OpenMessaging是阿里牵头发起的分布式消息模型标准，其api规范首先在rocketmq中落地实现。 通过这个标准可以简化各种消息中间件的高复杂性和不兼容性，提升消息中间件服务的易用性。

maven 工程添加库

<dependency>
    <groupId>org.apache.rocketmq</groupId>
    <artifactId>rocketmq-client</artifactId>
    <version>4.4.0</version>
</dependency>

gradle 工程添加库

compile 'org.apache.rocketmq:rocketmq-client:4.4.0'

注意：

客户端版本要和服务端版本的一致，或者会发生一些奇怪的问题：

我遇到过版本不一致会发生，消息无法确认消息消费，也就是说 客户端已经消费了，也提交成功了，但是服务端没有同步到！

要到控制台创建 Topic 队列名称

发送消息

public class OMSProducer {
    public static void main(String[] args) {
        final MessagingAccessPoint messagingAccessPoint = MessagingAccessPointFactory
            .getMessagingAccessPoint("openmessaging:rocketmq://IP1:9876,IP2:9876/namespace");

        final Producer producer = messagingAccessPoint.createProducer();

        messagingAccessPoint.startup();
        System.out.printf("MessagingAccessPoint startup OK%n");

        producer.startup();
        System.out.printf("Producer startup OK%n");

        {
            Message message = producer.createBytesMessageToTopic("OMS_HELLO_TOPIC", "OMS_HELLO_BODY".getBytes(Charset.forName("UTF-8")));
            SendResult sendResult = producer.send(message);
            System.out.printf("Send sync message OK, msgId: %s%n", sendResult.messageId());
        }

        {
            final Promise<SendResult> result = producer.sendAsync(producer.createBytesMessageToTopic("OMS_HELLO_TOPIC", "OMS_HELLO_BODY".getBytes(Charset.forName("UTF-8"))));
            result.addListener(new PromiseListener<SendResult>() {
                @Override
                public void operationCompleted(Promise<SendResult> promise) {
                    System.out.printf("Send async message OK, msgId: %s%n", promise.get().messageId());
                }

                @Override
                public void operationFailed(Promise<SendResult> promise) {
                    System.out.printf("Send async message Failed, error: %s%n", promise.getThrowable().getMessage());
                }
            });
        }

        {
            producer.sendOneway(producer.createBytesMessageToTopic("OMS_HELLO_TOPIC", "OMS_HELLO_BODY".getBytes(Charset.forName("UTF-8"))));
            System.out.printf("Send oneway message OK%n");
        }

        producer.shutdown();
        messagingAccessPoint.shutdown();
    }
}

拉取消息消费

public class OMSPullConsumer {
    public static void main(String[] args) {
        final MessagingAccessPoint messagingAccessPoint = MessagingAccessPointFactory
            .getMessagingAccessPoint("openmessaging:rocketmq://IP1:9876,IP2:9876/namespace");

        final PullConsumer consumer = messagingAccessPoint.createPullConsumer("OMS_HELLO_TOPIC",
            OMS.newKeyValue().put(NonStandardKeys.CONSUMER_GROUP, "OMS_CONSUMER"));

        messagingAccessPoint.startup();
        System.out.printf("MessagingAccessPoint startup OK%n");

        consumer.startup();
        System.out.printf("Consumer startup OK%n");

        Message message = consumer.poll();
        if (message != null) {
            String msgId = message.headers().getString(MessageHeader.MESSAGE_ID);
            System.out.printf("Received one message: %s%n", msgId);
            consumer.ack(msgId);
        }

        consumer.shutdown();
        messagingAccessPoint.shutdown();
    }
}

通过推送消费消息

public class OMSPushConsumer {
    public static void main(String[] args) {
        final MessagingAccessPoint messagingAccessPoint = MessagingAccessPointFactory
            .getMessagingAccessPoint("openmessaging:rocketmq://IP1:9876,IP2:9876/namespace");

        final PushConsumer consumer = messagingAccessPoint.
            createPushConsumer(OMS.newKeyValue().put(NonStandardKeys.CONSUMER_GROUP, "OMS_CONSUMER"));

        messagingAccessPoint.startup();
        System.out.printf("MessagingAccessPoint startup OK%n");

        Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
            @Override
            public void run() {
                consumer.shutdown();
                messagingAccessPoint.shutdown();
            }
        }));

        consumer.attachQueue("OMS_HELLO_TOPIC", new MessageListener() {
            @Override
            public void onMessage(final Message message, final ReceivedMessageContext context) {
                System.out.printf("Received one message: %s%n", message.headers().getString(MessageHeader.MESSAGE_ID));
                context.ack();
            }
        });

    }
}