如何将动态主题名称传递给@kafkalistener(环境变量中的主题 [英] How to pass dynamic topic name to @kafkalistener(topics from environment variable

问题描述

我正在写卡夫卡消费者 我想将环境变量主题名称传递给@kafkalistener(topics = topic

I AM WRITING A KAFKA CONSUMER I want to pass the environment variable topic name to @kafkalistener(topics = topic

 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());
   }
  }

topics =#{'$ {envProperties.getTopic()}'}" 在这条线 抛出错误.我的应用程序无法启动.必须根据环境变量动态设置此主题名称.

topics = "#{'${envProperties.getTopic()}'}" AT THIS LINE IT IS THROWING ERROR . MY APPLICATION FAILS TO START. hOW TO SET THIS TOPIC NAME DYNAMICALLY FROM ENVIRONMENT VARIABLE.

推荐答案

通常，您不能从声明SpEL的bean中引用字段或属性.但是，@KafkaListener具有支持它的特殊语法.

Normally, you can't reference fields or properties from the bean in which the SpEL is declared. However, @KafkaListener has special syntax to support it.

请参阅文档.

从版本2.1.2开始，SpEL表达式支持特殊的标记__listener，这是一个伪bean名称，代表该注释所在的当前bean实例.

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，如果将public EnvProperties getEnvProperties()添加到类中，则类似

So, if you add public EnvProperties getEnvProperties() to the class then something like

#{__listener.envProperties.topic}

应该工作.

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