一、生产者，开启事务。

package com.cisdi.dsp.modules.metaAnalysis.rest.kafka2023;import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
import org.apache.kafka.common.serialization.StringSerializer;import java.util.Date;
import java.util.Properties;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;public class KafkaTest22 {public static void main(String[] args) {Properties properties= new Properties();properties.setProperty(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());properties.setProperty(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());properties.setProperty(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,"xx.xx.xx.xx:9092");properties.setProperty(ProducerConfig.ENABLE_IDEMPOTENCE_CONFIG, "true");properties.setProperty(ProducerConfig.RETRIES_CONFIG, "2");properties.setProperty(ProducerConfig.MAX_IN_FLIGHT_REQUESTS_PER_CONNECTION, "4");properties.setProperty(ProducerConfig.TRANSACTIONAL_ID_CONFIG, "myTransaction");KafkaProducer<String,String> kafkaProducer=new KafkaProducer<String, String>(properties);ProducerRecord<String,String> producerRecord=new ProducerRecord<>("study2024",0,"fff","hello sister,now is: "+ new Date());kafkaProducer.initTransactions();kafkaProducer.beginTransaction();try{Future<RecordMetadata> future = kafkaProducer.send(producerRecord);long offset = 0;try {offset = future.get().offset();} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}System.out.println(offset);Thread.sleep(60000);kafkaProducer.commitTransaction();} catch (Exception ex){kafkaProducer.abortTransaction();}kafkaProducer.close();}
}

二、消费者，设置隔离级别为"read_committed"

package com.cisdi.dsp.modules.metaAnalysis.rest.kafka2023;import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.clients.producer.ProducerConfig;
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.Arrays;
import java.util.Properties;
import java.util.concurrent.TimeUnit;public class KafkaTest23 {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,"testGroup");properties.setProperty(ConsumerConfig.ISOLATION_LEVEL_CONFIG, "read_committed");//properties.setProperty(ConsumerConfig.ISOLATION_LEVEL_CONFIG, "read_uncommitted");return properties;}public static void main(String[] args) {KafkaConsumer<String,String> myConsumer=new KafkaConsumer<String, String>(getProperties());String topic="study2024";myConsumer.subscribe(Arrays.asList(topic));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 is: "+record.offset());}}}
}

三、运行结果，按照上述配置，当生产者发送消息并从kafka broker获取到offset后就会sleep,在生产者sleep的时候，消费者是获取不到消息的，只有sleep完成并提交事务之后，消费者才会获取到消息