pom 文件

    <dependencies>
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-clients</artifactId>
            <version>3.0.0</version>
        </dependency>
    </dependencies>

独立消费者案例（订阅主语）

在消费者API代码中，必须配置消费者id。命令行启动消费者不填写消费者组id会被自动填写随机得消费者组id

package com.longer.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) {
        //创建消费者的配置对象
        Properties properties=new Properties();
        //2、给消费者配置对象添加参数
        properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"hadoop100:9092");
        //配置序列化
        properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,StringDeserializer.class.getName());
        //配置消费者组（组名任意起名）必须
        properties.put(ConsumerConfig.GROUP_ID_CONFIG,"test");
        //创建消费者对象
        KafkaConsumer<String,String> kafkaConsumer=new KafkaConsumer<String, String>(properties);
        //注册要消费的主题
        ArrayList<String> topics=new ArrayList<>();
        topics.add("first");
        kafkaConsumer.subscribe(topics);
        while (true){
            //设置1s中消费一批数据
            ConsumerRecords<String,String> consumerRecords=kafkaConsumer.poll(Duration.ofSeconds(1));
            //打印消费到的数据
            for(ConsumerRecord<String,String> record:consumerRecords){
                System.out.println(record);
            }
        }
    }
}

发送的信息

消费信息（因为我发了好多次）

独立消费者案例

package com.longer.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.TopicPartition;
import org.apache.kafka.common.serialization.StringDeserializer;

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

public class CustomConsumerPartition {
    public static void main(String[] args) {
        Properties properties=new Properties();
        properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"hadoop100:9092");
        properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,StringDeserializer.class.getName());
        //配置消费者组（组名任意起名）必须
        properties.put(ConsumerConfig.GROUP_ID_CONFIG,"test");
        KafkaConsumer kafkaConsumer=new KafkaConsumer(properties);
        //消费某个注意的某个分区数据
        ArrayList<TopicPartition> topicPartitions=new ArrayList<>();
        topicPartitions.add(new TopicPartition("first",0));
        kafkaConsumer.assign(topicPartitions);
        while (true){
            ConsumerRecords<String,String> consumerRecords=kafkaConsumer.poll(Duration.ofSeconds(1));
            for (ConsumerRecord<String, String> consumerRecord : consumerRecords) {
                System.out.println(consumerRecord);
            }
        }
    }
}

发送信息发现只消费0分区的信息

消费者组案例

package com.longer.consumer.group;

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 CustomConsumer1 {
    public static void main(String[] args) {
        //创建消费者的配置对象
        Properties properties=new Properties();
        //2、给消费者配置对象添加参数
        properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"hadoop100:9092");
        //配置序列化
        properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
        properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG,StringDeserializer.class.getName());
        //配置消费者组（组名任意起名）必须
        properties.put(ConsumerConfig.GROUP_ID_CONFIG,"test");
        //创建消费者对象
        KafkaConsumer<String,String> kafkaConsumer=new KafkaConsumer<String, String>(properties);
        //注册要消费的主题
        ArrayList<String> topics=new ArrayList<>();
        topics.add("first");
        kafkaConsumer.subscribe(topics);
        while (true){
            //设置1s中消费一批数据
            ConsumerRecords<String,String> consumerRecords=kafkaConsumer.poll(Duration.ofSeconds(1));
            //打印消费到的数据
            for(ConsumerRecord<String,String> record:consumerRecords){
                System.out.println(record);
            }
        }
    }
}

复制三分，然后运行