Java 获取Kafka的topic的offset

要获取Kafka的topic的offset，可以使用KafkaConsumer类中的方法。以下是Java代码示例：

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.common.TopicPartition;

import java.time.Duration;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

public class KafkaOffsetGetter {

    public static void main(String[] args) {

        // Kafka consumer configuration
        Properties props = new Properties();
        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
        props.put(ConsumerConfig.GROUP_ID_CONFIG, "my-group");
        props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");

        // Create Kafka consumer
        KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);

        // Assign topic partitions
        List<TopicPartition> partitions = new ArrayList<>();
        TopicPartition partition0 = new TopicPartition("my-topic", 0);
        TopicPartition partition1 = new TopicPartition("my-topic", 1);
        partitions.add(partition0);
        partitions.add(partition1);
        consumer.assign(partitions);

        // Seek to beginning of topic
        consumer.seekToBeginning(partitions);

        // Print offset for each partition
        while (true) {
            ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(100));
            for (ConsumerRecord<String, String> record : records) {
                System.out.println("Partition: " + record.partition() +
                        ", Offset: " + record.offset() +
                        ", Value: " + record.value());
            }
        }
    }
}

在上面的代码中，我们创建了一个KafkaConsumer实例，并使用assign()方法指定要消费的topic和分区，然后使用seekToBeginning()方法将消费者定位到该topic的开头。接着，我们使用poll()方法从Kafka中获取一批记录，并遍历这些记录以获取每个分区的当前offset。