依赖

 <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-streams</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.kafka</groupId>
            <artifactId>spring-kafka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.kafka</groupId>
            <artifactId>spring-kafka-test</artifactId>
            <scope>test</scope>

配置文件

spring.kafka.listener.concurrency=3
在spring-kafka在运行时会启动两类线程，一类是Consumer线程，另一类是Listener线程。前者用来直接调用kafka-client的poll()方法获取消息，后者才是调用我们代码中标有@KafkaListener注解方法的线程。如果直接使用kafka-client的话，那么正常的写法是一个while循环，在循环里面调用poll()，然后处理消息，这在kafka broker看来就是一个Consumer。如果你想用多个Consumer, 除了多启动几个进程以外，也可以在一个进程使用多个线程执行此while()循环。spring-kafka就是这么干的。

对于spring.kafka.listener.concurrency=3这个参数来说，它设置的是每个@KafkaListener的并发个数。每添加一个@KafkaListener, spring-kafka都会启动一条Consumer线程来监听这些topic(注解可以指定监听多个topic), 然后再启动spring.kafka.listener.concurrency条线程来真正执行你的Listener

此段来自：https://blog.csdn.net/dshf_1/article/details/103203920

server:
  port: 8080

spring:
  kafka:
    bootstrap-servers: ip:9092
    consumer:
      group-id: test-consumer
    producer:
      batch-size: 16384
      buffer-memory: 33554432
      key-serializer: org.apache.kafka.common.serialization.StringSerializer
      retries: 0
      value-serializer: org.apache.kafka.common.serialization.StringSerializer

provder

import org.apache.kafka.clients.producer.ProducerRecord;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;


/**
 * @author: zhangxirui
 * @date: 2021-02-07 9:27
 * @version: 1.0
 */
@Component
@EnableScheduling
public class KafkaProvder {
    @Autowired
    private KafkaTemplate kafkaTemplate;

    @Scheduled(cron = "* * * * * ?")
    public void producerr() {
        for (int i = 0; i < 10; i++) {
            kafkaTemplate.send(new ProducerRecord<String, String>("my-topic", "hello" + i, "java" + i));
        }
    }
}

listen

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.stereotype.Component;
import java.util.Optional;


/**
 * @author: zhangxirui
 * @date: 2021-02-07 9:27
 * @version: 1.0
 */
@Component
public class KafkaListenerr {

    @KafkaListener(topics = {"my-topic"})
    public void listen(ConsumerRecord<?, ?> record) {
        Optional<?> kafkaMessage = Optional.ofNullable(record.value());
        if (kafkaMessage.isPresent()) {
            System.out.println("消息接收成功");
            Object message = kafkaMessage.get();
            System.out.println("record =" + record);
            System.out.println("message =" + message);
        }
    }
}