簡單消息示例

• 使用RocketMQ以三種方式發送消息：可靠的同步，可靠的異步和單向傳輸。
• 使用RocketMQ消費消息

1. 引入依賴
   maven:

<code> <dependency>
    <groupid>org.apache.rocketmq/<groupid>
    <artifactid>rocketmq-client/<artifactid>
    <version>4.3.0/<version>
/<dependency>
/<code>

gradle:

<code>compile 'org.apache.rocketmq:rocketmq-client:4.3.0'
/<code>

2. 發送消息
   同步
   重要的通知消息，我們需要保證消息傳遞的可靠性，比如SMS服務。

<code>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();
    }
}
/<code>

異步
異步通常用於需要快速返回，對時間比較敏感的業務場景中。

<code>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);
        for (int i = 0; i < 100; i++) {
                final int index = i;
                //Create a message instance, specifying topic, tag and message body.
                Message msg = new Message("TopicTest",
                    "TagA",
                    "OrderID188",
                    "Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
                producer.send(msg, new SendCallback() {
                    @Override
                    public void onSuccess(SendResult sendResult) {
                        System.out.printf("%-10d OK %s %n", index,
                            sendResult.getMsgId());
                    }
                    @Override
                    public void onException(Throwable e) {
                        System.out.printf("%-10d Exception %s %n", index, e);
                        e.printStackTrace();
                    }
                });
        }
        //Shut down once the producer instance is not longer in use.
        producer.shutdown();
    }
}
/<code>

單項傳輸
單向傳輸用於要求中等可靠性的情況，例如日誌收集。

<code>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);
        }
        //Shut down once the producer instance is not longer in use.
        producer.shutdown();
    }
}
/<code>

3. 消費消息

<code>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");
    }
}/<messageext>/<code>

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