Simple Message Example
- Use RocketMQ to send messages in three ways: reliable synchronous, reliable asynchronous, and one-way transmission.
- Use RocketMQ to consume messages
1. Add Dependency
maven:
<dependency>
<groupId>org.apache.rocketmq</groupId>
<artifactId>rocketmq-client</artifactId>
<version>4.3.0</version>
</dependency>
gradle:
compile 'org.apache.rocketmq:rocketmq-client:4.3.0'
2.1 Send Messages Synchronously
Reliable synchronous transmission is used in extensive scenes, such as important notification messages, SMS notification, SMS marketing system, etc..
public class SyncProducer {
public static void main(String[] args) throws Exception {
//Instantiate with a producer group name.
DefaultMQProducer producer = new
DefaultMQProducer("please_rename_unique_group_name");
// Specify name server addresses.
producer.setNamesrvAddr("localhost:9876");
//Launch the instance.
producer.start();
for (int i = 0; i < 100; i++) {
//Create a message instance, specifying topic, tag and message body.
Message msg = new Message("TopicTest" /* Topic */,
"TagA" /* Tag */,
("Hello RocketMQ " +
i).getBytes(RemotingHelper.DEFAULT_CHARSET) /* Message body */
);
//Call send message to deliver message to one of brokers.
SendResult sendResult = producer.send(msg);
System.out.printf("%s%n", sendResult);
}
//Shut down once the producer instance is not longer in use.
producer.shutdown();
}
}
2.2 Send Messages Asynchronously
Asynchronous transmission is generally used in response time sensitive business scenarios.
public class AsyncProducer {
public static void main(String[] args) throws Exception {
//Instantiate with a producer group name.
DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
// Specify name server addresses.
producer.setNamesrvAddr("localhost:9876");
//Launch the instance.
producer.start();
producer.setRetryTimesWhenSendAsyncFailed(0);
int messageCount = 100;
final CountDownLatch countDownLatch = new CountDownLatch(messageCount);
for (int i = 0; i < messageCount; i++) {
try {
final int index = i;
Message msg = new Message("Jodie_topic_1023",
"TagA",
"OrderID188",
"Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
producer.send(msg, new SendCallback() {
@Override
public void onSuccess(SendResult sendResult) {
countDownLatch.countDown();
System.out.printf("%-10d OK %s %n", index, sendResult.getMsgId());
}
@Override
public void onException(Throwable e) {
countDownLatch.countDown();
System.out.printf("%-10d Exception %s %n", index, e);
e.printStackTrace();
}
});
} catch (Exception e) {
e.printStackTrace();
}
}
countDownLatch.await(5, TimeUnit.SECONDS);
producer.shutdown();
}
}
2.3 Send Messages in One-way Mode
One-way transmission is used for cases requiring moderate reliability, such as log collection.
public class OnewayProducer {
public static void main(String[] args) throws Exception{
//Instantiate with a producer group name.
DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
// Specify name server addresses.
producer.setNamesrvAddr("localhost:9876");
//Launch the instance.
producer.start();
for (int i = 0; i < 100; i++) {
//Create a message instance, specifying topic, tag and message body.
Message msg = new Message("TopicTest" /* Topic */,
"TagA" /* Tag */,
("Hello RocketMQ " +
i).getBytes(RemotingHelper.DEFAULT_CHARSET) /* Message body */
);
//Call send message to deliver message to one of brokers.
producer.sendOneway(msg);
}
//Wait for sending to complete
Thread.sleep(5000);
producer.shutdown();
}
}
3. Consume Messages
public class Consumer {
public static void main(String[] args) throws InterruptedException, MQClientException {
// Instantiate with specified consumer group name.
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name");
// Specify name server addresses.
consumer.setNamesrvAddr("localhost:9876");
// Subscribe one more more topics to consume.
consumer.subscribe("TopicTest", "*");
// Register callback to execute on arrival of messages fetched from brokers.
consumer.registerMessageListener(new MessageListenerConcurrently() {
@Override
public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs,
ConsumeConcurrentlyContext context) {
System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
//Launch the consumer instance.
consumer.start();
System.out.printf("Consumer Started.%n");
}
}
4. Find More
Alternatively, you could get more examples from: https://github.com/apache/rocketmq/tree/master/example
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