Java Eclipse Paho实现 - 自动重新连接 [英] Java Eclipse Paho Implementation - Auto reconnect

问题描述

我正在尝试在我的项目中实现 eclipse.paho ，以连接Mqtt Broker（订阅和发布目的）。问题是，当我使用订阅功能（实现 MqttCallback 接口）时，我无法确定如果连接丢失，我该如何重新连接。 MqttCallback接口具有connectionLost方法，但是对于调试造成连接丢失的原因很有用。我搜索，但找不到建立自动重新连接的方法。你能建议一个关于这个问题的方式或文件吗？

感谢高级。

解决方案

是构建你的连接逻辑，所以它生活在一个自己的方法，所以它可以再次从 connectionLost 回调在 MqttCallback 实例。

connectionLost 方法传递一个Throwable，这将是触发断开连接的异常因此，您可以根据原因做出决定，以及如何重新连接/如何重新连接。

连接方法应该连接并订阅所需的主题。 p>

如下所示：

  public class PubSub {
 
 MqttClient客户端; 
字符串主题[] = [foo /＃，bar]; 
 MqttCallback callback = new MqttCallback（）{
 public void connectionLost（Throwable t）{
 this.connect（）; 
} 
 
 public void messageArrived（String topic，MqttMessage message）throws异常{
 System.out.println（topic  - + topic +：+ new String message.getPayload（）））; 
} 
 
 public void deliveryComplete（IMqttDeliveryToken token）{
} 
}; 
 
 public static void main（String args []）{
 PubSub foo = new PubSub（）; 
} 
 
 public PubSub（）{
 this.connect（）; 
} 
 
 public void connect（）{
 client = new MqttClient（mqtt：// localhost，pubsub-1）; 
 client.setCallback（callback）; 
 client.connect（）; 
 client.subscribe（topics）; 
} 
 
} 
  

I'm trying to implement eclipse.paho in my project to connect Mqtt Broker (Both subscribing and publishing purpose). The problem is, when I using the subscribing feature (Implementing MqttCallback interface), I couldn't figure our how can I reconnect if the connection lost. MqttCallback interface has a connectionLost method, but it is useful for the debug what causes the connection lost. I searched but couldn't find a way to establish auto reconnect. Can you suggest a way or document about this problem?

Thanks in advanced.

解决方案

The best way to do this is to structure your connection logic so it lives in a method on it's own so it can be called again from the connectionLost callback in the MqttCallback instance.

The connectionLost method is passed a Throwable that will be the exception that triggered the disconnect so you can make decisions about the root cause and how this may effect when/how you reconnect.

The connection method should connect and subscribe to the topics you require.

Something like this:

public class PubSub {

  MqttClient client;
  String topics[] = ["foo/#", "bar"];
  MqttCallback callback = new MqttCallback() {
    public void connectionLost(Throwable t) {
      this.connect();
    }

    public void messageArrived(String topic, MqttMessage message) throws Exception {
      System.out.println("topic - " + topic + ": " + new String(message.getPayload()));
    }

    public void deliveryComplete(IMqttDeliveryToken token) {
    }
  };

  public static void main(String args[]) {
    PubSub foo = new PubSub();
  }

  public PubSub(){
    this.connect();
  }

  public void connect(){
    client = new MqttClient("mqtt://localhost", "pubsub-1");
    client.setCallback(callback);
    client.connect();
    client.subscribe(topics);
  }

}

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