Java tutorial
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If you don't indicate a single choice of license, a * recipient has the option to distribute your version of this file under * either the CDDL, the GPL Version 2 or to extend the choice of license to * its licensees as provided above. However, if you add GPL Version 2 code * and therefore, elected the GPL Version 2 license, then the option applies * only if the new code is made subject to such option by the copyright * holder. */ package javax.jms; /** A client uses a {@code TopicSubscriber} object to receive messages that * have been published to a topic. A {@code TopicSubscriber} object is the * publish/subscribe form of a message consumer. A {@code MessageConsumer} * can be created by using {@code Session.createConsumer}. * * <P>A {@code TopicSession} allows the creation of multiple * {@code 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. * * <P>Regular {@code TopicSubscriber} objects are not durable. They * receive only messages that are published while they are active. * * <P>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. * * <P>In some cases, a connection may both publish and subscribe to a topic. * The subscriber {@code NoLocal} attribute allows a subscriber to inhibit * the * delivery of messages published by its own connection. * * <P>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 {@code 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. * * <P>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 {@code TopicSubscriber} for a * particular durable subscription. * * <P>A client can change an existing durable subscription by creating a * durable {@code 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. * * <P>The {@code unsubscribe} method is used to delete a durable * subscription. The {@code unsubscribe} method can be used at the * {@code Session} or {@code TopicSession} level. * This method deletes the state being * maintained on behalf of the subscriber by its provider. * * <P>Creating a {@code MessageConsumer} provides the same features as * creating a {@code TopicSubscriber}. To create a durable subscriber, * use of {@code Session.CreateDurableSubscriber} is recommended. The * {@code TopicSubscriber} is provided to support existing code. * * @see javax.jms.Session#createConsumer * @see javax.jms.Session#createDurableSubscriber * @see javax.jms.TopicSession * @see javax.jms.TopicSession#createSubscriber * @see javax.jms.MessageConsumer * * @version JMS 2.0 * @since JMS 1.0 * */ public interface TopicSubscriber extends MessageConsumer { /** Gets the {@code Topic} associated with this subscriber. * * @return this subscriber's {@code Topic} * * @exception JMSException if the JMS provider fails to get the topic for * this topic subscriber * due to some internal error. */ Topic getTopic() throws JMSException; /** Gets the {@code NoLocal} attribute for this subscriber. * The default value for this attribute is false. * * @return true if locally published messages are being inhibited * * @exception JMSException if the JMS provider fails to get the * {@code NoLocal} attribute for * this topic subscriber * due to some internal error. */ boolean getNoLocal() throws JMSException; }