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1 前言

在Spring Kafka中，可以通过配置拦截器来实现对生产者和消费者消息的拦截。拦截器可以用来记录日志、修改消息等等。

2 基于Kafka管理的拦截器

Kafka原生提供的拦截器接口是org.apache.kafka.clients.producer.ProducerInterceptor和
org.apache.kafka.clients.consumer.ConsumerInterceptor, 示例如下：

2.1 定义拦截器

生产者拦截器

import org.apache.kafka.clients.producer.ProducerInterceptor;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.TopicPartition;public class CustomProducerInterceptor implements ProducerInterceptor<String, String> {@Overridepublic ProducerRecord<String, String> onSend(ProducerRecord<String, String> record) {// 在发送消息之前操作System.out.println("Sending message: " + record.value());return record; // 继续发送}@Overridepublic void onAcknowledgement(RecordMetadata metadata, Exception exception) {}@Overridepublic void close() {// 资源清理}@Overridepublic void configure(Map<String, ?> configs) {// 可以在这里获取配置}
}

2.2 定义消费者拦截器

import org.apache.kafka.clients.consumer.ConsumerInterceptor;
import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.common.TopicPartition;public class CustomConsumerInterceptor implements ConsumerInterceptor<String, String> {@Overridepublic void configure(Map<String, ?> configs) {// 配置拦截器}@Overridepublic ConsumerRecords<String, String> onConsume(ConsumerRecords<String, String> records) {// 处理接收到的消息records.forEach(record -> {System.out.println("Consumed message: " + record.value());});return records;}@Overridepublic void onCommit(Map<TopicPartition, OffsetAndMetadata> offsets) {}@Overridepublic void close() {// 资源清理}
}

2.3 添加拦截器

方式一，通过工厂自定义器设置拦截器

import org.springframework.boot.autoconfigure.kafka.DefaultKafkaProducerFactoryCustomizer;
import org.springframework.boot.autoconfigure.kafka.DefaultKafkaConsumerFactoryCustomizer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.consumer.ConsumerConfig;@Component
public class KafkaProducerCustomizer implements DefaultKafkaProducerFactoryCustomizer, DefaultKafkaConsumerFactoryCustomizer {@Overridepublic void customize(DefaultKafkaProducerFactory<?, ?> producerFactory) {producerFactory.updateConfigs(Map.of(ProducerConfig.INTERCEPTOR_CLASSES_CONFIG, CustomProducerInterceptor.class.getName()));}@Overridepublic void customize(DefaultKafkaConsumerFactory<?, ?> consumerFactory) {consumerFactory.updateConfigs(Map.of(ConsumerConfig.INTERCEPTOR_CLASSES_CONFIG, CustomConsumerInterceptor.class.getName()));}
}

方式二，通过配置设置拦截器

spring:kafka:producer:properties:interceptor.classes: org.example.kafka.CustomProducerInterceptorconsumer:properties:interceptor.classes: org.example.kafka.CustomConsumerInterceptor

2.4 拦截器使用Spring容器中的Bean

上面的方法可以看到，拦截器由于没有在Spring容器中管理，则无法使用容器中其他Bean来做业务处理，那么可以另外一种策略达到让拦截器受Spring容器管理的需求, 已消息生产者拦截器为例：
Bean定义

@Component
public class MyComponent {public void checkMessage(String message) {System.out.println("Sending message: " + message);}
}

生产者拦截器

import org.apache.kafka.clients.producer.ProducerInterceptor;
import org.apache.kafka.clients.producer.Producer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.TopicPartition;public class CustomProducerInterceptor implements ProducerInterceptor<String, String> {private MyComponent myComponent;@Overridepublic ProducerRecord<String, String> onSend(ProducerRecord<String, String> record) {myComponent.checkMessage(record.value());return record; // 继续发送}@Overridepublic void onAcknowledgement(RecordMetadata metadata, Exception exception) {}@Overridepublic void close() {// 资源清理}@Overridepublic void configure(Map<String, ?> configs) {myComponent = configs.get("myComponent");}
}

设置拦截器

import org.springframework.boot.autoconfigure.kafka.DefaultKafkaProducerFactoryCustomizer;
import org.springframework.boot.autoconfigure.kafka.DefaultKafkaConsumerFactoryCustomizer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.consumer.ConsumerConfig;@Component
public class KafkaProducerCustomizer implements DefaultKafkaProducerFactoryCustomizer {@Autowiredprivate MyComponent myComponent;@Overridepublic void customize(DefaultKafkaProducerFactory<?, ?> producerFactory) {producerFactory.updateConfigs(Map.of("myComponent", myComponent,ProducerConfig.INTERCEPTOR_CLASSES_CONFIG, CustomProducerInterceptor.class.getName()));}
}

3 基于Spring-Kafka管理的拦截器

基于Kafka管理的拦截器对于消费消息的拦截只能做到批量消费级别（ConsumerRecords），如果要对单条消息拦截，可以使用Spring-Kafka提供的org.springframework.kafka.listener.RecordInterceptor接口。

3.1 单条消息拦截接口定义

由于此拦截器是受Spring容器管理的，所以可以通过@Component注解自动注入到容器中，进行自动拦截。

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.springframework.kafka.listener.RecordInterceptor;@Component
public class CustomRecordInterceptor implements RecordInterceptor<Object, Object> {@Overridepublic ConsumerRecord<Object, Object> intercept(ConsumerRecord<Object, Object> record) {System.out.println(record.topic());return record;}
}