ApsaraMQ for RocketMQ:Send and receive normal messages

Prerequisites

Before you start, make sure that the following operations are performed:

• Install the SDK for Java. For more information, see Prepare the environment.

• Create the resources that you want to specify in the code in the ApsaraMQ for RocketMQ console. The resources include instances, topics, and consumer groups. For more information, see Create resources.

• Obtain the AccessKey pair of your Alibaba Cloud account. For more information, see Create an AccessKey pair.

Send normal messages

The following sample code provides an example on how to send normal messages by using the HTTP client SDK for Java:

import com.aliyun.mq.http.MQClient;
import com.aliyun.mq.http.MQProducer;
import com.aliyun.mq.http.model.TopicMessage;

import java.util.Date;

public class Producer {

    public static void main(String[] args) {
        MQClient mqClient = new MQClient(
                // The HTTP endpoint. You can obtain the endpoint in the HTTP Endpoint section of the Instance Details page in the ApsaraMQ for RocketMQ console. 
                "${HTTP_ENDPOINT}",
                // Make sure that the environment variables ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are configured. 
                // The AccessKey ID that is used for authentication. 
	              System.getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"),
	              // The AccessKey secret that is used for authentication. 
	              System.getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET")
        );

        // The topic in which the message is produced. You must create the topic in the ApsaraMQ for RocketMQ console. 
        // Each topic can be used to send and receive messages of a specific type. For example, a topic that is used to send and consume normal messages cannot be used to send or receive messages of other types. 
        final String topic = "${TOPIC}";
        // The ID of the instance to which the topic belongs. You must create the instance in the ApsaraMQ for RocketMQ console. 
        // If the instance has a namespace, specify the ID of the instance. If the instance does not have a namespace, set the instanceID parameter to null or an empty string. You can obtain the namespace of the instance on the Instance Details page in the ApsaraMQ for RocketMQ console. 
        final String instanceId = "${INSTANCE_ID}";

        // Obtain the producer that sends messages to the topic. 
        MQProducer producer;
        if (instanceId != null && instanceId != "") {
            producer = mqClient.getProducer(instanceId, topic);
        } else {
            producer = mqClient.getProducer(topic);
        }

        try {
            // Cyclically send four messages. 
            for (int i = 0; i < 4; i++) {
                TopicMessage pubMsg;        // The normal message. 
                pubMsg = new TopicMessage(
                // The message content. 
                "hello mq!".getBytes(),
                // The message tag. 
                "A"
                );
                // The custom attributes of the message. 
                pubMsg.getProperties().put("a", String.valueOf(i));
                // The message key. 
                pubMsg.setMessageKey("MessageKey");
               
            // Send the message in synchronous transmission mode. If no exception is thrown, the message is sent. 
            TopicMessage pubResultMsg = producer.publishMessage(pubMsg);

            // Send the message in synchronous transmission mode. If no exception is thrown, the message is sent. 
            System.out.println(new Date() + " Send mq message success. Topic is:" + topic + ", msgId is: " + pubResultMsg.getMessageId()
                        + ", bodyMD5 is: " + pubResultMsg.getMessageBodyMD5());
            }
        } catch (Throwable e) {
            // The logic that you want to use to resend or persist the message if the message fails to be sent and needs to be sent again. 
            System.out.println(new Date() + " Send mq message failed. Topic is:" + topic);
            e.printStackTrace();
        }

        mqClient.close();
    }

}

Subscribe to normal messages

The following sample code provides an example on how to subscribe to normal messages by using the HTTP client SDK for Java:

import com.aliyun.mq.http.MQClient;
import com.aliyun.mq.http.MQConsumer;
import com.aliyun.mq.http.common.AckMessageException;
import com.aliyun.mq.http.model.Message;

import java.util.ArrayList;
import java.util.List;

public class Consumer {

    public static void main(String[] args) {
        MQClient mqClient = new MQClient(
                // The HTTP endpoint. You can obtain the endpoint in the HTTP Endpoint section of the Instance Details page in the ApsaraMQ for RocketMQ console. 
                "${HTTP_ENDPOINT}",
                // Make sure that the environment variables ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are configured. 
                // The AccessKey ID that is used for authentication. 
	              System.getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"),
	              // The AccessKey secret that is used for authentication. 
	              System.getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET")
        );

        // The topic in which the message is produced. You must create the topic in the ApsaraMQ for RocketMQ console. 
        // Each topic can be used to send and receive messages of a specific type. For example, a topic that is used to send and receive normal messages cannot be used to send or receive messages of other types. 
        final String topic = "${TOPIC}";
        // The ID of the consumer group that you created in the ApsaraMQ for RocketMQ console. 
        final String groupId = "${GROUP_ID}";
        // The ID of the instance to which the topic belongs. You must create the instance in the ApsaraMQ for RocketMQ console. 
        // If the instance has a namespace, specify the ID of the instance. If the instance does not have a namespace, set the instanceID parameter to null or an empty string. You can obtain the namespace of the instance on the Instance Details page in the ApsaraMQ for RocketMQ console. 
        final String instanceId = "${INSTANCE_ID}";

        final MQConsumer consumer;
        if (instanceId != null && instanceId != "") {
            consumer = mqClient.getConsumer(instanceId, topic, groupId, null);
        } else {
            consumer = mqClient.getConsumer(topic, groupId);
        }

        // Cyclically consume messages in the current thread. We recommend that you use multiple threads to concurrently consume messages. 
        do {
            List<Message> messages = null;

            try {
                // Consume messages in long polling mode. 
                // In long polling mode, if no message in the topic is available for consumption, the request is suspended on the broker for the specified period of time. If a message becomes available for consumption within the specified period of time, the broker immediately sends a response to the consumer. In this example, the value is specified as 3 seconds. 
                messages = consumer.consumeMessage(
                        3,// Specify the maximum number of messages that can be consumed at a time. In this example, the value is specified as 3. The maximum value that you can specify is 16. 
                        3// The duration of a long polling cycle. Unit: seconds. In this example, the value is specified as 3. The maximum value you can specify is 30. 
                );
            } catch (Throwable e) {
                e.printStackTrace();
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
            }
            // No message in the topic is available for consumption. 
            if (messages == null || messages.isEmpty()) {
                System.out.println(Thread.currentThread().getName() + ": no new message, continue!");
                continue;
            }

            // The message consumption logic. 
            for (Message message : messages) {
                System.out.println("Receive message: " + message);
            }

            // If the broker does not receive an acknowledgment (ACK) for a message from the consumer before the delivery retry interval elapses, the broker sends the message for consumption again. 
            // A unique timestamp is specified for the handle of a message each time the message is consumed. 
            {
                List<String> handles = new ArrayList<String>();
                for (Message message : messages) {
                    handles.add(message.getReceiptHandle());
                }

                try {
                    consumer.ackMessage(handles);
                } catch (Throwable e) {
                    // If the handle of a message times out, the broker cannot receive an ACK for the message from the consumer. 
                    if (e instanceof AckMessageException) {
                        AckMessageException errors = (AckMessageException) e;
                        System.out.println("Ack message fail, requestId is:" + errors.getRequestId() + ", fail handles:");
                        if (errors.getErrorMessages() != null) {
                            for (String errorHandle :errors.getErrorMessages().keySet()) {
                                System.out.println("Handle:" + errorHandle + ", ErrorCode:" + errors.getErrorMessages().get(errorHandle).getErrorCode()
                                        + ", ErrorMsg:" + errors.getErrorMessages().get(errorHandle).getErrorMessage());
                            }
                        }
                        continue;
                    }
                    e.printStackTrace();
                }
            }
        } while (true);
    }
}