Configuring Topic - Hazelcast Reference Manual

To configure a topic, set the topic name, decide on statistics and global ordering, and set message listeners. Default values are:

global-ordering is false, meaning that by default, there is no guarantee of global order.
statistics is true, meaning that by default, statistics are calculated.

You can see the example configuration snippets below.

Declarative:

<hazelcast>
  ...
  <topic name="yourTopicName">
    <global-ordering-enabled>true</global-ordering-enabled>
    <statistics-enabled>true</statistics-enabled>
    <message-listeners>
      <message-listener>MessageListenerImpl</message-listener>
    </message-listeners>
  </topic>
  ...
</hazelcast>

Programmatic:

TopicConfig topicConfig = new TopicConfig();
topicConfig.setGlobalOrderingEnabled( true );
topicConfig.setStatisticsEnabled( true );
topicConfig.setName( "yourTopicName" );
MessageListener<String> implementation = new MessageListener<String>() {
  @Override
  public void onMessage( Message<String> message ) {
    // process the message
  }
};
topicConfig.addMessageListenerConfig( new ListenerConfig( implementation ) );
HazelcastInstance instance = Hazelcast.newHazelcastInstance()

Topic configuration has the following elements.

statistics-enabled: Default is true, meaning statistics are calculated.
global-ordering-enabled: Default is false, meaning there is no global order guarantee.
message-listeners: Lets you add listeners (listener classes) for the topic messages.

Besides the above elements, there are the following system properties that are topic related but not topic specific:

hazelcast.event.queue.capacity with a default value of 1,000,000
hazelcast.event.queue.timeout.millis with a default value of 250
hazelcast.event.thread.count with a default value of 5

For a description of these parameters, please see the Global Event Configuration section.

Distributed Data Structures Topic Configuring Topic