springboot 整合 kafka 如何實現消息過濾

在 Spring Boot 中整合 Kafka 并實現消息過濾，可以通過以下步驟來完成：

1. 添加依賴

在 pom.xml 文件中添加 Kafka 和 Spring Boot Kafka 相關的依賴：

<dependencies>
    <!-- Spring Boot Kafka Starter -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-kafka</artifactId>
    </dependency>
</dependencies>

2. 配置 Kafka

在 application.yml 或 application.properties 文件中配置 Kafka 相關屬性：

spring:
  kafka:
    bootstrap-servers: localhost:9092
    consumer:
      group-id: my-group
      auto-offset-reset: earliest
      key-deserializer: org.apache.kafka.common.serialization.StringDeserializer
      value-deserializer: org.apache.kafka.common.serialization.StringDeserializer

3. 創建消息過濾器

創建一個實現 ConsumerInterceptor 接口的類，用于實現消息過濾邏輯：

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.ConsumerInterceptor;
import org.apache.kafka.clients.consumer.OffsetAndMetadata;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import java.util.Collections;
import java.util.List;

@Component
public class MessageFilterInterceptor implements ConsumerInterceptor<String, String> {

    @Value("${kafka.topic}")
    private String topic;

    @Override
    public List<ConsumerRecord<String, String>> onConsume(ConsumerRecords<String, String> records) {
        List<ConsumerRecord<String, String>> filteredRecords = Collections.emptyList();
        for (ConsumerRecord<String, String> record : records) {
            if (filter(record)) {
                filteredRecords.add(record);
            }
        }
        return filteredRecords;
    }

    @Override
    public void onAcknowledge(OffsetAndMetadata offsetAndMetadata) {
        // 無需實現
    }

    @Override
    public void onCommitOffsets(OffsetAndMetadata offsetAndMetadata) {
        // 無需實現
    }

    @Override
    public void onError(Exception e) {
        // 無需實現
    }

    private boolean filter(ConsumerRecord<String, String> record) {
        // 實現消息過濾邏輯，例如根據消息內容判斷是否過濾
        String messageValue = record.value();
        return !messageValue.contains("filtered");
    }
}

4. 配置 Kafka 消費者

創建一個配置類，用于配置 Kafka 消費者，并將自定義的消息過濾器添加到消費者配置中：

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.annotation.KafkaListenerConfigurer;
import org.springframework.kafka.config.ConcurrentKafkaListenerContainerFactory;
import org.springframework.kafka.config.KafkaListenerEndpointRegistrar;
import org.springframework.kafka.config.KafkaListenerEndpointRegistry;
import org.springframework.kafka.listener.ConcurrentMessageListenerContainer;
import org.springframework.kafka.listener.config.MethodKafkaListenerEndpoint;
import org.springframework.kafka.listener.config.MethodKafkaListenerEndpointRegistrar;
import org.springframework.kafka.listener.config.KafkaListenerEndpoint;

import java.util.HashMap;
import java.util.Map;

@Configuration
public class KafkaConsumerConfig implements KafkaListenerConfigurer {

    @Value("${kafka.bootstrap-servers}")
    private String bootstrapServers;

    @Bean
    public ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory<>();
        factory.setConsumerFactory(consumerFactory());
        return factory;
    }

    @Bean
    public ConsumerFactory<String, String> consumerFactory() {
        return new DefaultKafkaConsumerFactory<>(consumerConfigs());
    }

    @Bean
    public Map<String, Object> consumerConfigs() {
        Map<String, Object> props = new HashMap<>();
        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
        props.put(ConsumerConfig.GROUP_ID_CONFIG, "my-group");
        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
        return props;
    }

    @Override
    public void configureKafkaListeners(KafkaListenerEndpointRegistrar registrar) {
        MethodKafkaListenerEndpointRegistrar methodRegistrar = new MethodKafkaListenerEndpointRegistrar(registrar);
        methodRegistrar.setBean(this);
        methodRegistrar.setMethod(this.getClass().getDeclaredMethods()[0]);
        methodRegistrar.setTopics(Collections.singletonList(this.topic()));
        methodRegistrar.setConsumerFactory(consumerFactory());
        methodRegistrar.setInterceptor(new MessageFilterInterceptor());
        methodRegistrar.registerEndpoints();
    }

    @Bean
    public String topic() {
        return "my-topic";
    }
}

5. 創建 Kafka 監聽器

創建一個類，用于處理接收到的消息：

import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.stereotype.Component;

@Component
public class KafkaMessageListener {

    @KafkaListener(topics = "${kafka.topic}", groupId = "${kafka.consumer.group-id}")
    public void listen(String message) {
        System.out.println("Received message: " + message);
    }
}

現在，當消費者接收到消息時，MessageFilterInterceptor 會先對消息進行過濾，只有符合條件的消息才會被 KafkaMessageListener 處理。