一、消费者组案例

1.1、案例需求

• 测试同一个主题的分区数据，只能由一个消费者组中的一个消费。如下图所示：
  

1.2、案例代码

复制一份基础消费者的代码，在 IDEA 中同时启动，即可启动同一个消费者组中的两个消费者。

1.2.1、消费者1代码

• 代码

  package com.xz.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 CustomConsumer1 {
  
      public static void main(String[] args) {
  
          // 配置
          Properties properties = new Properties();
  
          // 连接 bootstrap.servers
          properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.136.27:9092,192.168.136.28:9092,192.168.136.29:9092");
  
          // 反序列化
          properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
          properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
  
          // 配置消费者组id
          properties.put(ConsumerConfig.GROUP_ID_CONFIG,"test5");
  
          // 设置分区分配策略
          properties.put(ConsumerConfig.PARTITION_ASSIGNMENT_STRATEGY_CONFIG,"org.apache.kafka.clients.consumer.StickyAssignor");
  
          // 1 创建一个消费者  "", "hello"
          KafkaConsumer<String, String> kafkaConsumer = new KafkaConsumer<>(properties);
  
          // 2 订阅主题 first
          ArrayList<String> topics = new ArrayList<>();
          topics.add("firstTopic");
          kafkaConsumer.subscribe(topics);
  
          // 3 消费数据
          while (true){
              //每一秒拉取一次数据
              ConsumerRecords<String, String> consumerRecords = kafkaConsumer.poll(Duration.ofSeconds(1));
              //输出数据
              for (ConsumerRecord<String, String> consumerRecord : consumerRecords) {
                  System.out.println(consumerRecord);
              }
  
              kafkaConsumer.commitAsync();
          }
      }
  }
  

1.2.2、消费者2代码

• 代码

  package com.xz.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 CustomConsumer2 {
  
      public static void main(String[] args) {
  
          // 0 配置
          Properties properties = new Properties();
  
          // 连接 bootstrap.servers
          properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.136.27:9092,192.168.136.28:9092,192.168.136.29:9092");
  
          // 反序列化
          properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
          properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
  
          // 配置消费者组id
          properties.put(ConsumerConfig.GROUP_ID_CONFIG,"test5");
          // 设置分区分配策略
          properties.put(ConsumerConfig.PARTITION_ASSIGNMENT_STRATEGY_CONFIG,"org.apache.kafka.clients.consumer.StickyAssignor");
  
          // 1 创建一个消费者  "", "hello"
          KafkaConsumer<String, String> kafkaConsumer = new KafkaConsumer<>(properties);
  
          // 2 订阅主题 first
          ArrayList<String> topics = new ArrayList<>();
          topics.add("firstTopic");
          kafkaConsumer.subscribe(topics);
  
          // 3 消费数据
          while (true){
  
              ConsumerRecords<String, String> consumerRecords = kafkaConsumer.poll(Duration.ofSeconds(1));
  
              for (ConsumerRecord<String, String> consumerRecord : consumerRecords) {
                  System.out.println(consumerRecord);
              }
          }
      }
  }
  
  

1.2.3、消费者3代码

• 代码

  package com.xz.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 CustomConsumer3 {
  
      public static void main(String[] args) {
  
          // 配置
          Properties properties = new Properties();
  
          // 连接 bootstrap.servers
          properties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.136.27:9092,192.168.136.28:9092,192.168.136.29:9092");
  
          // 反序列化
          properties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
          properties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
  
          // 配置消费者组id
          properties.put(ConsumerConfig.GROUP_ID_CONFIG,"test5");
  
          // 设置分区分配策略
          properties.put(ConsumerConfig.PARTITION_ASSIGNMENT_STRATEGY_CONFIG,"org.apache.kafka.clients.consumer.StickyAssignor");
  
          // 1 创建一个消费者  "", "hello"
          KafkaConsumer<String, String> kafkaConsumer = new KafkaConsumer<>(properties);
  
          // 2 订阅主题 first
          ArrayList<String> topics = new ArrayList<>();
          topics.add("firstTopic");
          kafkaConsumer.subscribe(topics);
  
          // 3 消费数据
          while (true){
              //每一秒拉取一次数据
              ConsumerRecords<String, String> consumerRecords = kafkaConsumer.poll(Duration.ofSeconds(1));
              //输出数据
              for (ConsumerRecord<String, String> consumerRecord : consumerRecords) {
                  System.out.println(consumerRecord);
              }
  
              kafkaConsumer.commitAsync();
          }
      }
  }
  

1.2.4、生产者代码

• 代码

  package com.xz.kafka.producer;
  
  import org.apache.kafka.clients.producer.*;
  import org.apache.kafka.common.serialization.StringSerializer;
  import java.util.Properties;
  
  public class CustomProducerCallback {
  
      public static void main(String[] args) throws InterruptedException {
  
          //1、创建 kafka 生产者的配置对象
          Properties properties = new Properties();
  
          //2、给 kafka 配置对象添加配置信息：bootstrap.servers
          properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG,"192.168.136.27:9092,192.168.136.28:9092,192.168.136.29:9092");
  
          //3、指定对应的key和value的序列化类型 key.serializer value.serializer
          properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
          properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG,StringSerializer.class.getName());
  
          //4、创建 kafka 生产者对象
          KafkaProducer<String, String> kafkaProducer = new KafkaProducer<>(properties);
  
          //5、调用 send 方法,发送消息
          for (int i = 0; i < 200; i++) {
              kafkaProducer.send(new ProducerRecord<>("firstTopic", "hello kafka" + i), new Callback() {
                  @Override
                  public void onCompletion(RecordMetadata metadata, Exception exception) {
                      if (exception == null){
                          System.out.println("主题： "+metadata.topic() + " 分区： "+ metadata.partition());
                      }
                  }
              });
              Thread.sleep(2);
          }
  
          // 3 关闭资源
          kafkaProducer.close();
      }
  }
  

1.3、测试

• 在 Kafka 集群控制台，创建firstTopic主题

  bin/kafka-topics.sh --bootstrap-server 192.168.136.27:9092 --create --partitions 3 --replication-factor 1 --topic firstTopic
  

  

• 首先，在 IDEA中分别启动消费者1、消费者2和消费者3代码
  

• 然后，在 IDEA中分别启动生产者代码
  

• 在 IDEA 控制台观察消费者1、消费者2和消费者3控制台接收到的数据，如下图所示：
  由下图可知：3个消费者在消费不同分区的数据