com.hazelcast.topic

Interface ITopic<E>

Type Parameters:

E - the type of the message

All Superinterfaces:

DistributedObject

public interface ITopic<E>
extends DistributedObject

Hazelcast provides distribution mechanism for publishing messages that are delivered to multiple subscribers, which is also known as a publish/subscribe (pub/sub) messaging model. Publish and subscriptions are cluster-wide.

When a member subscribes for a topic, it is actually registering for messages published by any member in the cluster, including the new members joined after you added the listener.

Messages are ordered, meaning that listeners(subscribers) will process the messages in the order they are actually published. If cluster member M publishes messages m1, m2, m3...mn to a topic T, then Hazelcast makes sure that all of the subscribers of topic T will receive and process m1, m2, m3...mn in order.

Since Hazelcast 3.5 it is possible to have reliable topics. Normally all topics rely on the shared eventing system and shared threads. With Hazelcast 3.5 it is possible to configure a topic to be reliable and to get its own Ringbuffer to store events and to get its own executor to process events. The events in the ringbuffer are replicated, so they won't get lost when a node goes down.

Method Summary

Modifier and Type	Method and Description
UUID	addMessageListener(MessageListener<E> listener) Subscribes to this topic.
LocalTopicStats	getLocalTopicStats() Returns statistics about this topic, like total number of publishes/receives.
String	getName() Returns the name of this ITopic instance.
void	publish(E message) Publishes the message to all subscribers of this topic.
boolean	removeMessageListener(UUID registrationId) Stops receiving messages for the given message listener.

Methods inherited from interface com.hazelcast.core.DistributedObject

destroy, getPartitionKey, getServiceName

Method Detail

getName

String getName()

Returns the name of this ITopic instance.

Specified by:

getName in interface DistributedObject

Returns:

name of this ITopic instance

publish

void publish(@Nonnull
             E message)

Publishes the message to all subscribers of this topic.

Parameters:

message - the message to publish to all subscribers of this topic

Throws:

TopicOverloadException - if the consumer is too slow (only works in combination with reliable topic)

addMessageListener

@Nonnull
UUID addMessageListener(@Nonnull
                                 MessageListener<E> listener)

Subscribes to this topic. When a message is published, the MessageListener.onMessage(Message) method of the given MessageListener is called. More than one message listener can be added on one instance. See ReliableMessageListener to better integrate with a reliable topic.

Parameters:

listener - the MessageListener to add

Returns:

returns the registration ID

Throws:

NullPointerException - if listener is null

removeMessageListener

boolean removeMessageListener(@Nonnull
                              UUID registrationId)

Stops receiving messages for the given message listener.

If the given listener already removed, this method does nothing.

Parameters:

registrationId - ID of listener registration

Returns:

true if registration is removed, false otherwise

getLocalTopicStats

@Nonnull
LocalTopicStats getLocalTopicStats()

Returns statistics about this topic, like total number of publishes/receives. The statistics are local to this member and represent the activity on this member, not the entire cluster.

Returns:

statistics about this topic