注解@KafkaListener批量接收消息

之前介绍了如何在SpringBoot中集成Kafka,但是默认情况下，@KafkaListener都是一条一条消费，如果想要一次消费一个批量的话，我们都知道，在kafka原生的API可以通过poll(num)来获取一次获取num条消息：

那么使用在Springboot中使用@KafkaListener能否实现批量监听呢？

看了spring-kafka的官方文档https://docs.spring.io/spring-kafka/reference/html/_reference.html介绍，可以知道自1.1版本之后，@KafkaListener开始支持批量消费，只需要设置batchListener参数为true。

 @Bean
 public KafkaListenerContainerFactory<?> batchFactory() {
    ConcurrentKafkaListenerContainerFactory<Integer, String> factory =
                new ConcurrentKafkaListenerContainerFactory<>();
    factory.setConsumerFactory(consumerFactory());
    factory.setConcurrency(1);
    factory.setBatchListener(true);//设置为批量消费，每个批次数量在Kafka配置参数中设置ConsumerConfig.MAX_POLL_RECORDS_CONFIG
    factory.getContainerProperties().setAckMode(AckMode.MANUAL_IMMEDIATE);//设置提交偏移量的方式
    return factory;
}

@Bean
public Map<String, Object> consumerConfigs() {
        Map<String, Object> props = new HashMap<>();
        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
        props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, false);
        props.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "100");
        props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, "15000");
        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        props.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);
        props.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, maxPollRecords);//每一批数量
        props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, autoOffsetReset);
        return props;
}

开始监听，批量消费后采用JPA的方式批量写入数据库，这里containerFactory = “batchFactory”要指定为批量消费。

@KafkaListener(topics = "${tgs.kafka.topics}", containerFactory = "batchFactory")
public void listen(List<ConsumerRecord<?, ?>> records, Acknowledgment ack) {
        logger.info("records.size: " + records.size() + " in all");
        List<B_ZDRYGK_ZDRYXX_FJ_HCB1> list = new ArrayList<B_ZDRYGK_ZDRYXX_FJ_HCB1>();
        ObjectMapper mapper = new ObjectMapper();
        B_ZDRYGK_ZDRYXX_FJ_HCB1 b_zdrygk_zdryxx_fj_hcb1 =null;
        for (ConsumerRecord<?, ?> record : records) {
            try {
                b_zdrygk_zdryxx_fj_hcb1 = mapper.readValue(record.value().toString(), B_ZDRYGK_ZDRYXX_FJ_HCB1.class);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (null != b_zdrygk_zdryxx_fj_hcb1) {
                list.add(b_zdrygk_zdryxx_fj_hcb1);
            }
        }
        try {
            List<B_ZDRYGK_ZDRYXX_FJ_HCB1> hcb1List = b_ZDRYGK_ZDRYXX_FJ_HCB1Repository.save(list);
            b_ZDRYGK_ZDRYXX_FJ_HCB1Repository.flush();
            logger.info("flush size: " + hcb1List.size());
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
          logger.info("start commit offset");
          ack.acknowledge();//手动提交偏移量
          logger.info("stop commit offset");
     } 
}