ApsaraMQ for RocketMQ:Transactional messages

import java.time.Duration;
import org.apache.rocketmq.client.apis.*;
import org.apache.rocketmq.client.apis.message.Message;
import org.apache.rocketmq.client.apis.producer.Producer;
import org.apache.rocketmq.client.apis.producer.SendReceipt;
import org.apache.rocketmq.client.apis.producer.Transaction;
import org.apache.rocketmq.client.apis.producer.TransactionResolution;
import org.apache.rocketmq.client.java.message.MessageBuilderImpl;
import org.apache.rocketmq.client.apis.message.MessageBuilder;
import org.apache.rocketmq.shaded.com.google.common.base.Strings;

public class ProducerTransactionMessageExample {
    /**
     // The demo is used to simulate the order table query service to check whether the order transaction is submitted. 
     */
    private static boolean checkOrderById(String orderId) {
        return true;
    }

    /**
     // The demo is used to simulate the execution result of a local transaction. 
     */
    private static boolean doLocalTransaction() {
        return true;
    }

    public static void main(String[] args) throws ClientException {
        /**
         * The endpoint of the instance. You can view the endpoint on the Endpoints tab of the Instance Details page in the ApsaraMQ for RocketMQ console. 
         * If the client of the ApsaraMQ for RocketMQ instance is deployed on an Elastic Compute Service (ECS) instance and you want to access the ApsaraMQ for RocketMQ instance in an internal network, we recommend that you specify the virtual private cloud (VPC) endpoint. 
         * If you access the instance over the Internet or from a data center, you can specify the public endpoint. If you access the instance over the Internet, you must enable the Internet access feature for the instance. 
         */
        String endpoints = "xxx-hangzhou.rmq.aliyuncs.com:8080";
        // The name of the topic to which the message is sent. Before you use a topic to receive a message, you must create the topic in the ApsaraMQ for RocketMQ console. Otherwise, an error is returned. 
        String topic = "topic1";
        ClientServiceProvider provider = ClientServiceProvider.loadService();
        ClientConfigurationBuilder builder = ClientConfiguration.newBuilder().setEndpoints(endpoints);
        /**
         * If you access the instance by using the public endpoint, you must specify the username and password of the instance. You can obtain the username and password on the Intelligent Authentication tab of the Access Control page corresponding to the instance in the ApsaraMQ for RocketMQ console. 
         * If the client of the ApsaraMQ for RocketMQ instance is deployed on an ECS instance and you want to access the ApsaraMQ for RocketMQ instance in an internal network, you do not need to specify the username or password. The broker automatically obtains the username and password based on the VPC information. 
         * If the instance is a serverless instance, you must specify the username and password of the instance, regardless of whether you access the instance over the Internet or in a VPC. 
         */
        builder.setCredentialProvider(new StaticSessionCredentialsProvider("Instance UserName", "Instance Password"));
        builder.setRequestTimeout(Duration.ofMillis(5000));
        ClientConfiguration configuration = builder.build();
        
        MessageBuilder messageBuilder = new MessageBuilderImpl();

        // Build the transaction producer. The producer must build a transaction checker to check the intermediate status of an exceptional half message. 
        Producer producer = provider.newProducerBuilder()
            .setTransactionChecker(messageView -> {
                /**
                 * The transaction checker checks whether the local transaction is correctly committed or rolled back based on the business ID. In this example, an order ID is used. 
                 * If this order is found in the order table, the order insertion action is correctly committed by the local transaction. If no order is found in the order table, the local transaction is rolled back. 
                 */
                final String orderId = messageView.getProperties().get("OrderId");
                if (Strings.isNullOrEmpty(orderId)) {
                    // An error occurs in the message. Rollback is returned. 
                    return TransactionResolution.ROLLBACK;
                }
                return checkOrderById(orderId) ? TransactionResolution.COMMIT : TransactionResolution.ROLLBACK;
            }).setTopics(topic)
            .setClientConfiguration(configuration)
            .build();
        // Create a transaction branch. 
        final Transaction transaction;
        try {
            transaction = producer.beginTransaction();
        } catch (ClientException e) {
            e.printStackTrace();
            // If the transaction branch fails to be created, the transaction is terminated. 
            return;
        }
        Message message = messageBuilder.setTopic(topic)
            // The message key. You can use a keyword to accurately find the message. 
            .setKeys("messageKey1")
            // The message tag. The consumer can use the tag to filter messages. 
            .setTag("messageTag")
            // The unique ID that is associated with the local transaction. The ID is used to verify the query of the local transaction status. 
            .addProperty("OrderId", "xxx")
            // The message body. 
            .setBody("messageBody".getBytes())
            .build();
        // Send the half message.
        final SendReceipt sendReceipt;
        try {
            sendReceipt = producer.send(message, transaction);
        } catch (ClientException e) {
            // If the half message fails to be sent, the transaction is terminated and the message is rolled back. 
            return;
        }
        /**
         * Execute the local transaction and determine the execution result. 
         * 1. If the result is Commit, deliver the message. 
         * 2. If the result is Rollback, roll back the message. 
         * 3. If an unknown exception occurs, no action is performed until a response is obtained from the query of the local transaction status. 
         *
         */
        boolean localTransactionOk = doLocalTransaction();
        if (localTransactionOk) {
            try {
                transaction.commit();
            } catch (ClientException e) {
                // You can determine whether to retry the message based on your business requirements. If you do not want to retry the message, you can query the local transaction status to commit the transaction status. 
                e.printStackTrace();
            }
        } else {
            try {
                transaction.rollback();
            } catch (ClientException e) {
                // We recommend that you record the exception information. This way, if an exception occurs during the rollback of a message, you can query the local transaction status to commit the transaction status without retrying the message. 
                e.printStackTrace();
            }
        }
    }
}