PROSAGA码农传奇-MQTT/MODBUS-MQTT PAHO - 用于确认成功传递消息的MessageId

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    不要使用Paho库生成的消息的MQTT id - 因为它
  
  <OL>
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      交付太晚，无法满足您的需求
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      如果您发送大量邮件，可能会重复。
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    相反，使用您自己的ID（甚至可能由您的数据库自动生成）并将其作为用户定义传递
    
      上下文对象
    
     什么时候
    <a href =“https://www.eclipse.org/paho/files/javadoc/org/eclipse/paho/client/mqttv3/IMqttAsyncClient.html#publish-java.lang.String-org.eclipse.paho.client .mqttv3.MqttMessage-java.lang.Object-org.eclipse.paho.client.mqttv3.IMqttActionListener-“rel =”nofollow noreferrer“>
      出版
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    ：
  
   <pre>
 <code>
 Long databaseId = 42;
ObjectMapper objectMapper = new ObjectMapper();
MqttMessage mqttMessage = new MqttMessage();
mqttMessage.setPayload(objectMapper.writeValueAsString(myObject).getBytes()); 
mqttMessage.setQos(1);
this.client.publish("/myTopic", mqttMessage, databaseId, mPublishCallback);

</code>
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    稍后您可以在发布回调方法中检索id：
  
   <pre>
 <code>
 private final IMqttActionListener mPublishCallback = new IMqttActionListener() {
 @Override
 public void onSuccess(IMqttToken publishToken) {
 Long databaseId = (Long) publishToken.getUserContext();
 }

@Override
    public void onFailure(IMqttToken publishToken, Throwable ex) {
        Long databaseId = (Long) publishToken.getUserContext();
    }
};

</code>
 </pre>
  
    另外，您使用的是同步客户端吗？我更喜欢使用
    <a href =“https://www.eclipse.org/paho/files/javadoc/org/eclipse/paho/client/mqttv3/IMqttAsyncClient.html#publish-java.lang.String-org.eclipse.paho.client .mqttv3.MqttMessage-java.lang.Object-org.eclipse.paho.client.mqttv3.IMqttActionListener-“rel =”nofollow noreferrer“>
      IMqttAsyncClient
    </A>
  
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