kafka复习：（17）seekToBeginning的用法

从分区的开始进行消费，因为kafka会定期清理历史数据，所以分区开始的位移不一定为0。seekToBeginning只是从目前保留的数据中最小的offset进行消费

复制代码

package com.cisdi.dsp.modules.metaAnalysis.rest.kafka2023;

import org.apache.kafka.clients.consumer.*;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.common.PartitionInfo;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.apache.kafka.common.serialization.StringSerializer;

import java.time.Duration;
import java.time.temporal.TemporalUnit;
import java.util.*;
import java.util.concurrent.TimeUnit;
/*
从分区开头进行消费; seekToBeginning)
 */

public class KafkaTest14 {

    private static Properties getProperties(){
        Properties properties=new Properties();

        properties.setProperty(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        properties.setProperty(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        properties.setProperty(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"xx.xx.xx.xx:9092");
        properties.setProperty(ConsumerConfig.GROUP_ID_CONFIG,"testGroup12");
        //properties.setProperty(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG,"false");
        return properties;
    }
    public static void main(String[] args) {

        KafkaConsumer<String,String> myConsumer=new KafkaConsumer<String, String>(getProperties());
        myConsumer.subscribe(Arrays.asList("student"));
        Set<TopicPartition> topicPartitionSet = new HashSet<>();
        while(topicPartitionSet.size() == 0){
            ConsumerRecords<String,String> consumerRecords=myConsumer.poll(Duration.ofMillis(5000));
            topicPartitionSet = myConsumer.assignment();
        }

        myConsumer.seekToBeginning(topicPartitionSet);

        while(true){
            ConsumerRecords<String, String> consumerRecords = myConsumer.poll(Duration.ofMillis(5000));
            for(ConsumerRecord record: consumerRecords){
                System.out.println(record.value());
                System.out.println(record.offset());
            }

        }

    }
}