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 IMessageConsumer. The JMS server 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 an IMessageConsumer for a particular durable subscription.
A client can change an existing durable subscription by creating a durable IMessageConsumer 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.
ITopic to subscribe to An IMessageConsumer for the specified destination
Warning: Delete unused durable subscriptions using ISession.Unsubscribe. Unused durable subscriptions continue to accumulate topic messages as new messages are produced to the topic, even when no consumer is attached to the durable subscription; this consumes resources on the JMS server and can eventually lead to resource issues such as quota exceptions, or even out-of-memory, because no consumer is ever removing messages from the durable subscription.
| Exception Type | Condition |
|---|---|
| MessageException | if the session fails to create a subscriber due to some internal error. |
| InvalidDestinationException | if an invalid topic is specified. |
ISession Interface | WebLogic.Messaging Namespace | ISession. Overload List | Deleting durable subscriptions.