Kafka消费者 API（1）

1.需求：创建一个独立消费者，消费 first 主题中数据。

2.在IDEA创建包名：com.kafka.consumer

3.新建一个CustomConsumer类

package com.kafka.consumer;

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.serialization.StringDeserializer;

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

public class CustomConsumer {
    public static void main(String[] args) {
        //配置
        Properties properties = new Properties();
        //连接Kafka集群
        properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"hadoop102:9092");
        //反序列化
        properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,StringDeserializer.class.getName());
        //GroupId（必须配置）
        properties.put(ConsumerConfig.GROUP_ID_CONFIG,"test");
        //创建消费者对象
        KafkaConsumer<String, String> kafkaConsumer = new KafkaConsumer<>(properties);

        //topic数组
        ArrayList<String> topics = new ArrayList<>();
        topics.add("first");
        //订阅topic
        kafkaConsumer.subscribe(topics);
        //处理数据
        while (true){
            ConsumerRecords<String, String> consumerRecords = kafkaConsumer.poll(Duration.ofSeconds(1));
            for (ConsumerRecord<String, String> consumerRecord : consumerRecords) {
                System.out.println(consumerRecord);
            }
        }
    }
}

4.在 IDEA 中执行消费者程序。

5.在 Kafka 集群控制台，创建 Kafka 生产者，并输入数据。 

bin/kafka-console-producer.sh --bootstrap-server hadoop102:9092 --topic first

同时IDEA收到消息

sumerRecord(topic = first, partition = 1, leaderEpoch = 9, offset = 23, CreateTime = 1653112344357, serialized key size = -1, serialized value size = 5, headers = RecordHeaders(headers = [], isReadOnly = false), key = null, value = hello)