Kafka系列之第一个kafka程序

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本文介绍如何使用Spring Boot搭建Kafka环境，包括配置Kafka生产者与消费者，并通过示例代码演示消息的发送与接收过程。

1.创建一个springboot的工程

2.pom.xml添加原始的kafka maven依赖

<dependency>
    <groupId>org.apache.kafka</groupId>
    <artifactId>kafka_2.12</artifactId>
    <version>2.1.1</version>
</dependency>

3.创建一个kafkaproducer KafkaProducerDemo

package com.example.demo.kafka;

import java.util.Properties;

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;

public class KafkaProducerDemo {

  private Producer<String, String> producer;

  public void start() {
    initKafkaProducer();
    sendMsgToKafka();
  }

  private void sendMsgToKafka() {
    ProducerRecord<String, String> record = new ProducerRecord<>("test_kafka_topic", "TestKafkaKey", "this is the test message");
    producer.send(record);
    producer.close();

  }

  private void initKafkaProducer() {
    Properties props = new Properties();
    //kafka集群
    props.put("bootstrap.servers", "localhost:9092");
    // 配置value的序列化类
    props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
    // 配置key的序列化类
    props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
    
    producer = new KafkaProducer<String, String>(props);
  }

  public static void main(String[] args) {
    new KafkaProducerDemo().start();
  }
}

4.创建一个kafkaproducer KafkaConsumerDemo

package com.example.demo.kafka;

import java.time.Duration;
import java.util.Arrays;
import java.util.Properties;

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;

public class KafkaConsumerDemo {

  private KafkaConsumer<String, String> consumer;

  public void start() {
    initKfkaConsumer();
    getMessageFromKafka();
  }

  private void getMessageFromKafka() {
    while (true) {
      ConsumerRecords<String, String> records = consumer.poll(Duration.ofSeconds(1));
      for (ConsumerRecord<String, String> record : records) {
        System.out.println("-------------------------------------------------------------------");
        System.out.printf("partition = %d offset = %d, key = %s, value = %s%n", record.partition(),record.offset(), record.key(), record.value());
      }
    }
  }

  private void initKfkaConsumer() {
    Properties props = new Properties();
    //kafka集群
    props.put("bootstrap.servers", "localhost:9092");
    //反序列化类，要和producer的序列化对应
    props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
    props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
    props.put("group.id", "test.group");

    consumer = new KafkaConsumer<>(props);
    //主题，从哪个主题取消息
    consumer.subscribe(Arrays.asList("test_kafka_topic"));

  }

  public static void main(String[] args) {
    new KafkaConsumerDemo().start();
  }

}