@SentTo如何将消息发送到相关主题? [英] How @SentTo sends the message to related topic?

问题描述

我在Rest控制器中使用ReplyingKafkaTemplate返回同步响应.我还要设置标题REPLY_TOPIC.对于侦听器微服务部分，

I am using ReplyingKafkaTemplate in my Rest controller to return the synchronous response. I am also setting header REPLY_TOPIC. For listener microservice part,

 @KafkaListener(topics = "${kafka.topic.request-topic}")
 @SendTo
 public Model listen(Model<SumModel,SumResp> request) throws InterruptedException {

   SumModel model = request.getRequest();
   int sum = model.getNumber1() + model.getNumber2();

   SumResp resp = new SumResp(sum);
   request.setReply(resp);

   request.setAdditionalProperty("sum", sum);
   return request;
 }

我的问题是，@sentTo批注如何将消息发布到标题中提供的主题.应该有一个KafkaTemplate bean还是不需要它?由于我们只是在不使用任何KafkaTemplate或ReplyingKafkaTemplate bean的情况下返回消息.

My question is, How @sentTo annotation manage to publish the message to the topic provided in the header. There should be a KafkaTemplate bean or it does not need it? As we are just returning the message without using any KafkaTemplate or ReplyingKafkaTemplate bean.

没有任何kafka模板，它可以工作还是需要KafkaTemplate或ReplyingKafkaTemplate bean?

Without any kafka template does it work or does it require KafkaTemplate or ReplyingKafkaTemplate beans?

谢谢

推荐答案

是的，使用模板发送回复...

Yes, a template is used to send the reply...

Assert.state(replyTopic == null || this.replyTemplate != null,
        "a KafkaTemplate is required to support replies");

如果应用程序上下文中只有一个模板，Spring Boot会自动将模板连接到侦听器容器工厂.

Spring Boot automatically wires a template into the listener container factory if there is exactly one in the application context.

map.from(this.replyTemplate).to(factory::setReplyTemplate);

如果上下文中还没有模板，启动也会自动配置模板.

Boot also auto configures a template if there is not one already in the context.

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