在 Spring Cloud Kafka 中,可以使用 MessageFilter 来实现消息过滤。MessageFilter 是一个接口,需要实现 apply
方法,该方法接收一个 ConsumerRecord 作为参数,返回一个 boolean 值,表示是否接受该消息。如果返回 true,则消息会被消费;如果返回 false,则消息会被忽略。
要实现消息过滤,你需要按照以下步骤操作:
MessageFilter
接口的类,并实现 apply
方法。在这个方法中,你可以根据需要编写过滤逻辑。例如,你可以根据消息的某个属性来决定是否接受该消息。import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.springframework.cloud.kafka.support.KafkaMessageFilter;
public class MyMessageFilter implements KafkaMessageFilter<String, String> {
@Override
public boolean apply(ConsumerRecord<String, String> record) {
// 在这里编写过滤逻辑
String value = record.value();
// 例如,只接受 value 包含 "example" 的消息
return value != null && value.contains("example");
}
}
MessageFilter
注册到 Kafka 消费者配置中。你需要注入 KafkaMessageFilter
Bean,并将其添加到 ConsumerFactory
的配置中。import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.common.serialization.StringDeserializer;
import org.springframework.beans.factory.annotation.Autowired;
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.support.serializer.ErrorHandlingDeserializer;
import org.springframework.kafka.support.serializer.JsonDeserializer;
import org.springframework.kafka.support.serializer.StringDeserializer;
import java.util.HashMap;
import java.util.Map;
@Configuration
public class KafkaConsumerConfig implements KafkaListenerConfigurer {
@Autowired
private MyMessageFilter myMessageFilter;
@Bean
public ConcurrentKafkaListenerContainerFactory<String, String> kafkaListenerContainerFactory() {
ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(consumerFactory());
return factory;
}
@Bean
public ConsumerFactory<String, String> consumerFactory() {
Map<String, Object> props = new HashMap<>();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
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);
props.put(ConsumerConfig.GROUP_ID_CONFIG, "my-group");
return new DefaultKafkaConsumerFactory<>(props);
}
@Override
public void configureKafkaListeners(KafkaListenerEndpointRegistrar registrar) {
registrar.setEndpoints(new MethodKafkaListenerEndpoint[]{
new MethodKafkaListenerEndpoint(
() -> new MyKafkaListener(),
"my-topic",
true,
null,
null,
String.class,
new ErrorHandlingDeserializer<>(new JsonDeserializer<>())
)
});
}
@Override
public void registerKafkaListenerEndpoint(KafkaListenerEndpointRegistry registry) {
registry.registerEndpoints(getKafkaListenerEndpoints());
}
private MethodKafkaListenerEndpoint[] getKafkaListenerEndpoints() {
// 这里应该返回你在 configureKafkaListeners 方法中注册的 Kafka 监听器端点
return new MethodKafkaListenerEndpoint[0];
}
}
现在,你的消费者将只消费 MyMessageFilter
过滤后的消息。当有新的消息到达时,apply
方法会被调用,只有满足过滤条件的消息才会被消费。
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