Question

我正在尝试将Java ME App Client连接到MQTT代理。我能够创建一个客户端，交叉检查客户端服务器URI 但是当我尝试连接时，我看到异常：

以下是代码：

try {
    myClient = new MqttClient(BROKER_URL, MqttClient.generateClientId()); //, new MemoryPersistence());

                if(myClient == null)
                {
                    System.out.println("myClient = NULL");
                    return;
                }
                System.out.println("ServerURI: "+myClient.getServerURI());
               System.out.println("is Connected: "+myClient.isConnected());


                 System.out.println("Setting Call back");
    myClient.setCallback(new MqttCallback() {

                    @Override
                    public void connectionLost(Throwable cause) {
                        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
                    }

                    @Override
                    public void messageArrived(String topic, MqttMessage message) throws Exception {
                         // String payload = new String(message.getPayload());
                        System.out.println(topic+ "--->"+ new String(message.getPayload()));
                        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.

                    }

                    @Override
                    public void deliveryComplete(IMqttDeliveryToken token) {
                        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
                    }
                });


                 System.out.println("Trying to Connect to BROKER");
    myClient.connect(); 
                //  myClient.connect(connOpt);
                System.out.println("Subscribing to WORLD TOPIC");
                myClient.subscribe("world");
} catch (MqttException e) {

            System.out.println("--- Caught Exception ---");
           // System.out.println("Exception: "+e.toString());
    e.printStackTrace();
    System.exit(-1);
            return;
}

我在连接上得到并且异常。这是例外：

 java.lang.NullPointerException
 - org/eclipse/paho/client/mqttv3/internal/MessageCatalog.getMessage(MessageCatalog.java:46)
 - org/eclipse/paho/client/mqttv3/MqttException.getMessage(MqttException.java:200)
 - org/eclipse/paho/client/mqttv3/MqttException.toString(MqttException.java:208)
 - java/lang/String.valueOf(), bci=11
 - java/io/PrintStream.print(), bci=2
 - java/io/PrintStream.println(), bci=2
 - java/lang/Throwable.printStackTrace(), bci=2
 - java/lang/Throwable.printStackTrace(), bci=4
 - javameapp82/SimpleMqttClient.testMQTTClient(SimpleMqttClient.java:96)
 - javameapp82/JavaMEApp82.startApp(JavaMEApp82.java:50)
 - javax/microedition/midlet/MIDletTunnelImpl.callStartApp(), bci=1
 - com/sun/midp/midlet/MIDletPeer.startApp(), bci=5
 - com/sun/midp/midlet/MIDletStateHandler.startSuite(), bci=264
 - com/sun/midp/main/AbstractMIDletSuiteLoader.startSuite(), bci=38
 - com/sun/midp/main/CldcMIDletSuiteLoader.startSuite(), bci=5
 - com/sun/midp/main/AbstractMIDletSuiteLoader.runMIDletSuite(), bci=132
 - com/sun/midp/main/AppIsolateMIDletSuiteLoader.main(), bci=26

不知道为什么我会得到这个例外，谢谢你的帮助。

Java ME上MQTT客户端连接的例外情况

0 个答案: