有以下3种方式发送RocketMQ消息

• 可靠同步发送 reliable synchronous
• 可靠异步发送 reliable asynchronous
• 单向发送 one-way transmission

可靠同步发送

主要运用在比较重要一点消息传递/通知等业务

public class SyncProducer {
    public static void main(String[] args) throws Exception {
        DefaultMQProducer producer = new
            DefaultMQProducer("test");
        producer.start();
        for (int i = 0; i < 100; i++) {
            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();
    }
}

可靠异步发送

通常用于对发送消息响应时间要求更高/更快的场景

public class AsyncProducer {
    public static void main(
        String[] args) throws MQClientException, InterruptedException, UnsupportedEncodingException {
        DefaultMQProducer producer = new DefaultMQProducer("Jodie_Daily_test");
        producer.start();
        producer.setRetryTimesWhenSendAsyncFailed(0);

        for (int i = 0; i < 10000000; i++) {
            try {
                final int index = i;
                Message msg = new Message("Jodie_topic_1023",
                    "TagA",
                    "OrderID188",
                    "Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
                    //重点在这里 异步发送回调
                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();
                    }
                });
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        producer.shutdown();
    }
}

单向发送

适用于某些耗时非常短，但对可靠性要求并不高的场景，例如日志收集。

只发送消息，不等待服务器响应，只发送请求不等待应答。此方式发送消息的过程耗时非常短，一般在微秒级别。

public class OnewayProducer {
    public static void main(String[] args) throws Exception{
        DefaultMQProducer producer = new DefaultMQProducer("Test");
        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();
    }
}