Creates a durable subscriber to the specified topic.
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– createDurableSubscriber:name:messageSelector:noLocal:
Creates a durable subscriber to the specified topic, using a message selector or specifying whether messages published by its own connection should be delivered to it.
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– createPublisher:
Creates a publisher for the specified topic.
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– createTemporaryTopic
Creates a TemporaryTopic object. Its lifetime will be that of the TopicConnection unless it is deleted earlier.
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– unsubscribe:
Unsubscribes a durable subscription that has been created by a client.
Instance Methods
createDurableSubscriber:name:
Creates a durable subscriber to the specified topic.
- (KMTopicSubscriber *)createDurableSubscriber:(KMTopic *)topic name:(NSString *)name
Parameters
- topic
the non-temporary Topic to subscribe to
- name
the name used to identify this subscription
Discussion
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 subscriber is equivalent to unsubscribing (deleting) the old one and creating a new one.
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. The default value for this attribute is false.
Exceptions
- KMJMSException
if the session fails to create a subscriber due to some internal error.
- KMInvalidDestinationException
if an invalid topic is specified.
Declared In
KMTopicSession.h
createDurableSubscriber:name:messageSelector:noLocal:
Creates a durable subscriber to the specified topic, using a message selector or specifying whether messages published by its own connection should be delivered to it.
- (KMTopicSubscriber *)createDurableSubscriber:(KMTopic *)topic name:(NSString *)name messageSelector:(NSString *)messageSelector noLocal:(BOOL)noLocal
Parameters
- topic
the non-temporary Topic to subscribe to
- name
the name used to identify this subscription
- messageSelector
only messages with properties matching the message selector expression are delivered. A value of null or an empty string indicates that there is no message selector for the message consumer.
- noLocal
if set, inhibits the delivery of messages published by its own connection
Discussion
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 which 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. An inactive durable subscriber is one that exists but does not currently have a message consumer associated with it.
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 subscriber is equivalent to unsubscribing (deleting) the old one and creating a new one.
Exceptions
- KMJMSException
if the session fails to create a subscriber due to some internal error.
- KMInvalidDestinationException
if an invalid topic is specified.
- KMInvalidSelectorException
if the message selector is invalid.
Declared In
KMTopicSession.h
createPublisher:
Creates a publisher for the specified topic.
- (KMTopicPublisher *)createPublisher:(KMTopic *)topic
Parameters
- topic
the Topic to publish to, or null if this is an unidentified producer
Discussion
A client uses a TopicPublisher object to publish messages on a topic. Each time a client creates a TopicPublisher on a topic, it defines a new sequence of messages that have no ordering relationship with the messages it has previously sent.
Exceptions
- KMJMSException
if the session fails to create a publisher due to some internal error.
- KMInvalidDestinationException
if an invalid topic is specified.
Declared In
KMTopicSession.h
createSubscriber:
Creates a nondurable subscriber to the specified topic.
- (KMTopicSubscriber *)createSubscriber:(KMTopic *)topic
Parameters
- topic
the Topic to subscribe to
Discussion
A client uses a TopicSubscriber object to receive messages that have been published to a topic.
Regular TopicSubscriber objects are not durable. They receive only messages that are published while they are active.
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. The default value for this attribute is false.
Exceptions
- KMJMSException
if the session fails to create a subscriber due to some internal error.
- KMInvalidDestinationException
if an invalid topic is specified.
Declared In
KMTopicSession.h
createSubscriber:messageSelector:noLocal:
Creates a nondurable subscriber to the specified topic, using a message selector or specifying whether messages published by its own connection should be delivered to it.
- (KMTopicSubscriber *)createSubscriber:(KMTopic *)topic messageSelector:(NSString *)messageSelector noLocal:(BOOL)noLocal
Parameters
- topic
the Topic to subscribe to
- messageSelector
only messages with properties matching the message selector expression are delivered. A value of null or an empty string indicates that there is no message selector for the message consumer.
- noLocal
if set, inhibits the delivery of messages published by its own connection
Discussion
A client uses a TopicSubscriber object to receive messages that have been published to a topic.
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. The default value for this attribute is false.
Exceptions
- KMJMSException
if the session fails to create a subscriber due to some internal error.
- KMInvalidDestinationException
if an invalid topic is specified.
- KMInvalidSelectorException
if the message selector is invalid.
Declared In
KMTopicSession.h
createTemporaryTopic
Creates a TemporaryTopic object. Its lifetime will be that of the TopicConnection unless it is deleted earlier.
- (KMTemporaryTopic *)createTemporaryTopic
Return Value
a temporary topic identity
Exceptions
- KMJMSException
if the session fails to create a temporary topic due to some internal error.
Declared In
KMTopicSession.h
createTopic:
Creates a topic identity given a Topic name.
- (KMTopic *)createTopic:(NSString *)topicName
Parameters
- topicName
the name of this Topic
Return Value
a Topic with the given name
Discussion
This facility is provided for the rare cases where clients need to dynamically manipulate topic identity. This allows the creation of a topic identity with a provider-specific name. Clients that depend on this ability are not portable.
Note that this method is not for creating the physical topic. The physical creation of topics is an administrative task and is not to be initiated by the JMS API. The one exception is the creation of temporary topics, which is accomplished with the createTemporaryTopic method.
Exceptions
- KMJMSException
if the session fails to create a topic due to some internal error.
Declared In
KMTopicSession.h
unsubscribe:
Unsubscribes a durable subscription that has been created by a client.
- (void)unsubscribe:(NSString *)name
Parameters
- name
the name used to identify this subscription
Discussion
This method deletes the state being maintained on behalf of the subscriber by its provider.A
It is erroneous for a client to delete a durable subscription while there is an active TopicSubscriber for the subscription, or while a consumed message is part of a pending transaction or has not been acknowledged in the session.
Exceptions
- KMJMSException
if the session fails to unsubscribe to the durable subscription due to some internal error.
- KMInvalidDestinationException
if an invalid subscription name is specified.
Declared In
KMTopicSession.h