springboot集成kafka

springboot 集成 kafka 的方法非常简单，直接上代码。

    org.springframework.kafka
    spring-kafka

引入此包后，通过 springboot 的自动装配机制，KafkaAutoConfiguration 类会被加载到 ioc 容器，同时它里面定义的一些 bean 也会被加载，比如 kafkaTemplate，后面发送消息时就会用到。

spring:
  kafka:
    bootstrap-servers: 127.0.0.1:9092
    listener:
      missing-topics-fatal: false
    producer:
      retries: 0
      batch-size: 16384
      buffer-memory: 33554432
      key-serializer: org.apache.kafka.common.serialization.StringSerializer
      value-serializer: org.apache.kafka.common.serialization.StringSerializer
    consumer:
      group-id: demo-group 
      auto-commit-interval: 100
      enable-auto-commit: true
      auto-offset-reset: earliest
      key-deserializer: org.apache.kafka.common.serialization.StringDeserializer
      value-deserializer: org.apache.kafka.common.serialization.StringDeserializer

• missing-topics-fatal 如果设置为 true，当消费者监听的主题不存在时，会报错。所以需要设置为 false
• consumer 的 group-id 是消费者组，自行设置
• key 的序列化器和发序列化器，需要对应。value的同理

发送端通过 kafkaTemplate.send 方法发送消息

@Autowired
private KafkaTemplate kafkaTemplate;

private void sendMailMessage() {
	String[] ccMail = getMailReceiver();
	MailEntity mailEntity = new MailEntity();
	mailEntity.setReceiver("xxx.qq.com");
	mailEntity.setCc(ccMail);
	mailEntity.setSubject("测试邮件");
	mailEntity.setContent("测试邮件");
	kafkaTemplate.send("mail-send", JSON.toJSonString(mailEntity));
}

消费端通过 @KafkaListener 注解，并指定 topics 参数来接收消息。record.value() 中可以取得消息体的内容。 

@Component
public class MailSendConsumer {
    @Autowired
    private JavaMailSender javaMailSender;

    @KafkaListener(topics = { "mail-send" })
    public void sendMail(ConsumerRecord record){
        MailEntity entity = JSON.parseObject(record.value(), MailEntity.class);
        SimpleMailMessage message = new SimpleMailMessage();
        message.setFrom(sender);
        message.setTo(entity.getReceiver());
        message.setCc(entity.getCc());
        message.setSubject(entity.getSubject());
        message.setText(entity.getContent());
        javaMailSender.send(message);
    }
}