Java Messaging Service API

Let's look at how Reactive Streams compares to the Java Messaging Service (JMS) API. The JMS specification describes a Queue and a Topic, to which a producer and a consumer can connect:

@Resource(lookup = "jms/Queue")
private static Queue queue;

@Resource(lookup = "jms/Topic")
private static Topic topic;
Session session = connection.createSession(false,Session.AUTO_ACKNOWLEDGE);
MessageProducer producer = session.createProducer(queue);
MessageConsumer consumer = session.createConsumer(topic)

Here, the producer  is responsible for generating unbounded events on the queue or topics, while the consumer actively consumes the events. The producer and consumer are working in isolation, at their own rates. The task of managing the subscription is taken care of by the JMS broker. This is different from the Subscription API, where backpressure plays a major role in event generation. There is also no event modeling, like subscription, error, or completion. The JMS connection is like a never-ending stream of data. It cannot provide completion or error events. If we need to support this, custom objects must be modeled first.