BAEL-1545 - Nats Tutorial (#3904)

2018-03-29 01:06:24 -04:00
parent 5b00f0e0e3
commit 48b8d2c8a5
3 changed files with 273 additions and 0 deletions
@@ -0,0 +1,150 @@
+package com.baeldung.jnats;
+
+import io.nats.client.*;
+
+import java.io.IOException;
+import java.util.*;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class NatsClient {
+
+    private String serverURI;
+
+    private Connection natsConnection;
+
+    private Map<String, Subscription> subscriptions = new HashMap<>();
+
+    private final static Logger log = LoggerFactory.getLogger(NatsClient.class);
+
+    public NatsClient() {
+        this.serverURI = "jnats://localhost:4222";
+        natsConnection = initConnection(serverURI);
+    }
+
+
+    public NatsClient(String serverURI) {
+
+        if ((serverURI != null) && (!serverURI.isEmpty())) {
+            this.serverURI = serverURI;
+        } else {
+            this.serverURI = "jnats://localhost:4222";
+        }
+
+        natsConnection = initConnection(serverURI);
+    }
+
+    public void closeConnection() {
+        // Close connection
+        natsConnection.close();
+    }
+
+
+    private Connection initConnection(String uri) {
+        try {
+
+            Options options = new Options.Builder()
+              .errorCb(new ExceptionHandler() {
+                  @Override
+                  public void onException(NATSException ex) {
+                      log.error("Connection Exception: ", ex);
+                  }
+              })
+              .disconnectedCb(new DisconnectedCallback() {
+                  @Override
+                  public void onDisconnect(ConnectionEvent event) {
+                      log.error("Channel disconnected: {}", event.getConnection());
+                  }
+              })
+              .reconnectedCb(new ReconnectedCallback() {
+                  @Override
+                  public void onReconnect(ConnectionEvent event) {
+                      log.error("Reconnected to server: {}", event.getConnection());
+                  }
+              })
+              .build();
+
+            return Nats.connect(uri, options);
+
+        } catch (IOException ioe) {
+            log.error("Error connecting to NATs! ", ioe);
+            return null;
+        }
+    }
+
+
+    public void publishMessage(String topic, String replyTo, String message) {
+        try {
+            // Simple Publisher
+            natsConnection.publish(topic, replyTo, message.getBytes());
+        } catch (IOException ioe) {
+            log.error("Error publishing message: {} to {} ", message, topic, ioe);
+        }
+    }
+
+
+    public void subscribeAsync(String topic) {
+
+        // Simple Async Subscriber
+        AsyncSubscription subscription = natsConnection.subscribe(topic, new MessageHandler() {
+            @Override
+            public void onMessage(Message msg) {
+                log.info("Received message on {}", msg.getSubject());
+            }
+        });
+
+        if (subscription == null) {
+            log.error("Error subscribing to {}", topic);
+        } else {
+            subscriptions.put(topic, subscription);
+        }
+    }
+
+    public SyncSubscription subscribeSync(String topic) {
+        // Simple Sync Subscriber
+        return natsConnection.subscribe(topic);
+    }
+
+    public void unsubscribe(String topic) {
+
+        try {
+            Subscription subscription = subscriptions.get(topic);
+
+            if (subscription != null) {
+                subscription.unsubscribe();
+            } else {
+                log.error("{} not found. Unable to unsubscribe.", topic);
+            }
+
+        } catch (IOException ioe) {
+            log.error("Error unsubscribing from {} ", topic, ioe);
+        }
+    }
+
+
+    public Message makeRequest(String topic, String request) {
+
+        try {
+            return natsConnection.request(topic, request.getBytes(), 100);
+        } catch (IOException | InterruptedException ioe) {
+            log.error("Error making request {} to {} ", topic, request, ioe);
+            return null;
+        }
+    }
+
+    public void installReply(String topic, String reply) {
+        natsConnection.subscribe(topic, message -> {
+            try {
+                natsConnection.publish(message.getReplyTo(), reply.getBytes());
+            } catch (Exception e) {
+                e.printStackTrace();
+            }
+        });
+    }
+
+    public SyncSubscription joinQueueGroup(String topic, String queue) {
+        return natsConnection.subscribe(topic, queue);
+    }
+
+}