Evaluation - Autonomics Development: A Domain-Specific Aspect Language Approach - page 98

public class Publisher {
public static void main(String[] args) {
Publisher a = new Publisher();
a.publish( "This is a test String \ldots{}" );
System.exit(0);

}

public void publish(String s) {
}

}

Figure 6.2. Java Publisher class.

public class Subscriber {
public static void main(String[] args) throws InterruptedException {
Subscriber a = new Subscriber();
while (true){
a.subscribe( "This is not from the producer" );
Thread.sleep(5000);

}

}

public void subscribe(String message) {
System.out.println( "Received: " + message);

}

}

Figure 6.3. Java Subscriber class.

The Publisher class is altered so that calls to its publish() method are
altered to send the String parameter as a message on the REMOTEJ.SEND topic.
As can be seen in Figure 6.2 and Figure 6.3, the existing code is unaware of the
protocol or recovery scenario that will be applied to it.
Running the applications verifies that the test applications work as expected
with the Publisher.publish() method sending String objects that are received
by the Subscriber.subscribe() method asynchronously.

6.2.4 Summary

In this section we have evaluated the extendibility of the RemoteJ system by
adding two additional protocols, pub and sub . In contrast to the RMI, REST and
JMS protocols, the sub protocol is event-driven as it alters the matched method
to receive data asynchronously. The pub protocol alters the matched method to
send its parameter as a message on a topic.
Both protocols are asynchronous and loosely-coupled in nature and are there-
fore decoupled in time , space and synchronisation , and our evaluation has demon-