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Synchronous Subscriptions
Synchronous subscriptions require the application to wait for messages. This type of subscription is easy to set-up and use, but requires the application to deal with looping if multiple messages are expected. For situations where a single message is expected, synchronous subscriptions are sometimes easier to manage, depending on the language.
For example, to subscribe to the subject updates and receive a single message you could do:
nc, err := nats.Connect("demo.nats.io")
if err != nil {
log.Fatal(err)
}
defer nc.Close()
// Subscribe
sub, err := nc.SubscribeSync("updates")
if err != nil {
log.Fatal(err)
}
// Wait for a message
msg, err := sub.NextMsg(10 * time.Second)
if err != nil {
log.Fatal(err)
}
// Use the response
log.Printf("Reply: %s", msg.Data)
Connection nc = Nats.connect("nats://demo.nats.io:4222");
// Subscribe
Subscription sub = nc.subscribe("updates");
// Read a message
Message msg = sub.nextMessage(Duration.ZERO);
String str = new String(msg.getData(), StandardCharsets.UTF_8);
System.out.println(str);
// Close the connection
nc.close();