查看“Spring Boot 中使用 Kafka”的源代码

https://www.bilibili.com/video/BV1Xy4y1G7zA?p=23

=== 1.引入依赖 ===
<syntaxhighlight lang="xml">
<dependency>
	<groupId>org.springframework.kafka</groupId>
	<artifactId>spring-kafka</artifactId>
</dependency>
</syntaxhighlight>

=== 2.编写配置文件 ===
<syntaxhighlight lang="yaml">
server:
  port: 8080

spring:
  kafka:
    bootstrap-servers:
      - 192.168.137.200:9092
      - 192.168.137.200:9093
      - 192.168.137.200:9094
    producer: # 生产者
      retries: 3 # 设置大于0的值，则客户端会将发送失败的记录重新发送
      batch-size: 16384
      buffer-memory: 33554432
      acks: 1
      # 指定消息 key 和 消息体的编解码方式
      key-serializer: org.apache.kafka.common.serialization.StringSerializer
      value-serializer: org.apache.kafka.common.serialization.StringSerializer
    consumer:
      group-id: default-group
      enable-auto-commit: false
      auto-offset-reset: earliest
      key-deserializer: org.apache.kafka.common.serialization.StringDeserializer
      value-deserializer: org.apache.kafka.common.serialization.StringDeserializer
      max-poll-records: 500
    listener:
      # 当每一条记录被消费者监听器（ListenerConsumer）处理之后提交
      # RECORD

      # 当每一批 poll() 的数据被消费者监听器（ListenerConsumer）处理之后提交
      # BATCH

      # 当每一批 poll() 的数据被消费者监听器（ListenerConsumer）处理之后，距离上次提交时间大于 TIME 时提交
      # TIME

      # 当每一批 poll() 的数据被消费者监听器（ListenerConsumer）处理之后，被处理 record 数量大于等于 COUNT 时提交
      # COUNT

      # TIME | COUNT 有一个条件满足时提交
      # COUNT_TIME

      # 当每一批 poll() 的数据被消费者监听器（ListenerConsumer）处理之后，手动调用 Acknowledgment.acknowledge() 后提交
      # MANUAL

      # 手动调用 Acknowledgment.acknowledge() 后立即提交，一般使用这种
      ack-mode: MANUAL_IMMEDIATE
  redis:
    host: 127.0.0.1

</syntaxhighlight>

=== 3.编写消息生产者 ===
<syntaxhighlight lang="java">
package io.github.jihch.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/msg")
public class MyKafkaController {

    private final static String TOPIC_NAME = "my-replicated-topic";

    @Autowired
    private KafkaTemplate<String, String> kafkaTemplate;

    @RequestMapping("/send")
    public String sendMessage() {
        kafkaTemplate.send(TOPIC_NAME, 0, "key", "this is a message");
        return "send success!";
    }

}

</syntaxhighlight>

=== 4.编写消费者 ===
<syntaxhighlight lang="java">
package io.github.jihch.consumer;

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.kafka.support.Acknowledgment;
import org.springframework.stereotype.Component;

@Component
public class MyConsumer {

    @KafkaListener(topics = "my-replicated-topic", groupId = "MyGroup1")
    public void listenGroup(ConsumerRecord<String, String> record, Acknowledgment ack) {
        String value = record.value();
        System.out.println(value);
        System.out.println(record);

        //手动提交 offset
        ack.acknowledge();
    }

}

</syntaxhighlight>

=== 5.消费者中配置消费主题、分区和偏移量 ===
https://www.bilibili.com/video/BV1Xy4y1G7zA?p=24<syntaxhighlight lang="java">
    @KafkaListener(groupId = "testGroup", topicPartitions = {
            @TopicPartition(topic = "topic1", partitions = {"0", "1"}),
            @TopicPartition(topic = "topic2", partitions = "0",
            partitionOffsets = @PartitionOffset(partition = "1", initialOffset = "100"))
    }, concurrency = "3") //concurrency 就是同组下的消费者个数，就是并发消费数，建议小于等于分区数
    public void listenGroupPro(ConsumerRecord<String, String> record, Acknowledgment ack) {

        String value = record.value();
        System.out.println(value);
        System.out.println(record);

        //手动提交 offset
        ack.acknowledge();
    }
</syntaxhighlight>