Dispose mqtt client on application close

src/main/kotlin/de/smartsquare/starter/mqtt/DisposableMqtt3Client.kt

@@ -0,0 +1,12 @@
+package de.smartsquare.starter.mqtt
+
+import com.hivemq.client.mqtt.mqtt3.Mqtt3Client
+import org.springframework.beans.factory.DisposableBean
+import java.util.concurrent.TimeUnit
+
+class DisposableMqtt3Client(private val delegate: Mqtt3Client) : Mqtt3Client by delegate, DisposableBean {
+
+    override fun destroy() {
+        delegate.toAsync().disconnect().get(10, TimeUnit.SECONDS)
+    }
+}

src/main/kotlin/de/smartsquare/starter/mqtt/MqttAutoConfiguration.kt

@@ -58,7 +58,7 @@ class MqttAutoConfiguration {
             } else {
                 logger.info("Successfully connected to broker.")
 
-                return client
+                return DisposableMqtt3Client(client)
             }
         } catch (e: TimeoutException) {
             throw BrokerConnectException("Broker ${config.host}:${config.port} did not respond within 10 seconds.", e)