Introducing Spring Framework

Chapter 11 ■ Integrating Your Spring Application with External Systems
Listing 11-13 shows the tag that allows you to consume messages from RabbitMQ
through the rabbitmqConsumer component. Listing 11-14 shows the RabbitMQ consumer.
Listing 11-14. RabbitMQConsumer.java
package com.apress.isf.spring.amqp;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageListener;
import org.springframework.stereotype.Component;
import com.apress.isf.java.model.Document;
import com.apress.isf.java.utils.XmlUtils;
@Component("rabbitmqConsumer")
public class RabbitMQConsumer implements MessageListener {
private static final Logger log = LoggerFactory.getLogger(RabbitMQConsumer.class);
}
@Override
public void onMessage(Message message) {
Document document = XmlUtils.fromXML(new String(message.getBody()),Document.class);
log.debug("Document received: " + document);
}
In Listing 11-14, you are using the org.springframework.amqp.core.MessageListener class by implementing
its method onMessage(Message message), so every time there is a new message on RabbitMQ and in the
mydocumentsQueue, this method will receive the message. Take a look at this method; its parameter is a
org.springframework.amqp.core.Message class, so it will be necessary to convert it back from the array of bytes[]
to XML String and from XML String to a Document object. Now if you run Listing 11-12 again, you should get output
saying Document received!
■ ■Note The book’s companion source code contains all the dependencies (through gradle) used in this chapter.
Summary
In this chapter, you saw how you can interact and integrate your application between external systems. The Spring
Framework provides useful extensions to do these integrations: the JMS and the AMQP. But that’s not all; Spring
also provides the Spring Integration module that facilitates even more of the integration between systems, requiring
minimal or even zero code! Apress has an excellent book called Pro Spring Integration written by the creators of this
extension.
In the next chapter, you are going to expose a REST API for your My Documents Spring application so that other
developers can add documents to your application.
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