用MQTTfx连接阿里云物联网平台，怎么一直MQTTException

我按官网格式配的设置，怎么就一直出MQTTException。 后面的用户名和密码也设置好了

2019-07-17 15:01:21,271  INFO --- BrokerConnectorController      : onConnect
2019-07-17 15:01:21,272  INFO --- ScriptsController              : Clear console.
2019-07-17 15:01:21,276  INFO --- MqttFX ClientModel             : MqttClient with ID 5CD6367ZYS|securemode=3,signmethod=hmacsha1,timestamp=10| assigned.
2019-07-17 15:01:21,294 ERROR --- MqttFX ClientModel             : Error when connecting
org.eclipse.paho.client.mqttv3.MqttException: MqttException
    at org.eclipse.paho.client.mqttv3.internal.ExceptionHelper.createMqttException(ExceptionHelper.java:38) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    at org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:715) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:?]
    at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:?]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source) ~[?:?]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) ~[?:?]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:?]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:?]
    at java.lang.Thread.run(Unknown Source) [?:?]
Caused by: java.lang.IllegalArgumentException: hostname can't be null
    at java.net.InetSocketAddress.checkHost(Unknown Source) ~[?:?]
    at java.net.InetSocketAddress.<init>(Unknown Source) ~[?:?]
    at org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:76) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    at org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:701) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    ... 7 more
2019-07-17 15:01:21,295 ERROR --- MqttFX ClientModel             : Please verify your Settings (e.g. Broker Address, Broker Port & Client ID) and the user credentials!
org.eclipse.paho.client.mqttv3.MqttException: MqttException
    at org.eclipse.paho.client.mqttv3.internal.ExceptionHelper.createMqttException(ExceptionHelper.java:38) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    at org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:715) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:?]
    at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:?]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source) ~[?:?]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) ~[?:?]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:?]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:?]
    at java.lang.Thread.run(Unknown Source) [?:?]
Caused by: java.lang.IllegalArgumentException: hostname can't be null
    at java.net.InetSocketAddress.checkHost(Unknown Source) ~[?:?]
    at java.net.InetSocketAddress.<init>(Unknown Source) ~[?:?]
    at org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:76) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    at org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:701) ~[org.eclipse.paho.client.mqttv3-1.2.0.jar:?]
    ... 7 more
2019-07-17 15:01:21,301  INFO --- ScriptsController              : Clear console.
2019-07-17 15:01:21,302 ERROR --- BrokerConnectService           : MqttException

遇到了同样的问题，在CSDN看到了，希望阿里云团队能够给出正确、标准的答案~请查看