Question

我已经在Java中下载了一个示例，以演示Paho MQTT。

 public class Thermometer {

    public static final String BROKER_URL = "tcp://test.mosquitto.org:1883";

    public static final String TOPIC = "xyz.abc";

    private MqttClient client;


    public Thermometer() {
        try {
            MemoryPersistence per = new MemoryPersistence();
            String clientId = UUID.randomUUID().toString();
            client = new MqttClient(BROKER_URL, clientId, per);
        } catch (MqttException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

运行时出现问题，它位于client = new MqttClient(BROKER_URL, clientId, per);

线程中的异常＆＃34; main＆＃34; java.lang.IllegalArgumentException异常在org.eclipse.paho.client.mqttv3.MqttClient。（MqttClient.java:170）在mqtt_pub.Thermometer。（Thermometer.java:26）在mqtt_pub.Thermometer.main（Thermometer.java:65）

我发现@throws IllegalArgumentException如果QoS的值不是0,1或2但是在类MemoryPersistence中他们没有提到。请帮助，提前谢谢。

Answer 1

如果您查看MttqClient的{{3}}，则可以看到uuid的长度最多只能为23个字符。看起来uuid更长：

if (clientId == null || clientId.length() == 0 || clientId.length() > 23)  
{
      throw new IllegalArgumentException();
}

UUID.randomUUID().toString()返回一个长度为36 char的字符串;

Paho MQTT抛出异常

1 个答案: