Question

我需要通过一个主题将命令发送到AWS IoT设备，并且该设备在另一个主题上发布该命令的结果。这遵循AWS IoT的常规异步发布子模型。

我正在尝试为此创建一个请求答复API，并且已经能够通过以下代码实现：注意：使用同一主题发布和订阅模拟设备行为以进行测试。

问题是： 有没有一种方法可以摆脱Thread.sleep并使用某种future.get，它会等到对象不为null并从设备或超时中将某些值作为“ onMessage”的一部分返回，以先发生的为准。

BlockingPubSubIot.java
// This waits for the data to be received on the same topic as published to mimic the device behavior (for testing), and block the function to retrieve the result in a blocking way

    public static void main(String args[]) throws InterruptedException, AWSIotException, AWSIotTimeoutException {
        CommandArguments arguments = CommandArguments.parse(args);
        initClient(arguments);

        System.out.println("Connectionto IoT");
        awsIotClient.connect();

        String returnData = null;
        NonBlockingListener listener = 
            new NonBlockingListener(TestTopic, TestTopicQos, returnData);

        AWSIotTopic topic = listener;
        System.out.println("Subscribing first");
        awsIotClient.subscribe(topic, false);

        String payload = "hello  world";

        System.out.println("Publishing payload to IoT now");
        awsIotClient.publish(TestTopic, payload);

        System.out.println("Waiting for the data via non blocking listener variable");
        String data = listener.getReturnData();

        /**
         * 
         * Can we make this better or this is the right thing to do here
         * like wait using some kind of future where I can just do get
         * and it blocks till the value is not null before a given timeout
         * 
         */
        for(int i =0;i<3 && data == null; i++) {
            Thread.sleep(100);
            System.out.println("Try " + i);
            data = listener.getReturnData();
        }

        if(null == data) {// if its still null
            // Do some exception handling
        }

        //Success
        System.out.println("Data after subscribing synchronously is " + data);

        //Disconnect at the end
        awsIotClient.disconnect();
    }

NonBlockingListener that sets the returnData variable on receiving the message from Iot

public class NonBlockingListener extends AWSIotTopic {

    private String returnData;
    public NonBlockingListener(String topic, AWSIotQos qos, String returnData) {
        super(topic, qos);
        this.returnData = returnData;
        System.out.println("Initializing Callable");
    }

    public String getReturnData() {
        return returnData;
    }

    @Override
    public void onMessage(AWSIotMessage message) {
        returnData = message.getStringPayload();
        //System.out.println(System.currentTimeMillis() + ": <<< " + message.getStringPayload());
        System.out.println("Data is "+ returnData);
    }

}

要求IoT异步答复回复发布订阅

0 个答案: