Modify some console output as logger print for MqttListener.

src/main/java/com/example/tdl/mqtt/MqttListener.java

@@ -80,18 +80,18 @@ public class MqttListener implements MqttCallback {
                             try {
                                 mqttAsyncClient.subscribe(listener_topic, mqttconfig.getQos());
                             } catch (MqttException e) {
-                                System.out.println("Error: " + e.getMessage());
+                                logger.error("connection MqttException: " + e.getMessage());
                             }
                         }
 
                         @Override
                         public void onFailure(IMqttToken iMqttToken, Throwable throwable) {
-                            System.out.println("connection fail with client id");
+                            logger.error("connection fail with client id");
                         }
                     });
             this.mqttAsyncClient.setCallback(this);
         } catch (Exception e) {
-            e.printStackTrace();
+            logger.error("mqtt initialize exception: " + e.getMessage());
         }
     }