[CAMEL-15686] Enable EndpointDSL with simple expressions within an Endpoint Builder bean

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Cannot Reproduce
• Fix Version/s: 3.7.0
• Component/s: camel-endpointdsl

Environment

Experienced with 

• Camel 3.4.4
• Spring Boot 2.3.4

• Estimated Complexity: Unknown
• Assignee: Claus Ibsen
• Reporter: Franky Georg
• Created: 13/Oct/20 23:28
• Updated: 03/Nov/20 08:18
• Resolved: 03/Nov/20 08:18

Description

Injecting an EndpointProducerBuilder bean that uses a simple expression causes an exception.

@Configuration
public class MyTestRoute extends EndpointRouteBuilder {
   private static final String MY_TOPIC = "testTopic";

   @Autowired
   private EndpointProducerBuilder myKafkaBean;

   @Override
   public void configure() {
      from(timer("myTimer").repeatCount(1))
            .setBody(constant("THIS IS A TEST MESSAGE"))
            .setProperty("destination2", constant(MY_TOPIC))
            .to("direct:publish-to-kafka2")
      ;

      from("direct:publish-to-kafka2")
            .toD(myKafkaBean)
      ;

      from(kafka(MY_TOPIC))
            .log("Received: ${body}")
      ;
   }

   @Bean
   public EndpointProducerBuilder myKafkaBean() {
      return kafka("${exchangeProperty.destination2}");
   }
}

Exception from org.apache.kafka.clients.Metadata:

Metadata response reported invalid topics [${exchangeProperty.destination}]

I don't have to use the bean for the error to manifest, it's enough to @Autowire it.

 

It does work for static endpoints:

    return kafka("myTopic"); // This works fine from an EndpointProducerBuilder bean

And it does work for dynamic endpoints in URI form:

    return "kafka:${exchangeProperty.destination}"; // This works fine but you lose type safety

 

Creating beans like this is useful for unit testing as they can be overridden to return mock/direct/whatever-is-useful, without first creating the original endpoint, which can significantly reduce execution time.