Pub-Sub implements Observer pattern.Per my understanding Publisher is Subject and Subscribers are Observers. So publishers state change will be notified to Observers whenever there is a state change.
Do I need to implement any interface method for sending the message in the Subject (TopicPublisher) ?
Which is the right approach to implement the Observer (TopicSubscriber)?
Observer Class implements MessageListener's onMessage(message) (or) Observer Class implements NotificationListener's handleNotification(notification, callback)/