Just Spring Integration

For the Curious: Endpoint API

Now that you have seen the basic types of consumers, you should understand where they are really used. Under normal circumstances, you do not have to use them, as you will be configuring them under an XML namespace. The framework provides these components under various namespaces, so you can add the respective elements declaratively straight out of the box. This reduces the amount of coding and encourages a declarative programming model.

But for now, keep in mind that Transformers, Filters, Routers, etc., are all supported by the spring XML namespace. This means you can declaratively create an instance of any of these flow components. For example, a transformer element is used to create a Transformer component which will fetch messages from the input channel to kick off the transformation.

Understanding the link between the classes and namespace elements will give us much more command of the framework. However, you are strongly encouraged to use namespaces to configure these endpoints, instead of using the API classes.

Consumers

If you recall from the earlier chapter on channels, there are two types of channels: one is pollable while the other is subscribable. Based on the same definition, we have two types of endpoint consumers: Polling Consumer and an Event-Driven Consumer.

A PollingConsumer polls the channel for messages based on a polling configuration. It is driven by the client program. The EventDrivenConsumer, on the other hand, subscribes to a subscribable ...