Question

在我的代码中，有四个类：mainProgram，Coordinator类，Client Class和Callback Class。 mainProgram包含程序的主要方法，它创建一个Coordinator类的实例并调用它的start（）方法。后者创建客户端类的两个实例，发布者和订阅者，连接它们并将其中一个实例（订阅者）订阅到多个主题。客户端类包含与mqtt有关的所有内容以及有关subscribe方法的Callback，我为此创建了一个自己的类，Callback Class在messageArrived方法中接收传入的mqtt消息。

这是主要代码：

public class mainProgram throws MqttException {

public static void main(String[] args) {
    Coordinator coordinator=new Coordinator();
    coordinator.start();
}}

这是Coordinator类的代码：

public class Coordinator  { 
      Client publisher;
      Client subscriber;

      public Coordinator() {
         // TODO Auto-generated constructor stub
      }

      public void start() throws MqttException {
             Client publisher=new Client("publisher","tcp://192.168.0.10",0);
             publisher.connect();
             Client subscriber=new Client("subscriber","tcp://192.168.0.10",0);
             subscriber.connect();
             subscriber.subscribeToTopic(new String [] {"home/Sensor2","home/Sensor3"});    
      }

      public void getMessage(String message) throws MqttPersistenceException, MqttException {
            publisher.publish("home/Sensor4", message); 
      }}

这是客户类：

public class Client  {
      String brokerAddress;
      String clientId;
      int qos;
      MqttClient mqttClient;
      MqttConnectOptions conOpt;
      MemoryPersistence persistence;
      Coordinator coordinator;

      public Client(String clientId, String brokerAddress, int qos) {   
            this.clientId=clientId;
            this.brokerAddress=brokerAddress;
            this.qos=qos;
            this.setConOpt();
      }

      public void setConOpt() { 
           conOpt=new MqttConnectOptions();
           conOpt.setKeepAliveInterval(30);                         
           conOpt.setAutomaticReconnect(false);                         
      }

      public void connect() throws MqttException {

        mqttClient=new MqttClient(brokerAddress,clientId,persistence);
        this.mqttClient.setCallback(new Callback(this));                    

        this.mqttClient.connect(this.conOpt);

        while(this.mqttClient.isConnected()==false) {
            System.out.println("Connecting");
            System.out.println("...");
        }

        if(this.mqttClient.isConnected()==true){
            System.out.println("Der Mqttclient "+this.mqttClient.getClientId()+" is now connected!");   
        }
     }

     public void subscribeToTopic(String [] topics) throws MqttException {
              for(int i=0;i<topics.length;i++) {
                     this.mqttClient.subscribe(topics[i]);
              } 
    }

    public void publish(String topic, String message) throws MqttPersistenceException, MqttException {      
            MqttMessage mqttMessage=new MqttMessage(message.getBytes());
            this.mqttClient.publish(topic, mqttMessage);
    }
}

这是回调类：

public class Callback implements MqttCallback{

Client client;

public Callback(Client client)  {
    // TODO Auto-generated constructor stub
    this.client=client;
}

@Override
public void connectionLost(Throwable arg0) {
    // TODO Auto-generated method stub
    System.out.println("Connection to server's lost");
}

@Override
public void deliveryComplete(IMqttDeliveryToken arg0) {
    // TODO Auto-generated method stub
    System.out.println("Message's delivered");
}

@Override
public void messageArrived(String topic, MqttMessage message) throws Exception {
        String ingoingMsg=message.toString();
        System.out.println("until here all's fine");
        Coordinator coordinator=new Coordinator();
        coordinator.getMessage(ingoingMsg);
}
}

程序启动，创建客户端，当我通过MQTTfx向上述提及的主题发布消息时，在控制台中显示：

当我调用方法“coordinator.getMessage（）”并且没有发布任何内容时，程序结束并且客户端“subscriber”的连接结束。

最后，程序应该像这样：

创建客户
连接客户
订阅订阅者客户端
收听并发布订阅主题的消息：调用协调器类的getMessage以发布内容
发布时，在发布之后，监听其他消息不应该结束，并且程序“在循环中”，直到用户将其分解为止。

我到处寻找解决方案，但我在网上遇到的问题并不完全相同。也许你有一些有启发性的提示......

Java Mqtt Client在回调收到一条消息后断开连接

0 个答案: