java - 如何从环境变量将动态主题名称传递给@KafkaListener(topics)

Question

我正在编写一个 Kafka 消费者。我需要将环境变量主题名称传递给 @KafkaListener(topics = ...)。这是我到目前为止所尝试过的:

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.kafka.annotation.KafkaListener; 
 import org.springframework.stereotype.Service;

 @Service
 public class KafkaConsumer {

     @Autowired
     private EnvProperties envProperties;

     private final String topic = envProperties.getTopic();

     @KafkaListener(topics = "#{'${envProperties.getTopic()}'}", groupId = "group_id")
     public void consume(String message) {
        logger.info("Consuming messages " +envProperties.getTopic());
     }
}

我在 topics = "#{'${envProperties.getTopic()}'}" 行收到错误，应用程序无法启动。

如何从环境变量动态设置此主题名称？

Answer 1

通常，您不能引用声明 SpEL 的 bean 中的字段或属性。但是，@KafkaListener 有特殊的语法来支持它。

See the documentation .

Starting with version 2.1.2, the SpEL expressions support a special token __listener which is a pseudo bean name which represents the current bean instance within which this annotation exists.

因此，如果您将 public EnvProperties getEnvProperties() 添加到类中，则类似

#{__listener.envProperties.topic}

应该可以。