🔸 TLDR
▪️ Queue = 1 message → 1 consumer (work distribution) ✅
▪️ Topic = 1 message → N subscribers (broadcast) 📣
▪️ Durable subscription = don’t miss messages while offline 🧷
🔸 CONTEXT (WHAT JMS IS, WITHOUT THE HYPE)
▪️ JMS is a Java API for messaging (asynchronous communication) between apps 📨
▪️ It’s about exchanging messages through a broker (ex: ActiveMQ, Artemis, IBM MQ…)
🧩 ▪️ Two main models: Queue (point-to-point) vs Topic (pub/sub) 🔀
🔸 MESSAGE QUEUES (POINT-TO-POINT) 📬
▪️ Producer sends to a queue
▪️ Consumers compete: each message is handled by only one consumer
▪️ Great for: background jobs, email sending, payments processing, retries ⚙️
Send a message to a queue
Queue queue = session.createQueue("orders.queue"); MessageProducer producer = session.createProducer(queue); TextMessage msg = session.createTextMessage("orderId=42"); producer.send(msg);
Receive a message from a queue
Queue queue = session.createQueue("orders.queue"); MessageConsumer consumer = session.createConsumer(queue); // blocking receive (demo purpose) Message message = consumer.receive(5000); if (message instanceof TextMessage tm) { System.out.println("Received: " + tm.getText()); } Browse a queue (peek without consuming) 👀 Queue queue = session.createQueue("orders.queue"); QueueBrowser browser = session.createBrowser(queue); var enumeration = browser.getEnumeration(); while (enumeration.hasMoreElements()) { Message m = (Message) enumeration.nextElement(); System.out.println("Peek message: " + m.getJMSMessageID()); }
🔸 MESSAGE TOPICS (PUBLISH / SUBSCRIBE) 📣
▪️ Producer publishes to a topic
▪️ Every subscriber gets a copy (fan-out) 🌪️
▪️ Great for: domain events, notifications, cache invalidation, audit streams 🧠
Publish to a topic
Topic topic = session.createTopic("events.topic"); MessageProducer producer = session.createProducer(topic); producer.send(session.createTextMessage("user.signed_up id=99"));
Subscribe to a topic
Topic topic = session.createTopic("events.topic"); MessageConsumer subscriber = session.createConsumer(topic); Message msg = subscriber.receive(5000); System.out.println(((TextMessage) msg).getText()); Create a durable subscriber (don’t miss events while disconnected) 🧷 connection.setClientID("billing-service"); // required for durable sub Topic topic = session.createTopic("events.topic"); MessageConsumer durable = session.createDurableSubscriber(topic, "billing-subscription"); Message msg = durable.receive(5000); System.out.println(((TextMessage) msg).getText());
🔸 TAKEAWAYS ✅
▪️ Use Queue when you want work to be processed once (load-balanced consumers) ⚖️
▪️ Use Topic when you want broadcast (many services react to the same event) 📡
▪️ Use Durable Subscribers when subscribers must not miss messages (even offline) 🧱
▪️ JMS is an API: behavior depends on your broker + config (delivery mode, ack, redelivery…) 🔧
🔸 QUESTION FOR YOU 🤔
▪️ In your projects: are you mostly Queue-first or Topic-first?
#Java #JMS #Messaging #EventDrivenArchitecture #Integration #Microservices #Backend #Architecture #JavaDevelopers #AsyncProcessing
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