SpringBoot集成kafka-指定topic(主题)-partition(分区)-offset(偏移量)消费信息

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1、消费者

指定消费者读取配置文件中
topic = "$kafka.topic.name",groupId="${kafka.consumer.group}"下的数据。

package com.power.consumer;import com.power.model.User;
import com.power.util.JSONUtils;
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.kafka.support.Acknowledgment;
import org.springframework.kafka.support.KafkaHeaders;
import org.springframework.messaging.handler.annotation.Header;
import org.springframework.messaging.handler.annotation.Payload;
import org.springframework.stereotype.Component;import java.util.function.Consumer;@Component
public class EventConsumer { 	@KafkaListener(groupId="${kafka.consumer.group}",topicPartitions = {@TopicPartition(topic = "${kafka.topic.name}",partitions={"0","1","2"},partitionOffsets = {@PartitionOffset(partition="3",initialOffset = "3"),@PartitionOffset(partition="4",initialOffset = "3")})})public void onEvent5(String userJson,@Header(value=KafkaHeaders.RECEIVED_TOPIC) String topic,@Header(value=KafkaHeaders.RECEIVED_PARTITION_ID) String partition,ConsumerRecord<String,String> record,Acknowledgment ack){try {User user =JSONUtils.toBean(userJson,User.class);System.out.println("读取到的事件5："+user+",topic："+topic+",partition："+partition);//业务确认完成，给kafka服务器反馈确认ack.acknowledge();//手动确认消息，就是告诉kafka服务器，该消息我已经接收到了，默认情况下是自动确认//手动确认后，下次启动消费者，偏移量会从新的位置开始；没有手动确认，下次启动消费者，偏移量还是从老位置开始}catch (Exception e){e.printStackTrace();}}}

2、生产者

package com.power.producer;import com.power.model.User;
import com.power.util.JSONUtils;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.stereotype.Component;import javax.annotation.Resource;
import java.util.Date;@Component
public class EventProducer {@Resourceprivate KafkaTemplate<String,Object> kafkaTemplate;public void sendEvent3(){for (int i = 0; i < 25; i++) {User user = User.builder().id(i).phone("1567676767"+i).birthday(new Date()).build();String userJson = JSONUtils.toJSON(user);kafkaTemplate.send("helloTopic","k"+i,userJson);}}}

3、配置类

package com.power.config;import org.apache.kafka.clients.admin.NewTopic;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
public class KafkaConfig {@Beanpublic NewTopic newTopic(){return new NewTopic("helloTopic",5,(short)1);}
}

4、配置文件

spring:application:#应用名称name: spring-boot-02-kafka-base#kafka连接地址（ip+port）kafka:bootstrap-servers: <你的服务器IP>:9092#消费者consumer:auto-offset-reset: earliest#配置消息监听器listener:ack-mode: manual#自定义配置
kafka:topic:name: helloTopicconsumer:group: helloGroup

5、实体类

package com.power.model;import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;import java.util.Date;@Builder
@AllArgsConstructor
@NoArgsConstructor
@Data
public class User {private Integer id;private String phone;private Date birthday;}

6、工具类

package com.power.util;import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;public class JSONUtils {private static final ObjectMapper OBJECTMAPPER = new ObjectMapper();public static String toJSON(Object object){try {return OBJECTMAPPER.writeValueAsString(object);} catch (JsonProcessingException e) {throw new RuntimeException(e);}}public static <T> T toBean(String json,Class<T> clazz){try {return OBJECTMAPPER.readValue(json,clazz);} catch (JsonProcessingException e) {throw new RuntimeException(e);}}
}

7、测试类

package com.power;import com.power.producer.EventProducer;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;import javax.annotation.Resource;@SpringBootTest
public class SpringBoot02KafkaBaseApplication {@Resourceprivate EventProducer eventProducer;@Testvoid sendEvent5(){eventProducer.sendEvent5();}}

8、第一次测试（读取到19条信息）

总共读取1、2、3分区全部数据和4分区从4偏移量开始读，5分区从4开始读取。
6+4+6+3+0=19条数据。

9、第二次测试（读取到3条信息）

因为第一次读取已经记下来偏移量offset，即便在配置文件中指定了消费者从最开始读，也依然读取不到的。

此时可以通过修改组id来从头开始读取

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