SpringBoot整合RocketMQ遇到的坑怎么解决

应用场景

在实现RocketMQ消费时，一般会用到@RocketMQMessageListener注解定义Group、Topic以及selectorExpression（数据过滤、选择的规则）为了能支持动态筛选数据，一般都会使用表达式，然后通过apollo或者cloud config进行动态切换。

引入依赖

 <!-- RocketMq Spring Boot Starter-->
 <dependency>
  <groupId>org.apache.rocketmq</groupId>
  <artifactId>rocketmq-spring-boot-starter</artifactId>
  <version>2.0.4</version>
  </dependency>

消费者代码

@RocketMQMessageListener(consumerGroup = "${rocketmq.group}",topic ="${rocketmq.topic}",selectorExpression = "${rocketmq.selectorExpression}")
public class Consumer implements RocketMQListener<String> {
    @Override
    public void onMessage(String s) {
        System.out.println("消费到的数据为："+s);
    }
}

问题排查

RocketMQMessageListener整个注解默认selectorExpression为*，表示接收当前Topic下的所有数据，如果我们想对tags进行动态配置，在使用${rocketmq.selectorExpression}表达式时会发现所有数据全被过滤了，跟踪源码（ListenerContainerConfiguration.java）发现在创建listener时selectorExpression的数据在通environment环境变量中获取对应的数据后又被覆盖了，导致整个过滤条件被变更为表达式。

@Override
    public void afterSingletonsInstantiated() {
    	// 获取所有所有使用了RocketMQMessageListener注解的bean
        Map<String, Object> beans = this.applicationContext.getBeansWithAnnotation(RocketMQMessageListener.class);
        if (Objects.nonNull(beans)) {
        	// 循环注册容器
            beans.forEach(this::registerContainer);
        }
    }
    private void registerContainer(String beanName, Object bean) {
        Class<?> clazz = AopProxyUtils.ultimateTargetClass(bean);
		// 校验当前bean是否实现了RocketMQListener接口
        if (!RocketMQListener.class.isAssignableFrom(bean.getClass())) {
            throw new IllegalStateException(clazz + " is not instance of " + RocketMQListener.class.getName());
        }
		// 获取bean上的annotation
        RocketMQMessageListener annotation = clazz.getAnnotation(RocketMQMessageListener.class);
		// 解析group及topic，可支持表达式
        String consumerGroup = this.environment.resolvePlaceholders(annotation.consumerGroup());
        String topic = this.environment.resolvePlaceholders(annotation.topic());
        boolean listenerEnabled =
            (boolean)rocketMQProperties.getConsumer().getListeners().getOrDefault(consumerGroup, Collections.EMPTY_MAP)
                .getOrDefault(topic, true);
        if (!listenerEnabled) {
            log.debug(
                "Consumer Listener (group:{},topic:{}) is not enabled by configuration, will ignore initialization.",
                consumerGroup, topic);
            return;
        }
        validate(annotation);
        String containerBeanName = String.format("%s_%s", DefaultRocketMQListenerContainer.class.getName(),
            counter.incrementAndGet());
        GenericApplicationContext genericApplicationContext = (GenericApplicationContext)applicationContext;
		// 注册bean的，调用createRocketMQListenerContainer
        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();        
        container.setRocketMQMessageListener(annotation);        
        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()));
        // 此处已经根据表达式将数据取出
        String tags = environment.resolvePlaceholders(annotation.selectorExpression());
        if (!StringUtils.isEmpty(tags)) {
            container.setSelectorExpression(tags);
        }
        container.setConsumerGroup(environment.resolvePlaceholders(annotation.consumerGroup()));
        // 此处将SelectorExpression的数据覆盖成了表达式
        container.setRocketMQMessageListener(annotation);
        container.setRocketMQListener((RocketMQListener)bean);
        container.setObjectMapper(objectMapper);
        container.setMessageConverter(rocketMQMessageConverter.getMessageConverter());
        container.setName(name);  // REVIEW ME, use the same clientId or multiple?
        return container;
    }

问题解决

因为ListenerContainerConfiguration类是实现了SmartInitializingSingleton接口的afterSingletonsInstantiated方法，我们可以通过反射对selectorExpression的数据在ListenerContainerConfiguration进行初始化前进行解析并赋值回去。

/**
 * 在springboot初始化后，RocketMQ容器初始化前利用反射动态改变数据
**/
@Configuration
public class ChangeSelectorExpressionBeforeMQInit implements InitializingBean {
    @Autowired
    private ApplicationContext applicationContext;
    @Autowired
    private StandardEnvironment environment;
    @Override
    public void afterPropertiesSet() throws Exception {
        Map<String,Object> beans =applicationContext.getBeansWithAnnotation(RocketMQMessageListener.class);
        for (Object bean : beans.values()){
            Class<?> clazz = AopProxyUtils.ultimateTargetClass(bean);
            if (!RocketMQListener.class.isAssignableFrom(bean.getClass())) {
                continue;
            }
            RocketMQMessageListener annotation = clazz.getAnnotation(RocketMQMessageListener.class);
            InvocationHandler invocationHandler = Proxy.getInvocationHandler(annotation);
            Field field = invocationHandler.getClass().getDeclaredField("memberValues");
            field.setAccessible(true);
            Map<String, Object> memberValues = (Map<String, Object>) field.get(invocationHandler);
            for (Map.Entry<String,Object> entry: memberValues.entrySet()) {
                if(Objects.nonNull(entry)){
                    memberValues.put(entry.getKey(),environment.resolvePlaceholders(String.valueOf(entry.getValue())));
                }
            }
        }
    }
}

初次之外，在2.1.0版本的依赖包中已经修复了此Bug，在不造成依赖冲突的前提下，建议使用2.1.0以上的版本包。

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