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**/@Configurationpublic 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。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。
发现一种久违的感动。
