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1、指定offset消费

1.1、创建消费者监听器‘

package com.atguigu.spring.kafka.consumer.listener;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.kafka.annotation.PartitionOffset;
import org.springframework.kafka.annotation.TopicPartition;
import org.springframework.stereotype.Component;
@Component
public class MyKafkaPartitionListener {//初始化偏移量指定后，每次重启都会从该位置消费一轮，所以一般是调式解决问题时才使用@KafkaListener(topicPartitions = {@TopicPartition(topic = "my_topic1",partitionOffsets = {@PartitionOffset(partition = "0",initialOffset = "2")})}, groupId = "my_group1")public void onMessage1(ConsumerRecord<String, String> record) {System.out.println("my_group1消费者1获取到消息：topic = "+ record.topic()+"，partition:"+record.partition()+"，offset = "+record.offset()+"，key = "+record.key()+"，value = "+record.value());}}

1.2、application.yml配置

server:port: 8120# v1
spring:Kafka:bootstrap-servers: 192.168.74.148:9095,192.168.74.148:9096,192.168.74.148:9097consumer:# read-committed读事务已提交的消息 解决脏读问题isolation-level: read-committed # 消费者的事务隔离级别：read-uncommitted会导致脏读，可以读取生产者事务还未提交的消息# 消费者是否自动ack ：true自动ack 消费者获取到消息后kafka提交消费者偏移量enable-auto-commit: true # 消费者提交ack时多长时间批量提交一次auto-commit-interval: 1000# 消费者第一次消费主题消息时从哪个位置开始auto-offset-reset: earliest  #指定Offset消费:earliest | latest | nonekey-deserializer: org.apache.kafka.common.serialization.StringDeserializervalue-deserializer: org.apache.kafka.common.serialization.StringDeserializer

1.3、使用 Java代码 创建 主题 my_topic1 并建立3个分区并给每个分区建立3个副本

package com.atguigu.spring.kafka.consumer.config;
import org.apache.kafka.clients.admin.NewTopic;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.config.TopicBuilder;
@Configuration
public class MyKafkaConfig {@Beanpublic NewTopic springTestPartitionTopic() {return TopicBuilder.name("my_topic1") //主题名称.partitions(3) //分区数量.replicas(3) //副本数量.build();}
}

1.4、创建生产者发送消息

package com.atguigu.spring.kafka.consumer;import jakarta.annotation.Resource;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.kafka.core.KafkaTemplate;@SpringBootTest
class SpringKafkaConsumerApplicationTests {@ResourceKafkaTemplate kafkaTemplate;@Testvoid contextLoads() {for (int i = 0; i < 10; i++) {kafkaTemplate.send("my_topic1",i%3,"", "指定分区消费"+i);}}}

1.4.1、分区0中的数据

[[{"partition": 0,"offset": 0,"msg": "指定offset消费0","timespan": 1717660785962,"date": "2024-06-06 07:59:45"},{"partition": 0,"offset": 1,"msg": "指定offset消费3","timespan": 1717660785974,"date": "2024-06-06 07:59:45"},{"partition": 0,"offset": 2,"msg": "指定offset消费6","timespan": 1717660785975,"date": "2024-06-06 07:59:45"},{"partition": 0,"offset": 3,"msg": "指定offset消费9","timespan": 1717660785975,"date": "2024-06-06 07:59:45"}]
]

1.5、创建SpringBoot启动类

package com.atguigu.spring.kafka.consumer;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;// 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
@SpringBootApplication
public class SpringKafkaConsumerApplication {public static void main(String[] args) {SpringApplication.run(SpringKafkaConsumerApplication.class, args);}}

1.6、屏蔽 kafka debug 日志 logback.xml

<configuration>　　　　　　<!-- 如果觉得idea控制台日志太多，src\main\resources目录下新建logback.xml
屏蔽kafka debug --><logger name="org.apache.kafka.clients" level="debug" />
</configuration>

1.7、引入spring-kafka依赖

<?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</groupId><artifactId>spring-kafka-consumer</artifactId><version>0.0.1-SNAPSHOT</version><name>spring-kafka-consumer</name><description>spring-kafka-consumer</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.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka</artifactId></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

1.8、消费者控制台：

  .   ____          _            __ _ _/\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \\\/  ___)| |_)| | | | | || (_| |  ) ) ) )'  |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/=/_/_/_/:: Spring Boot ::                (v3.0.5)my_group1消费者1获取到消息：topic = my_topic1，partition:0，offset = 2，key = ，value = 指定offset消费6
my_group1消费者1获取到消息：topic = my_topic1，partition:0，offset = 3，key = ，value = 指定offset消费9

此时如果重新启动 SpringKafkaConsumerApplication 消费者还是会消费数据，重复消费

  .   ____          _            __ _ _/\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \\\/  ___)| |_)| | | | | || (_| |  ) ) ) )'  |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/=/_/_/_/:: Spring Boot ::                (v3.0.5)my_group1消费者1获取到消息：topic = my_topic1，partition:0，offset = 2，key = ，value = 指定offset消费6
my_group1消费者1获取到消息：topic = my_topic1，partition:0，offset = 3，key = ，value = 指定offset消费9