Spring Messaging-RocketMQ-Spring-Boot-Starter

Spring Messaging-RocketMQ-Spring-Boot-Starter
Spring Messaging
Spring Messaging是Spring Framework 4中添加的模块，是Spring与消息系统集成的一个扩展性的支持。它实现了从基于JmsTemplate的简单的使用JMS接口到异步接收消息的一整套完整的基础架构，Spring AMQP提供了该协议所要求的类似的功能集。在与Spring Boot的集成后，它拥有了自动配置能力，能够在测试和运行时与相应的消息传递系统进行集成。

单纯对于客户端而言，Spring Messaging提供了一套抽象的API或者说是约定的标准，对消息发送端和消息接收端的模式进行规定，比如消息Messaging对应的模型就包括一个消息体Payload和消息头Header。

org.springframework.messaging.Message
public interface Message<T> {

   /**
    * Return the message payload.
    */
   T getPayload();

   /**
    * Return message headers for the message (never {@code null} but may be empty).
    */
   MessageHeaders getHeaders();

}

不同的消息中间件提供商可以在这个模式下提供自己的Spring实现：在消息发送端需要实现的是一个XXXTemplate形式的Java Bean，结合Spring Boot的自动化配置选项提供多个不同的发送消息方法。
实现InitializingBean接口refresh回调afterPropertiesSet

public class RocketMQTemplate extends AbstractMessageSendingTemplate<String> implements InitializingBean, DisposableBean {
    private DefaultMQProducer producer;
    public SendResult syncSend(String destination, Message<?> message) {
        return syncSend(destination, message, producer.getSendMsgTimeout());
    }
    ...
    @Override
    public void afterPropertiesSet() throws Exception {
        if (producer != null) {
            producer.start();
        }
   }
}
public class DefaultMQProducerImpl implements MQProducerInner {
    public void start(final boolean startFactory) throws MQClientException {
        switch (this.serviceState) {
            case CREATE_JUST:
                this.serviceState = ServiceState.START_FAILED;
                this.checkConfig();
                if (!this.defaultMQProducer.getProducerGroup().equals(MixAll.CLIENT_INNER_PRODUCER_GROUP)) {
                    this.defaultMQProducer.changeInstanceNameToPID();
                }
                this.mQClientFactory = MQClientManager.getInstance().getAndCreateMQClientInstance(this.defaultMQProducer, rpcHook);
                boolean registerOK = mQClientFactory.registerProducer(this.defaultMQProducer.getProducerGroup(), this);
                if (!registerOK) {
                    this.serviceState = ServiceState.CREATE_JUST;
                    throw new MQClientException("The producer group[" + this.defaultMQProducer.getProducerGroup()
                        + "] has been created before, specify another name please." + FAQUrl.suggestTodo(FAQUrl.GROUP_NAME_DUPLICATE_URL),
                        null);
                }
                this.topicPublishInfoTable.put(this.defaultMQProducer.getCreateTopicKey(), new TopicPublishInfo());
                if (startFactory) {
                    mQClientFactory.start();
                }
                this.serviceState = ServiceState.RUNNING;
                break;
            case RUNNING:
            case START_FAILED:
            case SHUTDOWN_ALREADY:
                throw new MQClientException("The producer service state not OK, maybe started once, "
                    + this.serviceState
                    + FAQUrl.suggestTodo(FAQUrl.CLIENT_SERVICE_NOT_OK),
                    null);
            default:
                break;
        }
    
        this.mQClientFactory.sendHeartbeatToAllBrokerWithLock();
    }
}

在消息的消费端是一个XXXMessageListener接口（实现方式通常会使用一个注解来声明一个消息驱动的POJO），提供回调方法来监听和消费消息，这个接口同样可以使用Spring Boot的自动化选项和一些定制化的属性。

public interface MessageListener {
}
public interface MessageListenerConcurrently extends MessageListener {
    ConsumeConcurrentlyStatus consumeMessage(final List<MessageExt> msgs,
        final ConsumeConcurrentlyContext context);
}
public interface MessageListenerOrderly extends MessageListener {
    ConsumeOrderlyStatus consumeMessage(final List<MessageExt> msgs,
        final ConsumeOrderlyContext context);
}
public interface RocketMQListener<T> {
    void onMessage(T message);
}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RocketMQMessageListener {
    String consumerGroup();
    /**
     * Topic name.
     */
    String topic();
    ...
}
//实现SmartInitializingSingleton接口refresh回调afterSingletonsInstantiated
@Configuration
public class ListenerContainerConfiguration implements ApplicationContextAware, SmartInitializingSingleton {
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = (ConfigurableApplicationContext) applicationContext;
    }
    //处理RocketMQMessageListener注解
    @Override
    public void afterSingletonsInstantiated() {
        Map<String, Object> beans = this.applicationContext.getBeansWithAnnotation(RocketMQMessageListener.class);
    
        if (Objects.nonNull(beans)) {
            beans.forEach(this::registerContainer);
        }
    }
    private void registerContainer(String beanName, Object bean) {
        Class<?> clazz = AopProxyUtils.ultimateTargetClass(bean);
        if (!RocketMQListener.class.isAssignableFrom(bean.getClass())) {
            throw new IllegalStateException(clazz + " is not instance of " + RocketMQListener.class.getName());
        }
        RocketMQMessageListener annotation = clazz.getAnnotation(RocketMQMessageListener.class);
        validate(annotation);
        String containerBeanName = String.format("%s_%s", DefaultRocketMQListenerContainer.class.getName(),
            counter.incrementAndGet());
        GenericApplicationContext genericApplicationContext = (GenericApplicationContext) applicationContext;
        //注册并生成DefaultRocketMQListenerContainer实例
        genericApplicationContext.registerBean(containerBeanName, DefaultRocketMQListenerContainer.class,
            () -> createRocketMQListenerContainer(containerBeanName, bean, annotation));
        DefaultRocketMQListenerContainer container = genericApplicationContext.getBean(containerBeanName,
            DefaultRocketMQListenerContainer.class);
        if (!container.isRunning()) {
            try {
                container.start();
            } catch (Exception e) {
                log.error("Started container failed. {}", container, e);
                throw new RuntimeException(e);
            }
        }
        log.info("Register the listener to container, listenerBeanName:{}, containerBeanName:{}", beanName, containerBeanName);
    }
    
    private DefaultRocketMQListenerContainer createRocketMQListenerContainer(String name, Object bean, RocketMQMessageListener annotation) {
        DefaultRocketMQListenerContainer container = new DefaultRocketMQListenerContainer();
        String nameServer = environment.resolvePlaceholders(annotation.nameServer());
        nameServer = StringUtils.isEmpty(nameServer) ? rocketMQProperties.getNameServer() : nameServer;
        String accessChannel = environment.resolvePlaceholders(annotation.accessChannel());
        container.setNameServer(nameServer);
        if (!StringUtils.isEmpty(accessChannel)) {
            container.setAccessChannel(AccessChannel.valueOf(accessChannel));
        }
        container.setTopic(environment.resolvePlaceholders(annotation.topic()));
        container.setConsumerGroup(environment.resolvePlaceholders(annotation.consumerGroup()));
        container.setRocketMQMessageListener(annotation);
        container.setRocketMQListener((RocketMQListener) bean);
        container.setObjectMapper(objectMapper);
        container.setName(name);  // REVIEW ME, use the same clientId or multiple?
        return container;
    }
}
//实现InitializingBean接口refresh回调afterPropertiesSet
public class DefaultRocketMQListenerContainer implements InitializingBean,
    RocketMQListenerContainer, SmartLifecycle, ApplicationContextAware {
    @Override
    public void afterPropertiesSet() throws Exception {
        initRocketMQPushConsumer();
        this.messageType = getMessageType();
    }
    private void initRocketMQPushConsumer() throws MQClientException {
        Assert.notNull(rocketMQListener, "Property 'rocketMQListener' is required");
        Assert.notNull(consumerGroup, "Property 'consumerGroup' is required");
        Assert.notNull(nameServer, "Property 'nameServer' is required");
        Assert.notNull(topic, "Property 'topic' is required");
        RPCHook rpcHook = RocketMQUtil.getRPCHookByAkSk(applicationContext.getEnvironment(),
            this.rocketMQMessageListener.accessKey(), this.rocketMQMessageListener.secretKey());
        boolean enableMsgTrace = rocketMQMessageListener.enableMsgTrace();
        if (Objects.nonNull(rpcHook)) {
            consumer = new DefaultMQPushConsumer(consumerGroup, rpcHook, new AllocateMessageQueueAveragely(),
                enableMsgTrace, this.applicationContext.getEnvironment().
                resolveRequiredPlaceholders(this.rocketMQMessageListener.customizedTraceTopic()));
            consumer.setVipChannelEnabled(false);
            consumer.setInstanceName(RocketMQUtil.getInstanceName(rpcHook, consumerGroup));
        } else {
            log.debug("Access-key or secret-key not configure in " + this + ".");
            consumer = new DefaultMQPushConsumer(consumerGroup, enableMsgTrace,
                    this.applicationContext.getEnvironment().
                    resolveRequiredPlaceholders(this.rocketMQMessageListener.customizedTraceTopic()));
        }
        String customizedNameServer = this.applicationContext.getEnvironment().resolveRequiredPlaceholders(this.rocketMQMessageListener.nameServer());
        if (customizedNameServer != null) {
            consumer.setNamesrvAddr(customizedNameServer);
        } else {
            consumer.setNamesrvAddr(nameServer);
        }
        if (accessChannel != null) {
            consumer.setAccessChannel(accessChannel);
        }
        consumer.setConsumeThreadMax(consumeThreadMax);
        if (consumeThreadMax < consumer.getConsumeThreadMin()) {
            consumer.setConsumeThreadMin(consumeThreadMax);
        }
        consumer.setConsumeTimeout(consumeTimeout);
        consumer.setInstanceName(this.name);
        switch (messageModel) {
            case BROADCASTING:
                consumer.setMessageModel(org.apache.rocketmq.common.protocol.heartbeat.MessageModel.BROADCASTING);
                break;
            case CLUSTERING:
                consumer.setMessageModel(org.apache.rocketmq.common.protocol.heartbeat.MessageModel.CLUSTERING);
                break;
            default:
                throw new IllegalArgumentException("Property 'messageModel' was wrong.");
        }
        switch (selectorType) {
            case TAG:
                consumer.subscribe(topic, selectorExpression);
                break;
            case SQL92:
                consumer.subscribe(topic, MessageSelector.bySql(selectorExpression));
                break;
            default:
                throw new IllegalArgumentException("Property 'selectorType' was wrong.");
        }
        switch (consumeMode) {
            case ORDERLY:
                consumer.setMessageListener(new DefaultMessageListenerOrderly());
                break;
            case CONCURRENTLY:
                consumer.setMessageListener(new DefaultMessageListenerConcurrently());
                break;
            default:
                throw new IllegalArgumentException("Property 'consumeMode' was wrong.");
        }
        if (rocketMQListener instanceof RocketMQPushConsumerLifecycleListener) {
            ((RocketMQPushConsumerLifecycleListener) rocketMQListener).prepareStart(consumer);
        }
    }
}

总结：在Apache RocketMQ生态中，RocketMQ-Spring-Boot-Starter（下文简称RocketMQ-Spring）就是一个支持Spring Messaging API标准的项目。该项目把RocketMQ的客户端使用Spring Boot的方式进行了封装，可以让用户通过简单的annotation和标准的Spring Messaging API编写代码来进行消息的发送和消费，也支持扩展出RocketMQ原生API来支持更加丰富的消息类型。