1、异步发送消息&回调

回调就是接收kafka的响应

1.1、pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.0.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <!-- Generated by https://start.springboot.io -->
    <!-- 优质的 spring/boot/data/security/cloud 框架中文文档尽在 => https://springdoc.cn -->
    <groupId>com.atguigu.kafka</groupId>
    <artifactId>kafka-producer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>kafka-producer</name>
    <description>kafka-producer</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-clients</artifactId>
            <version>3.0.0</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

1.2、KafkaProducer1.java

package com.atguigu.kafka.producer;
import org.apache.kafka.clients.producer.*;
import java.util.Properties;
public class KafkaProducer1 {

    /**
     * 主函数用于演示如何向Kafka的特定主题发送消息。
     *
     * @param args 命令行参数（未使用）
     */
    public static void main(String[] args) {
        // 初始化Kafka生产者配置
        Properties props = new Properties();
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "192.168.74.148:9092"); // 指定Kafka broker的地址和端口
        props.put("acks", "all"); // 确认消息写入策略
        props.put("retries", 0); // 消息发送失败时的重试次数
        props.put("linger.ms", 1); // 发送缓冲区等待时间
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer"); // 指定键的序列化器
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer"); // 指定值的序列化器

        // 创建Kafka生产者实例
        Producer<String, String> producer = new KafkaProducer<>(props);

        // 发送消息到主题"my_topic3"
        // 异步发送消息：不接收kafka的响应
        //producer.send(new ProducerRecord<String, String>("my_topic3",  "hello,1,2,3"));

        // 注释掉的循环代码块展示了如何批量发送消息
        //for (int i = 0; i < 100; i++)
        //    producer.send(new ProducerRecord<String, String>("my-topic", Integer.toString(i), Integer.toString(i)));


        producer.send(new ProducerRecord<String, String>("my_topic3",  "hello_3"),new Callback() {

            //消息发送成功，kafka broker ack 以后回调
            @Override
            public void onCompletion(RecordMetadata recordMetadata, Exception e) {
                //exception：如果有异常代表消息未能正常发送到kafka，没有异常代表消息发送成功：
                //此时kafka的消息不一定持久化成功（需要kafka生产者加配置）
                //RecordMetadata代表发送成功的消息的元数据
                System.out.println("recordMetadata.topic() = " + recordMetadata.topic());
                System.out.println("recordMetadata.partition() = " + recordMetadata.partition());
                System.out.println("msg offset = " + recordMetadata.offset());
                System.out.println("recordMetadata.timestamp() = " + recordMetadata.timestamp());

            }
        });
        // 关闭生产者实例
        producer.close();
    }
}

recordMetadata.topic() = my_topic3
recordMetadata.partition() = 1
msg offset = 1
recordMetadata.timestamp() = 1716976982243