RocketMQ实战–基础消息样例
生产者
基本样例部分我们使用消息生产者分别通过三种方式发送消息,同步发送、异步发送以及单向发送然后使用消费者来消费这些消息。
同步发送
同步发送消息的样例见: org.apache.rocketmq.example.simple.Producer1等待消息返回后再继续进行下面的操作。
public class Producer {
public static void main(String[] args) throws MQClientException, InterruptedException {
DefaultMQProducer producer = new DefaultMQProducer("ProducerGroupName");
producer.start();
for (int i = 0; i < 128; i++)
try {
{
Message msg = new Message("TopicTest",
"TagA",
"OrderID188",
"Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
SendResult sendResult = producer.send(msg);
System.out.printf("%s%n", sendResult);
}
} catch (Exception e) {
e.printStackTrace();
}
producer.shutdown();
}
}
异步发送
异步发送消息的样例见:org.apache.rocketmq.example.simple.AsyncProducer这个示例有个比较有趣的地方就是引入了一个countDownLatch来保证所有消息回调方法都执行完了再关闭Producer,所以从这里可以看出,RocketMQ的Producer也是一个服务端,在往Broker发送消息的时候也要作为服务端提供服务。
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);
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();
}
}
单向发送
关键点是单向发送只管发，没有返回值也没有回调。
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();
}
}
消费者
消费者消费消息有两种模式,一种是消费者主动去Broker上拉取消息的拉模式.另一种是消费者等待Broker把消息推送过来的推模式。
拉模式的样例见: org.apache.rocketmq,.example.simple.Ppullconsumer推模式的样例见: org.apache.rocketmq.example.simple.PushConsumer 通常情况下,用推模式比较简单。实际上RocketMQ的推模式也是由拉模式封装出来的。
4.7.1版本中DefaultMQPullconsumerlmpl这个消费者类已标记为过期,但是还是可以使用的。替换的类是 DefaultLitePullCconsumerlmpl
拉取消费
拉取消费较为复杂，包括多个概念，该方式主要是首先获取某个主题下的消息队列清单，并遍历各消息获取详细消息。
关键点：需要自己管理偏移量（MessageQueueOffset）
public class PullConsumer {
//用于存取偏移量
private static final Map<MessageQueue, Long> OFFSE_TABLE = new HashMap<MessageQueue, Long>();
public static void main(String[] args) throws MQClientException {
DefaultMQPullConsumer consumer = new DefaultMQPullConsumer("please_rename_unique_group_name_5");
consumer.setNamesrvAddr("127.0.0.1:9876");
consumer.start();
//某个主题下的消息队列
Set<MessageQueue> mqs = consumer.fetchSubscribeMessageQueues("broker-a");
for (MessageQueue mq : mqs) {
System.out.printf("Consume from the queue: %s%n", mq);
SINGLE_MQ:
while (true) {
try {
//拉取消息体
//pullBlockIfNotFound 中比较复杂的是第三个参数
//offset：偏移量，是消息订阅者即消费者，上次消费到的消息位点
//maxNums：最大获取消息数据量
PullResult pullResult =
consumer.pullBlockIfNotFound(mq, null, getMessageQueueOffset(mq), 32);
System.out.printf("%s%n", pullResult);
putMessageQueueOffset(mq, pullResult.getNextBeginOffset());
switch (pullResult.getPullStatus()) {
case FOUND:
break;
case NO_MATCHED_MSG:
break;
case NO_NEW_MSG:
break SINGLE_MQ;
case OFFSET_ILLEGAL:
break;
default:
break;
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
consumer.shutdown();
}
private static long getMessageQueueOffset(MessageQueue mq) {
Long offset = OFFSE_TABLE.get(mq);
if (offset != null)
return offset;
return 0;
}
private static void putMessageQueueOffset(MessageQueue mq, long offset) {
OFFSE_TABLE.put(mq, offset);
}
新的拉取模式
由于原先拉取模式的消费者对象已过期，官方提供了新的替代方案。
LitePullConsumerAssign 和 LitePullConsumerSubscribe
/**
*LitePullConsumerAssign
*/
public class LitePullConsumerAssign {
public static volatile boolean running = true;
public static void main(String[] args) throws Exception {
DefaultLitePullConsumer litePullConsumer = new DefaultLitePullConsumer("please_rename_unique_group_name");
litePullConsumer.setAutoCommit(false);
litePullConsumer.start();
Collection<MessageQueue> mqSet = litePullConsumer.fetchMessageQueues("TopicTest");
List<MessageQueue> list = new ArrayList<>(mqSet);
List<MessageQueue> assignList = new ArrayList<>();
for (int i = 0; i < list.size() / 2; i++) {
assignList.add(list.get(i));
}
litePullConsumer.assign(assignList);
litePullConsumer.seek(assignList.get(0), 10);
try {
while (running) {
List<MessageExt> messageExts = litePullConsumer.poll();
System.out.printf("%s %n", messageExts);
litePullConsumer.commitSync();
}
} finally {
litePullConsumer.shutdown();
}
}
}
/**
*LitePullConsumerSubscribe
*/
public class LitePullConsumerSubscribe {
public static volatile boolean running = true;
public static void main(String[] args) throws Exception {
DefaultLitePullConsumer litePullConsumer = new DefaultLitePullConsumer("lite_pull_consumer_test");
litePullConsumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);
litePullConsumer.subscribe("TopicTest", "*");
litePullConsumer.start();
try {
while (running) {
List<MessageExt> messageExts = litePullConsumer.poll();
System.out.printf("%s%n", messageExts);
}
} finally {
litePullConsumer.shutdown();
}
}
}
等待推送消费
等待推送消费即将消费者按照服务的方式启动，并建立消息监听器，当有消息从生产者推送时即可获取到消息。
public class PushConsumer {
public static void main(String[] args) throws InterruptedException, MQClientException {
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("CID_JODIE_1");
consumer.subscribe("TopicTest", "*");
consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);
//wrong time format 2017_0422_221800
consumer.setConsumeTimestamp("20181109221800");
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;
}
});
consumer.start();
System.out.printf("Consumer Started.%n");
}
}
原文始发于微信公众号（云户）：RocketMQ 基础消息实例解析
版权声明：本文内容由互联网用户自发贡献，该文观点仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 举报，一经查实，本站将立刻删除。
文章由极客之音整理，本文链接：https://www.bmabk.com/index.php/post/25831.html
