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TDMQ for RocketMQ
DocumentationTDMQ for RocketMQRocketMQ 4.xSDK DocumentationAccess over TCPSDK for JavaSending and Receiving General Messages
Sending and Receiving General Messages
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Last updated: 2023-10-30 10:38:25
Sending and Receiving General Messages
Last updated: 2023-10-30 10:38:25
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Overview

This document describes how to use open-source SDK to send and receive messages by using the SDK for Java as an example and helps you better understand the message sending and receiving processes.

Prerequisites

You have created or prepared the required resources as instructed in Resource Creation and Preparation.
You have installed JDK 1.8 or later.
You have installed Maven 2.5 or later.
You have downloaded the demo or obtained the demo in TencentCloud/rocketmq-demo in GitHub.

Directions

Step 1. Install the Java dependent library

Introduce dependencies in a Java project and add the following dependencies to the pom.xml file. This document uses a Maven project as an example.
Note
The dependency version must be v4.9.3 or later, preferably v4.9.4.
<!-- in your <dependencies> block -->
  <dependency>
      <groupId>org.apache.rocketmq</groupId>
      <artifactId>rocketmq-client</artifactId>
      <version>4.9.4</version>
  </dependency>
  
  <dependency>
      <groupId>org.apache.rocketmq</groupId>
      <artifactId>rocketmq-acl</artifactId>
      <version>4.9.4</version>
  </dependency>

Step 2. Produce messages

Creating a message producer

// Instantiate the message producer
   DefaultMQProducer producer = new DefaultMQProducer(
       groupName,
       new AclClientRPCHook(new SessionCredentials(accessKey, secretKey)) // ACL permission
   );
   // Set the Nameserver address
   producer.setNamesrvAddr(nameserver);
   // Start the producer instance
   producer.start();

Parameter
Description
groupName
Producer group name. We recommend that you use the corresponding topic name as the producer name.
accessKey
Role token, which can be copied in the Token column on the Role Management page.

secretKey
Role name, which can be copied on the Role Management page.
nameserver
Cluster access address, which can be obtained from Access Address in the Operation column on the Cluster page in the console. The namespace access address can be obtained under the Namespace tab on the Cluster page.

Sending messages

Messages can be sent in the sync, async, or one-way mode.
Sync sending
for (int i = 0; i < 10; i++) {
          // Create a message instance and set the topic and message content
          Message msg = new Message(topic_name, "TAG", ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET));
          // Send the message
          SendResult sendResult = producer.send(msg);
          System.out.printf("%s%n", sendResult);
      }
Parameter
Description
topic_name
Topic name, which can be copied under the Topic tab on the Cluster page in the console.
TAG
A parameter used to set the message tag.
Async sending
// Disable retry upon sending failures
      producer.setRetryTimesWhenSendAsyncFailed(0);
      // Set the number of messages to be sent
      int messageCount = 10;
      final CountDownLatch countDownLatch = new CountDownLatch(messageCount);
      for (int i = 0; i < messageCount; i++) {
          try {
              final int index = i;
              // Create a message instance and set the topic and message content
              Message msg = new Message(topic_name, "TAG", ("Hello rocketMq " + index).getBytes(RemotingHelper.DEFAULT_CHARSET));
              producer.send(msg, new SendCallback() {
                  @Override
                  public void onSuccess(SendResult sendResult) {
                      // Logic for message sending successes
                      countDownLatch.countDown();
                      System.out.printf("%-10d OK %s %n", index, sendResult.getMsgId());
                  }
      
                  @Override
                  public void onException(Throwable e) {
                      // Logic for message sending failures
                      countDownLatch.countDown();
                      System.out.printf("%-10d Exception %s %n", index, e);
                      e.printStackTrace();
                  }
              });
          } catch (Exception e){
              e.printStackTrace();
          }
      }
      countDownLatch.await(5, TimeUnit.SECONDS);
Parameter
Description
topic_name
Topic name, which can be copied under the Topic tab on the Cluster page in the console.
TAG
A parameter used to set the message tag.
One-way sending
for (int i = 0; i < 10; i++) {
         // Create a message instance and set the topic and message content
         Message msg = new Message(topic_name, "TAG", ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET));
         // Send one-way messages
         producer.sendOneway(msg);
     }
Parameter
Description
topic_name
Topic name, which can be copied under the Topic tab on the Cluster page in the console.
TAG
A parameter used to set the message tag.
Note
For batch sending and other cases, see TencentCloud/rocketmq-demo in GitHub or the Apache RocketMQ documentation.

Step 3. Consume messages

Creating a consumer

TDMQ for RocketMQ supports two consumption modes: push and pull. The push mode is recommended.
// Instantiate the consumer
        DefaultMQPushConsumer pushConsumer = new DefaultMQPushConsumer(
            groupName,                                              
            new AclClientRPCHook(new SessionCredentials(accessKey, secretKey))); // ACL permission
        // Set the Nameserver address
        pushConsumer.setNamesrvAddr(nameserver);
Parameter
Description
groupName
Consumer group name, which can be copied under the Group tab on the Cluster page in the console.
nameserver
Cluster access address, which can be obtained from Access Address in the Operation column on the Cluster page in the console. The namespace access address can be obtained under the Namespace tab on the Cluster page.
secretKey
Role name, which can be copied on the Role Management page.
accessKey
Role token, which can be copied in the Token column on the Role Management page.


Subscribing to messages

The subscription modes vary by consumption mode.
// Subscribe to a topic
      pushConsumer.subscribe(topic_name, "*");
      // Register a callback implementation class to process messages pulled from the broker
      pushConsumer.registerMessageListener((MessageListenerConcurrently) (msgs, context) -> {
          // Message processing logic
          System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);
          // Mark the message as being successfully consumed and return the consumption status
          return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
      });
      // Start the consumer instance
      pushConsumer.start();
Parameter
Description
topic_name
Topic name, which can be copied under the Topic tab on the Cluster page in the console.
"*"
If the subscription expression is left empty or specified as asterisk (*), all messages are subscribed to. tag1 || tag2 || tag3 means subscribing to multiple types of tags.

Step 4. View consumption details

Log in to the TDMQ console, go to the Cluster > Group page, and view the list of clients connected to the consumer group. Click Consumer Details in the Operation column to view consumer details.

Note
Above is a brief introduction to message publishing and subscription. For more information, see TencentCloud/rocketmq-demo or the Apache RocketMQ documentation.

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