When using the callback model, you must register a general callback object for each Broker client by calling the BrokerClient.registerCallback method. When an event is received, if there are no specific callback objects registered which match the event's subscription identifier or tag, the general callback object's handleBrokerEvent method will be invoked to handle the event.

You can have a single callback object process all of your application's events by making a separate BrokerClient.registerCallback call for each BrokerClient that your application uses, specifying the same callback object each time.

Depending on the complexity of your design, you might find that a single, general callback object is all that your client application requires.