ApsaraMQ for RocketMQ:Send and subscribe to delayed messages

import com.aliyun.openservices.ons.api.Message;
import com.aliyun.openservices.ons.api.ONSFactory;
import com.aliyun.openservices.ons.api.Producer;
import com.aliyun.openservices.ons.api.PropertyKeyConst;
import com.aliyun.openservices.ons.api.SendResult;
import java.util.Date;
import java.util.Properties;

public class ProducerDelayTest {
    public static void main(String[] args) {
        Properties properties = new Properties();
        // Retrieve the AccessKey pair from environment variables.
        // Make sure ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are set.
        properties.put(PropertyKeyConst.AccessKey, System.getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"));
        properties.put(PropertyKeyConst.SecretKey, System.getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET"));

        // Specify the TCP endpoint.
        // Find this value in the TCP Endpoint section of the Instance Details page
        // in the ApsaraMQ for RocketMQ console.
        properties.put(PropertyKeyConst.NAMESRV_ADDR, "<your-tcp-endpoint>");

        Producer producer = ONSFactory.createProducer(properties);
        // Call start() once before sending any messages.
        producer.start();

        Message msg = new Message(
                "<your-topic>",       // Topic created in the console
                "DelayMessageTag",    // Tag for consumer-side filtering, similar to a Gmail tag
                "Hello MQ".getBytes() // Message body in binary format.
                                      // ApsaraMQ for RocketMQ does not process message bodies.
                                      // Producer and consumer must agree on serialization.
        );
        // Optional: set a business key for message tracing.
        // The key should be globally unique when possible. Use it to query
        // or resend messages in the ApsaraMQ for RocketMQ console.
        msg.setKey("ORDERID_100");

        try {
            // Set the delivery time to 3 seconds from now.
            // The value is an absolute timestamp in milliseconds.
            // The maximum delay that you can specify is 40 days.
            long delayTime = System.currentTimeMillis() + 3000;
            msg.setStartDeliverTime(delayTime);

            // Send the message in synchronous transmission mode.
            // If no exception is thrown, the message is sent.
            SendResult sendResult = producer.send(msg);
            if (sendResult != null) {
                System.out.println(new Date() + " Send mq message success. Topic is:"
                        + msg.getTopic() + " msgId is: " + sendResult.getMessageId());
            }
        } catch (Exception e) {
            // Handle send failure: log, retry, or persist the message.
            System.out.println(new Date() + " Send mq message failed. Topic is:" + msg.getTopic());
            e.printStackTrace();
        }

        // Shut down the producer when the application exits.
        // For high-throughput scenarios, keep the producer running and reuse it.
        producer.shutdown();
    }
}