Just Spring Integration by Madhusudhan Konda

Author:Madhusudhan Konda [Madhusudhan Konda]
Language: eng
Format: epub, pdf
Tags: COMPUTERS / Programming Languages / Java
ISBN: 9781449316075
Publisher: O'Reilly Media
Published: 2012-04-01T16:00:00+00:00

Event-Driven Consumers

The second type of endpoint consumers that subscribe rather than poll to the message stream is categorized as Event-Driven Consumers. The framework defines this type of consumer as an EventDrivenConsumer class. Their fundamental characteristic is that they wait for someone (the framework’s responsibility) to deliver the message as soon as it appears on the channel. From our earlier discussions on event messages, you know that SubscribableChannel supports this type of consumer.

The instantiation of this consumer is exactly like that of PollingConsumer—supply a channel to which it should subscribe to get a message stream and a handler to handle the messages.

private EventDrivenConsumer consumer = null; private PositionsHandler positionsHandler = null; private ApplicationContext ctx = null; public PositionsEventDrivenConsumer(ApplicationContext ctx, PublishSubscribeChannel positionsChannel) { positionsHandler = new PositionsHandler(); // instantiate the event driven consumer consumer = new EventDrivenConsumer(positionsChannel, positionsHandler); consumer.setBeanFactory(ctx);

The PositionsHandler is a simple class that implements MessageHandler with providing the handleMessage method. Starting the consumer is as simple as calling the start method on the EventDrivenConsumer:

public void startConsumer() { // EventDrivenConsumer exposes start method consumer.start(); }

Unless you have a compelling requirement, use EventDrivenConsumer.

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